16 ms·

Why is no one signing their emails?

270 points by Karrot_Kream 8y ago

pw6hv 8y ago
I was so surprised when I received a signed email by Postfinance, my bank here in Switzerland. I really think it would be very beneficial if all major providers would start to use that. At first not many people would check the signature, but if then this takes momentum probably all major email provider will start to show an icon telling that the email is signed and verified. Just like Gmail shows when an email was received through a secure channel (TLS).
seanwilson 8y ago
I think if Gmail decided to implement email signing today as a prominent feature where they show a big warning for all non-signed emails the user demand for it would happen pretty quick e.g. WARNING: You cannot trust this email was sent from who it says it's from, the email have been modified in transit, and the email may have been read by hackers in transit Similar to how Chrome started showing non-HTTPS sites as "Not secure".
- organsnyder 8y ago
  They already show this information, but it's not prominent (I had to view the sender details to see it). https://support.google.com/mail/answer/6330403 https://support.google.com/mail/answer/6330403
  - mankyd 8y ago
    Encryption and signing are different things here. Encryption in this case means that the contents of the email are encrypted between Google's servers and the recipient's servers. i.e. preventing snooping. Signing verifies that the contents of the email itself have been authenticated by the author. I.e. prevent spoofing.
    - organsnyder 8y ago
      Their documentation doesn't mention signing specifically, but wouldn't S/MIME include signing?
      - mankyd 8y ago
        Signing on behalf of the server, maybe, but gmail in no way supports/encourages having the actual author sign their messages, to my knowledge.
andrewstuart 8y ago
It's surprising to me that anyone could think that email signing was even vaguely in the ballpark of being comprehensible to the ordinary person.
- droithomme 8y ago
  It can be a pain even for the dedicated expert.
- mikekchar 8y ago
  Conceptually it's not hard at all. "When you send an email there is no proof that it came from you. It is easy to fake emails. When you press this button, it will 'digitally sign' the email. Now people can tell that it comes from you." It's the key exchange that's difficult. However, as the blog rightly points out, having companies sign their emails would be a massive step in the right direction. Every ordinary person uses an email service. If that email service handled the key exchange for those companies the it would be truly wonderful. It doesn't even need to be that difficult given that these companies almost certainly have certificates for their websites. Then all the service provider has to do is put this nice message when delivering the email: "This email was not signed by the company that it claims to be sent from. Beware." Not in any way difficult for an ordinary person to understand.
  - duiker101 8y ago
    I think even conceptually it's hard. Your email address is your proof. You have to use a password to access it so it must mean only you can send emails with it.
    - stephenr 8y ago
      I can write your name as the sender on a physical letter and send it, and I can do the same thing with an email. There, conceptually it's explained, to anyone who has any concept of what "writing" is.
      - 8y ago
gudok 8y ago
Maybe it is because major email services already do good enough job of filtering spam/phishing emails? And yes, we already have DKIM.
- Carpetsmoker 8y ago
  (I am the author of this article, looks like someone posted it here before I got the chance) If they were, phishing would be a thing of the past; but it's not. In addition it's a lot harder to filter out targeted spear phishing with spam filters. Spam filtering is certainly useful – as are other measures such as the malicious website list that most browsers have – but it seems to me that adding extra guarantees such as signing would be a good thing? DKIM is useful, but also limited. It just detects forgeries of From address and such. Ideally email signing should be like https: if it's not https then you shouldn't trust it. DKIM can perhaps fill this role; but the current implementations don't; they just add some score to the spam-check.
  - deleted 8y ago
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  - evgen 8y ago
    You are begging the question by assuming that a signature on an email message proves anything useful to the recipient when the facts on the ground show this not to be the case. It is not harder to conduct phishing with email signatures, and the fact that such phishing campaigns have no problem putting TLS certs on their phishing sites is a simple existence proof of this fact. Email signatures does not impact spam in any significant manner beyond existing measures to prevent domain name forgery in the header. Spam email signed by joe@cheap-ray-bans.com does not stop being spam because it is signed and the signature provides no useful signal to spam filtering tools. The difference between an email signature and a TLS cert on a web site is that in the latter case the user is making an effort to connect to a specific site and the certificate ensures that they are in fact connecting to paypaaaaal.com even if other means were used to misdirect them to this site. With email there are two problems to be addressed, transport privacy/security (a sender problem) and unsolicited email (a recipient problem) and signatures are only useful in ensuring integrity of the former and do nothing for the latter.
deleted 8y ago
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elcomet 8y ago
Maybe one reason is because it is a hassle to check the signature of someone you didn't have already in your contact list ? How do you know it's not a fake signature ? Certainly you have to look at their website and find the key. But what if this person doesn't have a website ?
- Tepix 8y ago
  With S/MIME the certificate (signed by a known CA) is included in the email.
- Carpetsmoker 8y ago
  for S/MIME you don't need this; it's just a CA chain like HTTPS (for better or worse). For PGP I mentioned some possible options: > PGP could also be used; we can bypass much of the key exchange dilemma by just shipping email clients with keys for large organisations (PayPal, Google, etc.); like browsers do with some certificates. Or publish the keys on a DNS record. Even just publishing them on your website (or, if you’re a bank, in local branches etc.) so people can manually add them to their keyrings is a lot better than not signing anything at all!
mothsonasloth 8y ago
The average Joey Bloggs is just coming to terms with fake news and how to make their social media pages more private. PGP is not user friendly though and will never reach wide adoption until it's made easier or someone develops a service for it.
- Carpetsmoker 8y ago
  PGP doesn't need to be user-friendly just to verify signatures. It's like verifying your Linux distro's package system: all of them sign their packages (usually with PGP) and they get verified on installation, but as an end-user I never see it. And yes, PGP is hard, but only if I want to add signatures to my emails, or use it for encryption. But that's a different use case than what I wrote about here. I think this is exactly the sort of confusion I intended with: > Confusion between every-day “random person A emails random person B”-usage versus “large company with millions of users sends thousands of emails daily”-usage.
  - BeetleB 8y ago
    >But that's a different use case than what I wrote about here. I find it amusing that the problem in the HN threads isn't that they know too little, it's that they know too much. They've seen arguments against PGP for years, and are having trouble processing the post in any way that is different from the "usual" PGP use cases they've seen. I'm seeing comments arguing that the user can't understand concepts of web of trust, or will get fooled by Paypals.com's signature, etc.
  - deleted 8y ago
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- ajcodez 8y ago
  Isn’t that service Keybase?
  - Leace 8y ago
    Keybase diverged so significantly from PGP that one wouldn't say "Keybase is PGP with good UX". You can say "Keybase is encryption with good UX" though.
z3t4 8y ago
There's nothing stopping spammers from signing their spam. The pain point with signing and encryption is key rotation. One problem is that both scammers and banks themselves use domains like paypal.accepournewtos.com or paypal.usersurvey.com and paypal@ourmailservice.randomdomain.com
- Carpetsmoker 8y ago
  > There's nothing stopping spammers from signing their spam. The pain point with signing and encryption is key rotation. Yes, but those signatures can't be verified. I understand this is tricky problem; how do we prevent people from simply clicking "accept this unknown key"? I'm not sure; but not every user is a blubbering idiot, and "unknown signature" strikes me as a lot better UX than "carefully look for spelling errors or misleading domain names".
  - rebuilder 8y ago
    Why couldn't they get a certificate for accepourtos.com?
  - chx 8y ago
    https://twitter.com/miradoreltd/status/843877685675868160 https://twitter.com/miradoreltd/status/843877685675868160 adopted from http://blog.johnath.com/images/snotweasel.png http://blog.johnath.com/images/snotweasel.png [Transcription: Windows XP error dialog with the yellow triangle - title "Something happened and you need to click OK to get on with things." details: "Certificate mismatch security identification administration communication intercept liliputian snotweasel foxtrot omegaforce." then you have a button saying Technical Crap and three radio buttons 1) More technical crap 2) Hoyvin-Glayvin 3) Launch photon torpedoes and then OK and Cancel buttons.]
    - riffraff 8y ago
      I will argue that something like the chrome untrusted certificate warning will scare away most of the users. https://i.stack.imgur.com/r0iOf.png https://i.stack.imgur.com/r0iOf.png
paxys 8y ago
Sure an email from Paypal.com can be signed or encrypted, but so can an identical one from Paypa1.com. How are users more protected in this case? In fact a big "sender verified" message in the email client for the latter email will cause a lot more phishing.
- c256 8y ago
  Web browsers already implement a ‘near miss that’s probably intentionally confusing” check on domains, and the code is readily extracted and shared (I know about it because someone extracted it and added it to Emacs a couple years ago). This seems like one of those cases where more large infrastructure people need to say “don’t let the perfect be the enemy of the good”.
  - joombaga 8y ago
    > Web browsers already implement a ‘near miss that’s probably intentionally confusing” check on domains, What do they do with the information?
    - c256 8y ago
      For Emacs (and its web browsers, email clients, etc) this comes up in a concept of “confusables” strings that could easily be mistaken for other strings, usually as a result of Unicode tricks (multiple similar code points from different scripts, or composed versus combined characters, or sometimes ugly tricks with LtR/RtL markers. The code added to emacs was. A library that could be used to detect these probably-misleading tricks, but they didn’t implement a policy for them. The uses I saw of the library fell into the sort of “Danger, Will Robinson! This looks like it might be malicious” type warnings that can be found in most browsers these days.
- pasta 8y ago
  True, but two different issues. The domain part of signing is now being solved by DNS (PTR, SPF, Caller-ID). But signing still it has it's use because you also know the user exists. And encryption is very useful because most emails are stored as plain text on some server.
Tepix 8y ago
We need free S/MIME certificates with decent validity periods (remember, you have to keep around all certificates you've ever used!). Webmail (which a lot of people use) is also not ideal for dealing with certicates. You more or less have to trust the mail provider with your private keys. There are just countless attack vectors. Finally, it's quite technical to get a certificate, copy it to all your devices that have an email client and configure them.
- Carpetsmoker 8y ago
  I am not intimately familiar with the finances of PayPal, Google, Facebook, or Amazon.com, but I suspect they may be able to afford an S/MIME certificate. Perhaps even two or three! > Webmail (which a lot of people use) is also not ideal for dealing with certicates. You more or less have to trust the mail provider with your private keys. There are just countless attack vectors. You are already trusting the email provider with everything. What's so bad with trusting them to verify a signature, too? We're not communicating state secrets over encrypted email here; we're just verifying the signature on "PayPal sent you a message, click here to view it"-kind of emails.
  - rebuilder 8y ago
    But the signature doesn't tell you the sender is the org they claim to be, because how would the verification system know who the sender says they are?
- JorgeGT 8y ago
  In my country anyone can get a free certificate from the Royal Mint. But few people uses them for email due to lack of support from webmail providers, as you say.
  - rurounijones 8y ago
    Which country is this and do you have a link? sounds interesting.
emilsedgh 8y ago
I sign my emails with PGP all the time. One of the problems I noticed is that the signature ends up as an attachment and that confuses the hell out of many people. Did you send me an attachment? What was that file I couldn't open it!
- p4bl0 8y ago
  I do the same and I get that a lot. Most of the time from people using Outlook.
- Carpetsmoker 8y ago
  Once (or rather, if) PGP gains some traction this problem will disappear; email clients will improve the UX to show a specialised "PGP signed" box and hide the attachment.
  - r_c_a_d 8y ago
    That's what I thought. But after 5 years I gave up and do not sign my emails any more.
  - dredmorbius 8y ago
    It's been 23 years since MIME Security with Pretty Good Privacy (PGP) was proposed. http://www.faqs.org/rfcs/rfc2015.html http://www.faqs.org/rfcs/rfc2015.html I'm starting to think that someone really doesn't want this to happen.
edoo 8y ago
I always thought the best webmail would be one that uses PGP in purely browser side javascript with an open source 3rd party library, or you can disable that and do it manually if you are still worried. The fact gmail never integrated PGP shows what a fraud google is.
alexis_fr 8y ago
Also, by guaranteeing we’re the source, it only makes us more liable for what is written. If I say something that reads like a commitment, or get upset, or tell a mistake, there’s always a chance of benefiting from a loophole during trial; if it was digitally signed, no escape. The best interest of companies and individuals is that others send them signed mail, and that they send non-signed mail... I think that doesn’t help at all. It’s different from signing a website, because one is way more self-conscious when putting informations on a website.
- pferde 8y ago
  Sorry, but that's nonsense. The Received headers in an e-mail can already guarantee that your company is the source.
writepub 8y ago
One reason is a trusted PKI. Even if an email is signed, how does one verify the ownership of the key? I hope certificate authorities aren't the answer here, we've all seen how that worked for the web. This is where a PKI on a blockchain makes sense. Product Pitch: Signed emails, with inbuilt verification of key ownership, backed by a PKI on the blockchain
- tpetry 8y ago
  Product Pitch: letsencrypt for s/mime, would solve soo many problems. Every mailing provider could acquire a certificate for you and automatically sign it without any user interaction.
- dcbadacd 8y ago
  Estonia provides everyone a smartcard with a per-person certificates on it, those could absolutely be used to exchange encrypted e-mails in general, but the reason they aren't is because e-mail clients do not support it, there isn't a single e-mail client that comes even remotely close to that functionality. People resort to encrypted containers ASICE and attach those.
mikekchar 8y ago
All I can say is OMG yes. I've been meaning to write the exact same blog post. How is it we're at 2019 and email clients don't demand some kind of signature? How is it that you can spoof email... simply by entering the fields however you want to? It's insane. I agree that the key exchange is difficult, but seriously I'll even take a CA if it means that I can reasonably tell that email that appears to come from my bank probably comes from my bank. Even better if a technical user can manage the keys themselves, but at least lets do the bare minimum!
- Arnt 8y ago
  PGP isn't demanded, but a different kind of signature is increasingly demanded: DKIM. Only a minority uses it to reject mail on its own (although I guess that minority is bigger than the number of PGP users), it's widely used as part of a scoring system.
- coldtea 8y ago
  >All I can say is OMG yes. I've been meaning to write the exact same blog post. How is it we're at 2019 and email clients don't demand some kind of signature? So that you have a false sense of security when the keys have been stolen from a clueless user you correspond with?
- cmroanirgo 8y ago
  For different people, there are different problems with email. For me, signing is less of an issue, but e2e privacy is: but so much meta data is leaked through headers that there's little point. Then there's the issue of web of trust which signing requires to be of use, which leaks (/publicises) email addresses in adding security. Its current implementation is utterly unusable for a-technical people (like my mum). For me, I'd prefer my server to be the arbitrator for signatures, which is a little like dkim anyway. Strong spf settings (-all rather than ~all) fixes a lot of spoofing like your bank example. It's a problem that I'd dearly loved to see fixed up though... but how? To move onto a better email system we need to keep everyone's use cases intact: some like pop, some imap, some would prefer direct messages instead. Personally, I'd like imap with a touch of direct messaging. So, how do you handle all the handshaking between 4 devices, while maintaining absolute privacy and assurances that nothing has been tampered, but nothing can be leaked? Hopefully better minds come up with a great solution, because all the ideas I've had are flawed in one way or another! (I've been thinking of writing an article on my thoughts...)
thunn 8y ago
I know this is just a spam email, but Queensland University of Technology (QUT) is different from University of Queensland. I hope you can adjust the names in your post! I have some University pride even if it is just spam
- iamben 8y ago
  It wasn't spam... That was the point of the article?
- Carpetsmoker 8y ago
  It wasn't spam; that was the point :-) I will adjust the name momentarily. Thanks for pointing it out.
deleted 8y ago
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jarjoura 8y ago
It’s easy. The mail teams at Apple, Google and Microsoft are running in maintenance mode and honestly there’s no money in it for them to invest in it.
- runn1ng 8y ago
  GMail just had a major redesign.
  - heavenlyblue 8y ago
    The literally only changed the CSS of the pages. Not even pagination logic was changed - what am I missing?
- olliej 8y ago
  Mail.app happily supports signing, and has done for like a decade - the problem is having some meaningful directory service. Basically, enterprises can often times set up internal key directories, but general publicly accessible directories are much more challenging (in a user friendly way). [edit to add instructions: 1. If you already have a public signature you can import it into keychain, otherwise create a certificate via Keychain Access | Certificate Assistant | Create a certificate... 2. set the permissions to allow it to be trusted for signing + decrypting email (in an enterprise environment this is automated) by double clicking the certificate in keychain access, expand /trust/ and set secure mail to "always trust". 3. In the subject field of a new mail you should now see a couple of buttons, the default (I think) is for signing to be enabled -- the right button ]
deleted 8y ago
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LoSboccacc 8y ago
Because it adds nothing. Unless both part exchange their keys securely and both parties store the keys securely you are just delegating identification to a different infrastructure with no indication of it being more secure but with an added false sense of security with is even more dangerous.
- ricardobeat 8y ago
  Yet this is exactly how SSL security is implemented. Speaking of that, couldn’t companies use their existing domain certificate to sign emails?
  - jcranmer 8y ago
    No. You need a CA certificate that is authorized to sign email certificates to sign the email certificate that signs emails. The domain certificate is merely authorized for the SSL connection itself, and the CA that signs it likely doesn't have trust bits for email either.
  - jhasse 8y ago
    You mean like DKIM? https://en.wikipedia.org/wiki/DomainKeys_Identified_Mail https://en.wikipedia.org/wiki/DomainKeys_Identified_Mail
- dijit 8y ago
  Either this is true and the CA system for HTTPS is (as you say) a false sense of security. Or it’s not true because we implicitly trust key signers; unless you’re talking about PGP only, which only has a web-of-trust model and a very poor usability track record. If that’s the case you should look at S/MIME which is very similar in its model to what we currently use for securing websites.
  - berbec 8y ago
    Well, the CA system for HTTPS is a false sense of Identity protection. Is great for encryption. 0: https://stripe.ian.sh/ https://stripe.ian.sh/
runn1ng 8y ago
Isn't this solved by DKIM, which at least GMail sort-of supports?
- cbg0 8y ago
  That only establishes that an e-mail sent from john@example.com was authorized for sending by example.com.
  - jhasse 8y ago
    And if example.com is a decent email provider, this also proves that it was sent by john, because otherwise the SMTP server wouldn't sign the outgoing email with a wrong login.
TomK32 8y ago
I do PGP sign my emails but not the mails that my little web app sends out. I should try that and see how users do react. How's the state at the receiving side? I mean what percentage of users would be displayed a message about the PGP signature being valid despite them neither using nor knowing about PGP?
- Carpetsmoker 8y ago
  I don't think there are many clients which support PGP out-of-the-box. The state of S/MIME is better though; I believe many desktop email clients already support it by default. Still, more work needs to be done. It's a bit of a catch-22: no one is signing their emails because client support isn't that good, and client support isn't improving because no one is signing emails.
e1ghtSpace 8y ago
Lol, Queensland University of Technology and The University of Queensland are two different universities.
dchest 8y ago
https://xkcd.com/1181/ https://xkcd.com/1181/
e1ghtSpace 8y ago
Weird, the email says Queensland University of Technology but the author talks about The University of Queensland. Two different universities but they are close (physically) to each other.
nicky0 8y ago
FWIW Facebook will not only sign but encrypt its emails sent to you using your PGP key.
hamilyon2 8y ago
Author does not mention dkim in article which makes me think he might not "read all the relevant RFCs" as he claims. Majority of important emails are signed and are not easy to spoof
- Carpetsmoker 8y ago
  I have updated the article to mention it: > DKIM is useful, but limited. All it does is verify that an email which claims to be from paypal.com is really from paypal.com. What it lacks is the ability to show warnings such as "this email wasn't signed, do you want to trust it?" and "this signature isn't recognized, yikes!" Perhaps such warnings could be accomplished with DKIM somehow (I'd have to study it to see), and if it can: great! But in its current state it's doing something different than what I'm proposing (which is why I omitted it originally).
  - jhasse 8y ago
    Well that UX somehow exists: If DKIM fails, the changes are high the email will be classified as spam or possible phishing.
- TobbenTM 8y ago
  I think the big issue is that not every email client reacts harshly enough to emails with either no DKIM header or mismatching DKIM signature. Today it's basically just one of several factors for marking a email as spam, when in reality it should show a big-ass red warning.
fooblat 8y ago
I used to work for a big tech company and the vast majority of people there signed all email by default and encrypted them when the content was sensitive. Part of onboarding was a training session on how all this works. Now I work for a non-tech startup and there are exactly two of us who sign our email. Happens to be another engineer I need to occasionally exchange encrypted messages with. As a positive, at least no one seems confused by my signed messages.
peteretep 8y ago
> Would probably have avoided Podesta and the entire Democratic Party a lot of trouble Unconvinced. The Podesta phishing email has: > From: Google <no-reply@accounts.googlemail.com> > Date: March 19, 2016 at 4:34:30 AM EDT > To: john.podesta@gmail.com > Subject: Sоmeоne has your passwоrd From a Google domain, to a Google domain. Google uses DKIM, so the sender, message-id, etc, WAS ALREADY SIGNED, and apparently got through anyway. Which part of this would further signing have helped?
no_gravity 8y ago
One reason is that SPF already accomplishes good enough sender identification without any hassle on the user side. When you get an email from joe@example.com and example.com is trustworthy and uses SPF, then you know that the sender in fact was joe@example.com It's easy enough to set up SPF for any domain. Gmail, Yahoo, Outlook etc all use it.
- dboreham 8y ago
  SPF is in general unusable because there are sufficient domains of sufficiently high value that don't have properly configured SPF records. Source: spent years maintaining a broken or missing SPF whitelist..
  - jhasse 8y ago
    I don't see how this would be different with PGP.
- Carpetsmoker 8y ago
  SPF can be a massive hassle since it's based on which server is sending emails, rather than which organisation is sending emails. Change some server and your SPF breaks. In a large organisations there can be a bunch of different ways of sending emails (main app uses SendGrid, marketing team uses SureyMonkey, some 3rdparty tool uses something else, etc.) In practice, I see administrators get SPF wrong all the time, which is why it's rare to see a hard-reject policy. In addition, the limitations of DKIM also apply to SPF: > DKIM is useful, but limited. All it does is verify that an email which claims to be from paypal.com is really from paypal.com. What it lacks is the ability to show warnings such as “this email wasn’t signed, do you want to trust it?” and “this signature isn’t recognized, yikes!”
  - deleted 8y ago
    [deleted]
  - jhasse 8y ago
    > What it lacks is the ability to show warnings such as “this email wasn’t signed, do you want to trust it?” and “this signature isn’t recognized, yikes!” Such a warning already exists: https://lifehacker.com/stop-looking-like-a-phisher-in-gmail-5875549 https://lifehacker.com/stop-looking-like-a-phisher-in-gmail-...
z3t4 8y ago
E-mail is transitioning to web based central/closed services. For example in Sweden - government do not send e-mail, instead they use a private proprietary service that require an Android or iPhone for second factor access, as an alternative to snail mail. So if you want to keep messaging decentralized, open and standardized, instead of just complaining, we need to try out things like e-mail signing. In order to improve we need to feel the pain points and engineer them away.
simias 8y ago
I always sign my email with PGP/MIME, although I do wonder if any of the recipients ever bothered to validate the signature. I mostly do it out of habit at this point. I use my GnuPG smartcard to authenticate through SSH and encrypt files so I might as well tell mutt to sign my email. These days I suspect that the average user simply trusts their provider's antispam to discard bogus emails (and as TFA points out, DKIM does effectively provide a signature, although obviously it's not the same trust model). I haven't given up on PGP, if anything I use it more than ever, but in this age of webmails and the general trend towards the centralization of the web I think the author is preaching in the desert.
- amelius 8y ago
  How do you distribute the public key?
  - simias 8y ago
    Through the usual keyserver network, keybase and my own web server.
kccqzy 8y ago
I was a period I actually sign every email I send. I stopped when I keep getting replies about there's this mysterious p7s attachment people can't open. And some people say their virus scanner thinks it's malware.
BlackLotus89 8y ago
At my current job it is "mandatory" to sign your mails with mime. We got the infrastructure in place. I have seen 3 signed mails up until now. A colleague of mine got the reply to one of his signed messages "can't read because it's encrypted". I would really love signed mails thought...
jcrites 8y ago
Email is already generally signed and verified when sent and received by competent email providers. DKIM and DMAC are the technologies that do this. DKIM employs asymmetric cryptography to sign all outbound emails from a domain name using a key for which the public part is published in the domain’s DNS. Receiving mail servers validate signatures automatically, looking up each domain’s public key from DNS. DMARC allows senders to advertise the fact that all email they send will be authenticated, such as with DKIM or SPF, so that receivers may drop anything else (kind of like HSTS for websites). Messages that lack a DKIM signature, from sending domains that require it, will simply be dropped. Quality email providers, including most webmail providers, offer these capabilities built in. These technologies are table stakes for email, like HTTPS is for websites. Take a look at received email in your mailbox for DKIM/DMARC status headers and you might find that many messages are protected by these technologies. However, even strong authentication of email addresses is not enough to prevent abuse. Attackers can send email from addresses that are similar (but not identical) to the person they want to impersonate (typo-similar domains). An attacker can fully set up the domain and employ DKIM+DMARC. Just like with TLS, possessing a key is not by itself an indicator of trustworthiness. Signing our email won’t stop people from being tricked by impersonators unfortunately. It’s similar to the phone system: if someone calls you and claims to be an employee of your bank, how do you know if it’s really them? The best answer is often to independently navigate to the bank’s website, look up their contact info, and then use it to reach them. The same is the for email addresses: you can’t assume that an address belongs to someone - you have to verify it somehow (using an existed trusted channel). Then DKIM+DMARC can help by making it impossible for anyone to forge messages from that address. A starting point for a better solution to the identity discovery problem could be a better address book experience, calling to the user’s attention the first time they’re communicating with a new person, especially at a new or different organization. Defending against phishing is more of a user experience design problem than a crypto engineering problem in my opinion.
- upofadown 8y ago
  DKIM and DMARC only verify the domain of the mail server ... which is something we care about only because the email clients can't do something better. A signed email identifies an individual sender. Pretty much apples and oranges.
upofadown 8y ago
A lot of the things people suggest as replacements for SMTP could be done with SMTP if email signing became standard. You could have closed message groups where you only have emails from people you have corresponded with before. So you could have a family INBOX, a company INBOX and a friends INBOX. Getting added to a particular INBOX would involve some communication out of band. This could be done in a very intuitive way. People would have no problem understanding the concept of a private INBOX. It would totally allow man in the middle attacks but spammers/scammers generally can not do such attacks and would not have any financial incentive anyway.
Labo333 8y ago
I think https://en.m.wikipedia.org/wiki/DMARC https://en.m.wikipedia.org/wiki/DMARC is meant for that. Of course it relies on trusted DNS.
pmontra 8y ago
The post is about signing, but the same applies to encryption: > "This is not comprehensible to the ordinary person." Too many moving parts, but there could be a solution. Unfortunately it's not going to happen. The solution is that the few big webmail providers start setting up end to end encryption using any open standard. It must be the same zero configuration stuff that worked for WhatsApp which every grandpa and grandma use. If they start doing it for messages sent between their addresses, the world will follow. Unfortunately this means that it must be done in the browser and the webmail provider can't see anything of the content. I don't think Google wants to see this happen even if they own the most used browser.
wtmt 8y ago
> For signing there’s more margin; it’s okay if half the people never verify your signatures. The problem that people may not verify signatures is one, but what's far worse is that bad email clients won't show the email content for emails signed with S/MIME certificates that have later expired. I was in an organization where S/MIME certificates were always issued with a validity of one year, and I used to sign all my mails. After a year, a colleague told me (and showed me) that my previous mails in Outlook couldn't be read any longer. Turns out that Outlook has a convoluted process to say "Yes, I know that the certificate used to sign this mail has now expired, but it was valid at the time of signing and I just want you to let me use it for older emails or just show me the email content with some warning". I had to go through a series of steps to make sure Outlook trusted those certificates for all mails. Email clients need to improve a lot more on usability if people are to use signatures and also manage multiple (expired) certificates.
mcculley 8y ago
I have been using S/MIME for over a decade. I used PGP a long time ago, but it was way too much to expect others to use. Now that S/MIME is built into major MUAs, it makes more sense. But one problem I have run into recently is that some correspondents complain that the attached smime.p7s file causes their system to mark my messages as spam. It has made me reconsider using it.
SamWhited 8y ago
I gave up on using PGP for personal communications ages ago (even ones where signing would actually be nice and not just a waste of time), but I still appreciate services that do this. For example, my repository hosting (sourcehut, https://git.sr.ht https://git.sr.ht) and related services sign emails. I could know nothing about their key, key management, levels of trust, etc. just that I hit trust the first time (I'm perfectly okay with a TOFU model here) and now I throw away any emails that don't have a green tick next to them in the "Signature" field. Email software could make this dead simple without requiring that the user know anything about the web of trust, regardless of how complicated PGP is under the hood. For most users, even webmail users, this would be good enough.
- rakoo 8y ago
  That is exactly what autocrypt (https://autocrypt.org/ https://autocrypt.org/) aims to do: define a protocol to effortlessly encrypt back and forth with no input from the user
cascom 8y ago
The only organizations that i see consistently signing their emails are the large commodity traders [1], not sure what drives it (third world country operations, secrecy, etc.) [1]https://en.wikipedia.org/wiki/List_of_commodity_traders#Modern_companies[3] https://en.wikipedia.org/wiki/List_of_commodity_traders#Mode...
MagicPropmaker 8y ago
At first thought, you'd think: All that would be needed to make this happen would be for gmail, outlook mail, and Apple's clients to support signed and/or encrypted mail and display a logo if the digital signature matches, say, a signature in your contacts. But spammers would probably just throw a "signed" or "verified" logo or text at the bottom of the mail and fool or confuse most people into trusting an email they shouldn't trust.
Proven 8y ago
Why bother? 1) It increases the cost of sending (especially "spam" aka official marketing and customer communications) 2) 99% of customers use either corporate or major email systems 3) 99% of customers have no clue what a "signed" email is (is that like when the sender inserts a PNG image of their scanned sig?) For 99% of practical purposes, it's isn't necessary or even desirable.
aidenn0 8y ago
It always surprised me that, back in the heydey of spam, few (if any) mailing lists required signatures for e-mails sent. Most of them were subscriber-only lists, and many were targeted at a highly technical audience, new subscribers were rare, and spam was not particularly targeted. I'm not sure how many person-hours per week was spent by moderators hand-filtering spam, and it definitely increased the delay for posts to appear. It doesn't make as much sense today with DKIM and friends, automated spam filtering, plus the general volume of spam is lower, but seemed like such a big win back then.
floatingatoll 8y ago
Because no mail client implements a sane process for acquiring and operating S/MIME certificates using an S/MIME-issuing CA within the mail client’s UX, much less doing so automatically for all configured email addresses using “confirmation link” emails occasionally.
joshfraser 8y ago
My company has been a frequent target of phishing attacks. Setting up the strictest possible SPF, DKIM and DMARC records and then reminding everyone to always verify the domain matches goes a really long way to keeping people safe. It might not be as perfect as end-to-end PGP, but it's available today & supported in almost all of the major email clients. If you haven't set up DMARC yet, it's a good place to start as it stops scammers from being able to spoof emails and make them look like they came from your domain.
- pard68 8y ago
  We, organization I work for, gave up on managing our own email. We pay Microsoft to do it. Their automated phishing detection is phenomenal. Maybe two or three emails slip through a quarter, down from dozens a month. We had so many because our user base gets an email address which expands the email base from employees to employees + customers, so 10k to 150k+ and once someone fell for the scam it would get resent from their address which looks much more convincing.
dcbadacd 8y ago
I wish Microsoft released the patents protecting SPFv2, it could help against quite a lot of spam but it can't be implemented by GPLv3 software, it's a pity.
mrgreenfur 8y ago
In lieu of signing, shouldn't links in emails be disabled wholesale at the enterprise/organization level? If we can't prove who it comes from, then you shouldn't click on it, end of story.
Zanni 8y ago
Okay, this may be off-topic, but I think the specific problem mentioned in the article would be much more easily solved by Queensland University of Technology providing context for the gift--which is already expected email etiquette. No need for a massive overhaul to email infrastructure. ("Off-topic" because the anecdote is a pretext for discussing signing email.) I once had a similar experience in real-life. I received a check via express mail with no accompanying letter or explanation, which seemed like it had to be bogus. Mindful of cashier check scams, I took it to my bank to see if it was safe to cash, and they erred on the side of caution and said, "no." But it was $600, so I cashed it anyway. And then about a month later, remembered I had closed out a poker account for that same amount. I'm all for security, but can we start with common courtesy?
spicytunacone 8y ago
I'm guilty of not signing my emails despite associating some accounts with my key. A fear I have is signing but the receiver, even someone in the general tech field, not understanding the surrounding text/attachments and dismissing my mail. I wonder if that's part of why these large orgs don't sign. I do agree with other comments that if big clients like Gmail abstracted PGP signing nicely for their users, it would put more pressure for organizations to publish public keys and sign lest the people they try to reach complain that Gmail gives them a nice big warning each time they try to open one of their emails.

270 points by Karrot_Kream 8y ago

I was so surprised when I received a signed email by Postfinance, my bank here in Switzerland. I really think it would be very beneficial if all major providers would start to use that. At first not many people would check the signature, but if then this takes momentum probably all major email provider will start to show an icon telling that the email is signed and verified. Just like Gmail shows when an email was received through a secure channel (TLS).

seanwilson 8y ago

I think if Gmail decided to implement email signing today as a prominent feature where they show a big warning for all non-signed emails the user demand for it would happen pretty quick e.g. WARNING: You cannot trust this email was sent from who it says it's from, the email have been modified in transit, and the email may have been read by hackers in transit Similar to how Chrome started showing non-HTTPS sites as "Not secure".

organsnyder 8y ago
They already show this information, but it's not prominent (I had to view the sender details to see it). https://support.google.com/mail/answer/6330403 https://support.google.com/mail/answer/6330403
- mankyd 8y ago
  Encryption and signing are different things here. Encryption in this case means that the contents of the email are encrypted between Google's servers and the recipient's servers. i.e. preventing snooping. Signing verifies that the contents of the email itself have been authenticated by the author. I.e. prevent spoofing.
  - organsnyder 8y ago
    Their documentation doesn't mention signing specifically, but wouldn't S/MIME include signing?
    - mankyd 8y ago
      Signing on behalf of the server, maybe, but gmail in no way supports/encourages having the actual author sign their messages, to my knowledge.

andrewstuart 8y ago

It's surprising to me that anyone could think that email signing was even vaguely in the ballpark of being comprehensible to the ordinary person.

droithomme 8y ago
It can be a pain even for the dedicated expert.
mikekchar 8y ago
Conceptually it's not hard at all. "When you send an email there is no proof that it came from you. It is easy to fake emails. When you press this button, it will 'digitally sign' the email. Now people can tell that it comes from you." It's the key exchange that's difficult. However, as the blog rightly points out, having companies sign their emails would be a massive step in the right direction. Every ordinary person uses an email service. If that email service handled the key exchange for those companies the it would be truly wonderful. It doesn't even need to be that difficult given that these companies almost certainly have certificates for their websites. Then all the service provider has to do is put this nice message when delivering the email: "This email was not signed by the company that it claims to be sent from. Beware." Not in any way difficult for an ordinary person to understand.
- duiker101 8y ago
  I think even conceptually it's hard. Your email address is your proof. You have to use a password to access it so it must mean only you can send emails with it.
  - stephenr 8y ago
    I can write your name as the sender on a physical letter and send it, and I can do the same thing with an email. There, conceptually it's explained, to anyone who has any concept of what "writing" is.
    - 8y ago

gudok 8y ago

Maybe it is because major email services already do good enough job of filtering spam/phishing emails? And yes, we already have DKIM.

Carpetsmoker 8y ago
(I am the author of this article, looks like someone posted it here before I got the chance) If they were, phishing would be a thing of the past; but it's not. In addition it's a lot harder to filter out targeted spear phishing with spam filters. Spam filtering is certainly useful – as are other measures such as the malicious website list that most browsers have – but it seems to me that adding extra guarantees such as signing would be a good thing? DKIM is useful, but also limited. It just detects forgeries of From address and such. Ideally email signing should be like https: if it's not https then you shouldn't trust it. DKIM can perhaps fill this role; but the current implementations don't; they just add some score to the spam-check.
- deleted 8y ago
  [deleted]
- evgen 8y ago
  You are begging the question by assuming that a signature on an email message proves anything useful to the recipient when the facts on the ground show this not to be the case. It is not harder to conduct phishing with email signatures, and the fact that such phishing campaigns have no problem putting TLS certs on their phishing sites is a simple existence proof of this fact. Email signatures does not impact spam in any significant manner beyond existing measures to prevent domain name forgery in the header. Spam email signed by joe@cheap-ray-bans.com does not stop being spam because it is signed and the signature provides no useful signal to spam filtering tools. The difference between an email signature and a TLS cert on a web site is that in the latter case the user is making an effort to connect to a specific site and the certificate ensures that they are in fact connecting to paypaaaaal.com even if other means were used to misdirect them to this site. With email there are two problems to be addressed, transport privacy/security (a sender problem) and unsolicited email (a recipient problem) and signatures are only useful in ensuring integrity of the former and do nothing for the latter.

deleted 8y ago

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elcomet 8y ago

Maybe one reason is because it is a hassle to check the signature of someone you didn't have already in your contact list ? How do you know it's not a fake signature ? Certainly you have to look at their website and find the key. But what if this person doesn't have a website ?

Tepix 8y ago
With S/MIME the certificate (signed by a known CA) is included in the email.
Carpetsmoker 8y ago
for S/MIME you don't need this; it's just a CA chain like HTTPS (for better or worse). For PGP I mentioned some possible options: > PGP could also be used; we can bypass much of the key exchange dilemma by just shipping email clients with keys for large organisations (PayPal, Google, etc.); like browsers do with some certificates. Or publish the keys on a DNS record. Even just publishing them on your website (or, if you’re a bank, in local branches etc.) so people can manually add them to their keyrings is a lot better than not signing anything at all!

mothsonasloth 8y ago

The average Joey Bloggs is just coming to terms with fake news and how to make their social media pages more private. PGP is not user friendly though and will never reach wide adoption until it's made easier or someone develops a service for it.

Carpetsmoker 8y ago
PGP doesn't need to be user-friendly just to verify signatures. It's like verifying your Linux distro's package system: all of them sign their packages (usually with PGP) and they get verified on installation, but as an end-user I never see it. And yes, PGP is hard, but only if I want to add signatures to my emails, or use it for encryption. But that's a different use case than what I wrote about here. I think this is exactly the sort of confusion I intended with: > Confusion between every-day “random person A emails random person B”-usage versus “large company with millions of users sends thousands of emails daily”-usage.
- BeetleB 8y ago
  >But that's a different use case than what I wrote about here. I find it amusing that the problem in the HN threads isn't that they know too little, it's that they know too much. They've seen arguments against PGP for years, and are having trouble processing the post in any way that is different from the "usual" PGP use cases they've seen. I'm seeing comments arguing that the user can't understand concepts of web of trust, or will get fooled by Paypals.com's signature, etc.
- deleted 8y ago
  [deleted]
ajcodez 8y ago
Isn’t that service Keybase?
- Leace 8y ago
  Keybase diverged so significantly from PGP that one wouldn't say "Keybase is PGP with good UX". You can say "Keybase is encryption with good UX" though.

z3t4 8y ago

There's nothing stopping spammers from signing their spam. The pain point with signing and encryption is key rotation. One problem is that both scammers and banks themselves use domains like paypal.accepournewtos.com or paypal.usersurvey.com and paypal@ourmailservice.randomdomain.com

Carpetsmoker 8y ago
> There's nothing stopping spammers from signing their spam. The pain point with signing and encryption is key rotation. Yes, but those signatures can't be verified. I understand this is tricky problem; how do we prevent people from simply clicking "accept this unknown key"? I'm not sure; but not every user is a blubbering idiot, and "unknown signature" strikes me as a lot better UX than "carefully look for spelling errors or misleading domain names".
- rebuilder 8y ago
  Why couldn't they get a certificate for accepourtos.com?
- chx 8y ago
  https://twitter.com/miradoreltd/status/843877685675868160 https://twitter.com/miradoreltd/status/843877685675868160 adopted from http://blog.johnath.com/images/snotweasel.png http://blog.johnath.com/images/snotweasel.png [Transcription: Windows XP error dialog with the yellow triangle - title "Something happened and you need to click OK to get on with things." details: "Certificate mismatch security identification administration communication intercept liliputian snotweasel foxtrot omegaforce." then you have a button saying Technical Crap and three radio buttons 1) More technical crap 2) Hoyvin-Glayvin 3) Launch photon torpedoes and then OK and Cancel buttons.]
  - riffraff 8y ago
    I will argue that something like the chrome untrusted certificate warning will scare away most of the users. https://i.stack.imgur.com/r0iOf.png https://i.stack.imgur.com/r0iOf.png

paxys 8y ago

Sure an email from Paypal.com can be signed or encrypted, but so can an identical one from Paypa1.com. How are users more protected in this case? In fact a big "sender verified" message in the email client for the latter email will cause a lot more phishing.

c256 8y ago
Web browsers already implement a ‘near miss that’s probably intentionally confusing” check on domains, and the code is readily extracted and shared (I know about it because someone extracted it and added it to Emacs a couple years ago). This seems like one of those cases where more large infrastructure people need to say “don’t let the perfect be the enemy of the good”.
- joombaga 8y ago
  > Web browsers already implement a ‘near miss that’s probably intentionally confusing” check on domains, What do they do with the information?
  - c256 8y ago
    For Emacs (and its web browsers, email clients, etc) this comes up in a concept of “confusables” strings that could easily be mistaken for other strings, usually as a result of Unicode tricks (multiple similar code points from different scripts, or composed versus combined characters, or sometimes ugly tricks with LtR/RtL markers. The code added to emacs was. A library that could be used to detect these probably-misleading tricks, but they didn’t implement a policy for them. The uses I saw of the library fell into the sort of “Danger, Will Robinson! This looks like it might be malicious” type warnings that can be found in most browsers these days.
pasta 8y ago
True, but two different issues. The domain part of signing is now being solved by DNS (PTR, SPF, Caller-ID). But signing still it has it's use because you also know the user exists. And encryption is very useful because most emails are stored as plain text on some server.

Tepix 8y ago

We need free S/MIME certificates with decent validity periods (remember, you have to keep around all certificates you've ever used!). Webmail (which a lot of people use) is also not ideal for dealing with certicates. You more or less have to trust the mail provider with your private keys. There are just countless attack vectors. Finally, it's quite technical to get a certificate, copy it to all your devices that have an email client and configure them.

Carpetsmoker 8y ago
I am not intimately familiar with the finances of PayPal, Google, Facebook, or Amazon.com, but I suspect they may be able to afford an S/MIME certificate. Perhaps even two or three! > Webmail (which a lot of people use) is also not ideal for dealing with certicates. You more or less have to trust the mail provider with your private keys. There are just countless attack vectors. You are already trusting the email provider with everything. What's so bad with trusting them to verify a signature, too? We're not communicating state secrets over encrypted email here; we're just verifying the signature on "PayPal sent you a message, click here to view it"-kind of emails.
- rebuilder 8y ago
  But the signature doesn't tell you the sender is the org they claim to be, because how would the verification system know who the sender says they are?
JorgeGT 8y ago
In my country anyone can get a free certificate from the Royal Mint. But few people uses them for email due to lack of support from webmail providers, as you say.
- rurounijones 8y ago
  Which country is this and do you have a link? sounds interesting.

emilsedgh 8y ago

I sign my emails with PGP all the time. One of the problems I noticed is that the signature ends up as an attachment and that confuses the hell out of many people. Did you send me an attachment? What was that file I couldn't open it!

p4bl0 8y ago
I do the same and I get that a lot. Most of the time from people using Outlook.
Carpetsmoker 8y ago
Once (or rather, if) PGP gains some traction this problem will disappear; email clients will improve the UX to show a specialised "PGP signed" box and hide the attachment.
- r_c_a_d 8y ago
  That's what I thought. But after 5 years I gave up and do not sign my emails any more.
- dredmorbius 8y ago
  It's been 23 years since MIME Security with Pretty Good Privacy (PGP) was proposed. http://www.faqs.org/rfcs/rfc2015.html http://www.faqs.org/rfcs/rfc2015.html I'm starting to think that someone really doesn't want this to happen.

edoo 8y ago

I always thought the best webmail would be one that uses PGP in purely browser side javascript with an open source 3rd party library, or you can disable that and do it manually if you are still worried. The fact gmail never integrated PGP shows what a fraud google is.

alexis_fr 8y ago

Also, by guaranteeing we’re the source, it only makes us more liable for what is written. If I say something that reads like a commitment, or get upset, or tell a mistake, there’s always a chance of benefiting from a loophole during trial; if it was digitally signed, no escape. The best interest of companies and individuals is that others send them signed mail, and that they send non-signed mail... I think that doesn’t help at all. It’s different from signing a website, because one is way more self-conscious when putting informations on a website.

pferde 8y ago
Sorry, but that's nonsense. The Received headers in an e-mail can already guarantee that your company is the source.

writepub 8y ago

One reason is a trusted PKI. Even if an email is signed, how does one verify the ownership of the key? I hope certificate authorities aren't the answer here, we've all seen how that worked for the web. This is where a PKI on a blockchain makes sense. Product Pitch: Signed emails, with inbuilt verification of key ownership, backed by a PKI on the blockchain

tpetry 8y ago
Product Pitch: letsencrypt for s/mime, would solve soo many problems. Every mailing provider could acquire a certificate for you and automatically sign it without any user interaction.
dcbadacd 8y ago
Estonia provides everyone a smartcard with a per-person certificates on it, those could absolutely be used to exchange encrypted e-mails in general, but the reason they aren't is because e-mail clients do not support it, there isn't a single e-mail client that comes even remotely close to that functionality. People resort to encrypted containers ASICE and attach those.

mikekchar 8y ago

All I can say is OMG yes. I've been meaning to write the exact same blog post. How is it we're at 2019 and email clients don't demand some kind of signature? How is it that you can spoof email... simply by entering the fields however you want to? It's insane. I agree that the key exchange is difficult, but seriously I'll even take a CA if it means that I can reasonably tell that email that appears to come from my bank probably comes from my bank. Even better if a technical user can manage the keys themselves, but at least lets do the bare minimum!

Arnt 8y ago
PGP isn't demanded, but a different kind of signature is increasingly demanded: DKIM. Only a minority uses it to reject mail on its own (although I guess that minority is bigger than the number of PGP users), it's widely used as part of a scoring system.
coldtea 8y ago
>All I can say is OMG yes. I've been meaning to write the exact same blog post. How is it we're at 2019 and email clients don't demand some kind of signature? So that you have a false sense of security when the keys have been stolen from a clueless user you correspond with?
cmroanirgo 8y ago
For different people, there are different problems with email. For me, signing is less of an issue, but e2e privacy is: but so much meta data is leaked through headers that there's little point. Then there's the issue of web of trust which signing requires to be of use, which leaks (/publicises) email addresses in adding security. Its current implementation is utterly unusable for a-technical people (like my mum). For me, I'd prefer my server to be the arbitrator for signatures, which is a little like dkim anyway. Strong spf settings (-all rather than ~all) fixes a lot of spoofing like your bank example. It's a problem that I'd dearly loved to see fixed up though... but how? To move onto a better email system we need to keep everyone's use cases intact: some like pop, some imap, some would prefer direct messages instead. Personally, I'd like imap with a touch of direct messaging. So, how do you handle all the handshaking between 4 devices, while maintaining absolute privacy and assurances that nothing has been tampered, but nothing can be leaked? Hopefully better minds come up with a great solution, because all the ideas I've had are flawed in one way or another! (I've been thinking of writing an article on my thoughts...)

thunn 8y ago

I know this is just a spam email, but Queensland University of Technology (QUT) is different from University of Queensland. I hope you can adjust the names in your post! I have some University pride even if it is just spam

iamben 8y ago
It wasn't spam... That was the point of the article?
Carpetsmoker 8y ago
It wasn't spam; that was the point :-) I will adjust the name momentarily. Thanks for pointing it out.

deleted 8y ago

[deleted]

jarjoura 8y ago

It’s easy. The mail teams at Apple, Google and Microsoft are running in maintenance mode and honestly there’s no money in it for them to invest in it.

runn1ng 8y ago
GMail just had a major redesign.
- heavenlyblue 8y ago
  The literally only changed the CSS of the pages. Not even pagination logic was changed - what am I missing?
olliej 8y ago
Mail.app happily supports signing, and has done for like a decade - the problem is having some meaningful directory service. Basically, enterprises can often times set up internal key directories, but general publicly accessible directories are much more challenging (in a user friendly way). [edit to add instructions: 1. If you already have a public signature you can import it into keychain, otherwise create a certificate via Keychain Access | Certificate Assistant | Create a certificate... 2. set the permissions to allow it to be trusted for signing + decrypting email (in an enterprise environment this is automated) by double clicking the certificate in keychain access, expand /trust/ and set secure mail to "always trust". 3. In the subject field of a new mail you should now see a couple of buttons, the default (I think) is for signing to be enabled -- the right button ]

deleted 8y ago

[deleted]

LoSboccacc 8y ago

Because it adds nothing. Unless both part exchange their keys securely and both parties store the keys securely you are just delegating identification to a different infrastructure with no indication of it being more secure but with an added false sense of security with is even more dangerous.

ricardobeat 8y ago
Yet this is exactly how SSL security is implemented. Speaking of that, couldn’t companies use their existing domain certificate to sign emails?
- jcranmer 8y ago
  No. You need a CA certificate that is authorized to sign email certificates to sign the email certificate that signs emails. The domain certificate is merely authorized for the SSL connection itself, and the CA that signs it likely doesn't have trust bits for email either.
- jhasse 8y ago
  You mean like DKIM? https://en.wikipedia.org/wiki/DomainKeys_Identified_Mail https://en.wikipedia.org/wiki/DomainKeys_Identified_Mail
dijit 8y ago
Either this is true and the CA system for HTTPS is (as you say) a false sense of security. Or it’s not true because we implicitly trust key signers; unless you’re talking about PGP only, which only has a web-of-trust model and a very poor usability track record. If that’s the case you should look at S/MIME which is very similar in its model to what we currently use for securing websites.
- berbec 8y ago
  Well, the CA system for HTTPS is a false sense of Identity protection. Is great for encryption. 0: https://stripe.ian.sh/ https://stripe.ian.sh/

runn1ng 8y ago

Isn't this solved by DKIM, which at least GMail sort-of supports?

cbg0 8y ago
That only establishes that an e-mail sent from john@example.com was authorized for sending by example.com.
- jhasse 8y ago
  And if example.com is a decent email provider, this also proves that it was sent by john, because otherwise the SMTP server wouldn't sign the outgoing email with a wrong login.

TomK32 8y ago

I do PGP sign my emails but not the mails that my little web app sends out. I should try that and see how users do react. How's the state at the receiving side? I mean what percentage of users would be displayed a message about the PGP signature being valid despite them neither using nor knowing about PGP?

Carpetsmoker 8y ago
I don't think there are many clients which support PGP out-of-the-box. The state of S/MIME is better though; I believe many desktop email clients already support it by default. Still, more work needs to be done. It's a bit of a catch-22: no one is signing their emails because client support isn't that good, and client support isn't improving because no one is signing emails.

e1ghtSpace 8y ago

Lol, Queensland University of Technology and The University of Queensland are two different universities.

dchest 8y ago

https://xkcd.com/1181/ https://xkcd.com/1181/

e1ghtSpace 8y ago

Weird, the email says Queensland University of Technology but the author talks about The University of Queensland. Two different universities but they are close (physically) to each other.

nicky0 8y ago

FWIW Facebook will not only sign but encrypt its emails sent to you using your PGP key.

hamilyon2 8y ago

Author does not mention dkim in article which makes me think he might not "read all the relevant RFCs" as he claims. Majority of important emails are signed and are not easy to spoof

Carpetsmoker 8y ago
I have updated the article to mention it: > DKIM is useful, but limited. All it does is verify that an email which claims to be from paypal.com is really from paypal.com. What it lacks is the ability to show warnings such as "this email wasn't signed, do you want to trust it?" and "this signature isn't recognized, yikes!" Perhaps such warnings could be accomplished with DKIM somehow (I'd have to study it to see), and if it can: great! But in its current state it's doing something different than what I'm proposing (which is why I omitted it originally).
- jhasse 8y ago
  Well that UX somehow exists: If DKIM fails, the changes are high the email will be classified as spam or possible phishing.
TobbenTM 8y ago
I think the big issue is that not every email client reacts harshly enough to emails with either no DKIM header or mismatching DKIM signature. Today it's basically just one of several factors for marking a email as spam, when in reality it should show a big-ass red warning.

fooblat 8y ago

I used to work for a big tech company and the vast majority of people there signed all email by default and encrypted them when the content was sensitive. Part of onboarding was a training session on how all this works. Now I work for a non-tech startup and there are exactly two of us who sign our email. Happens to be another engineer I need to occasionally exchange encrypted messages with. As a positive, at least no one seems confused by my signed messages.

peteretep 8y ago

> Would probably have avoided Podesta and the entire Democratic Party a lot of trouble Unconvinced. The Podesta phishing email has: > From: Google <no-reply@accounts.googlemail.com> > Date: March 19, 2016 at 4:34:30 AM EDT > To: john.podesta@gmail.com > Subject: Sоmeоne has your passwоrd From a Google domain, to a Google domain. Google uses DKIM, so the sender, message-id, etc, WAS ALREADY SIGNED, and apparently got through anyway. Which part of this would further signing have helped?

no_gravity 8y ago

One reason is that SPF already accomplishes good enough sender identification without any hassle on the user side. When you get an email from joe@example.com and example.com is trustworthy and uses SPF, then you know that the sender in fact was joe@example.com It's easy enough to set up SPF for any domain. Gmail, Yahoo, Outlook etc all use it.

dboreham 8y ago
SPF is in general unusable because there are sufficient domains of sufficiently high value that don't have properly configured SPF records. Source: spent years maintaining a broken or missing SPF whitelist..
- jhasse 8y ago
  I don't see how this would be different with PGP.
Carpetsmoker 8y ago
SPF can be a massive hassle since it's based on which server is sending emails, rather than which organisation is sending emails. Change some server and your SPF breaks. In a large organisations there can be a bunch of different ways of sending emails (main app uses SendGrid, marketing team uses SureyMonkey, some 3rdparty tool uses something else, etc.) In practice, I see administrators get SPF wrong all the time, which is why it's rare to see a hard-reject policy. In addition, the limitations of DKIM also apply to SPF: > DKIM is useful, but limited. All it does is verify that an email which claims to be from paypal.com is really from paypal.com. What it lacks is the ability to show warnings such as “this email wasn’t signed, do you want to trust it?” and “this signature isn’t recognized, yikes!”
- deleted 8y ago
  [deleted]
- jhasse 8y ago
  > What it lacks is the ability to show warnings such as “this email wasn’t signed, do you want to trust it?” and “this signature isn’t recognized, yikes!” Such a warning already exists: https://lifehacker.com/stop-looking-like-a-phisher-in-gmail-5875549 https://lifehacker.com/stop-looking-like-a-phisher-in-gmail-...

z3t4 8y ago

E-mail is transitioning to web based central/closed services. For example in Sweden - government do not send e-mail, instead they use a private proprietary service that require an Android or iPhone for second factor access, as an alternative to snail mail. So if you want to keep messaging decentralized, open and standardized, instead of just complaining, we need to try out things like e-mail signing. In order to improve we need to feel the pain points and engineer them away.

simias 8y ago

I always sign my email with PGP/MIME, although I do wonder if any of the recipients ever bothered to validate the signature. I mostly do it out of habit at this point. I use my GnuPG smartcard to authenticate through SSH and encrypt files so I might as well tell mutt to sign my email. These days I suspect that the average user simply trusts their provider's antispam to discard bogus emails (and as TFA points out, DKIM does effectively provide a signature, although obviously it's not the same trust model). I haven't given up on PGP, if anything I use it more than ever, but in this age of webmails and the general trend towards the centralization of the web I think the author is preaching in the desert.

amelius 8y ago
How do you distribute the public key?
- simias 8y ago
  Through the usual keyserver network, keybase and my own web server.

kccqzy 8y ago

I was a period I actually sign every email I send. I stopped when I keep getting replies about there's this mysterious p7s attachment people can't open. And some people say their virus scanner thinks it's malware.

BlackLotus89 8y ago

At my current job it is "mandatory" to sign your mails with mime. We got the infrastructure in place. I have seen 3 signed mails up until now. A colleague of mine got the reply to one of his signed messages "can't read because it's encrypted". I would really love signed mails thought...

jcrites 8y ago

Email is already generally signed and verified when sent and received by competent email providers. DKIM and DMAC are the technologies that do this. DKIM employs asymmetric cryptography to sign all outbound emails from a domain name using a key for which the public part is published in the domain’s DNS. Receiving mail servers validate signatures automatically, looking up each domain’s public key from DNS. DMARC allows senders to advertise the fact that all email they send will be authenticated, such as with DKIM or SPF, so that receivers may drop anything else (kind of like HSTS for websites). Messages that lack a DKIM signature, from sending domains that require it, will simply be dropped. Quality email providers, including most webmail providers, offer these capabilities built in. These technologies are table stakes for email, like HTTPS is for websites. Take a look at received email in your mailbox for DKIM/DMARC status headers and you might find that many messages are protected by these technologies. However, even strong authentication of email addresses is not enough to prevent abuse. Attackers can send email from addresses that are similar (but not identical) to the person they want to impersonate (typo-similar domains). An attacker can fully set up the domain and employ DKIM+DMARC. Just like with TLS, possessing a key is not by itself an indicator of trustworthiness. Signing our email won’t stop people from being tricked by impersonators unfortunately. It’s similar to the phone system: if someone calls you and claims to be an employee of your bank, how do you know if it’s really them? The best answer is often to independently navigate to the bank’s website, look up their contact info, and then use it to reach them. The same is the for email addresses: you can’t assume that an address belongs to someone - you have to verify it somehow (using an existed trusted channel). Then DKIM+DMARC can help by making it impossible for anyone to forge messages from that address. A starting point for a better solution to the identity discovery problem could be a better address book experience, calling to the user’s attention the first time they’re communicating with a new person, especially at a new or different organization. Defending against phishing is more of a user experience design problem than a crypto engineering problem in my opinion.

upofadown 8y ago
DKIM and DMARC only verify the domain of the mail server ... which is something we care about only because the email clients can't do something better. A signed email identifies an individual sender. Pretty much apples and oranges.

upofadown 8y ago

A lot of the things people suggest as replacements for SMTP could be done with SMTP if email signing became standard. You could have closed message groups where you only have emails from people you have corresponded with before. So you could have a family INBOX, a company INBOX and a friends INBOX. Getting added to a particular INBOX would involve some communication out of band. This could be done in a very intuitive way. People would have no problem understanding the concept of a private INBOX. It would totally allow man in the middle attacks but spammers/scammers generally can not do such attacks and would not have any financial incentive anyway.

Labo333 8y ago

I think https://en.m.wikipedia.org/wiki/DMARC https://en.m.wikipedia.org/wiki/DMARC is meant for that. Of course it relies on trusted DNS.

pmontra 8y ago

The post is about signing, but the same applies to encryption: > "This is not comprehensible to the ordinary person." Too many moving parts, but there could be a solution. Unfortunately it's not going to happen. The solution is that the few big webmail providers start setting up end to end encryption using any open standard. It must be the same zero configuration stuff that worked for WhatsApp which every grandpa and grandma use. If they start doing it for messages sent between their addresses, the world will follow. Unfortunately this means that it must be done in the browser and the webmail provider can't see anything of the content. I don't think Google wants to see this happen even if they own the most used browser.

wtmt 8y ago

> For signing there’s more margin; it’s okay if half the people never verify your signatures. The problem that people may not verify signatures is one, but what's far worse is that bad email clients won't show the email content for emails signed with S/MIME certificates that have later expired. I was in an organization where S/MIME certificates were always issued with a validity of one year, and I used to sign all my mails. After a year, a colleague told me (and showed me) that my previous mails in Outlook couldn't be read any longer. Turns out that Outlook has a convoluted process to say "Yes, I know that the certificate used to sign this mail has now expired, but it was valid at the time of signing and I just want you to let me use it for older emails or just show me the email content with some warning". I had to go through a series of steps to make sure Outlook trusted those certificates for all mails. Email clients need to improve a lot more on usability if people are to use signatures and also manage multiple (expired) certificates.

mcculley 8y ago

I have been using S/MIME for over a decade. I used PGP a long time ago, but it was way too much to expect others to use. Now that S/MIME is built into major MUAs, it makes more sense. But one problem I have run into recently is that some correspondents complain that the attached smime.p7s file causes their system to mark my messages as spam. It has made me reconsider using it.

SamWhited 8y ago

I gave up on using PGP for personal communications ages ago (even ones where signing would actually be nice and not just a waste of time), but I still appreciate services that do this. For example, my repository hosting (sourcehut, https://git.sr.ht https://git.sr.ht) and related services sign emails. I could know nothing about their key, key management, levels of trust, etc. just that I hit trust the first time (I'm perfectly okay with a TOFU model here) and now I throw away any emails that don't have a green tick next to them in the "Signature" field. Email software could make this dead simple without requiring that the user know anything about the web of trust, regardless of how complicated PGP is under the hood. For most users, even webmail users, this would be good enough.

rakoo 8y ago
That is exactly what autocrypt (https://autocrypt.org/ https://autocrypt.org/) aims to do: define a protocol to effortlessly encrypt back and forth with no input from the user

cascom 8y ago

The only organizations that i see consistently signing their emails are the large commodity traders [1], not sure what drives it (third world country operations, secrecy, etc.) [1]https://en.wikipedia.org/wiki/List_of_commodity_traders#Modern_companies[3] https://en.wikipedia.org/wiki/List_of_commodity_traders#Mode...

MagicPropmaker 8y ago

At first thought, you'd think: All that would be needed to make this happen would be for gmail, outlook mail, and Apple's clients to support signed and/or encrypted mail and display a logo if the digital signature matches, say, a signature in your contacts. But spammers would probably just throw a "signed" or "verified" logo or text at the bottom of the mail and fool or confuse most people into trusting an email they shouldn't trust.

Proven 8y ago

Why bother? 1) It increases the cost of sending (especially "spam" aka official marketing and customer communications) 2) 99% of customers use either corporate or major email systems 3) 99% of customers have no clue what a "signed" email is (is that like when the sender inserts a PNG image of their scanned sig?) For 99% of practical purposes, it's isn't necessary or even desirable.

aidenn0 8y ago

It always surprised me that, back in the heydey of spam, few (if any) mailing lists required signatures for e-mails sent. Most of them were subscriber-only lists, and many were targeted at a highly technical audience, new subscribers were rare, and spam was not particularly targeted. I'm not sure how many person-hours per week was spent by moderators hand-filtering spam, and it definitely increased the delay for posts to appear. It doesn't make as much sense today with DKIM and friends, automated spam filtering, plus the general volume of spam is lower, but seemed like such a big win back then.

floatingatoll 8y ago

Because no mail client implements a sane process for acquiring and operating S/MIME certificates using an S/MIME-issuing CA within the mail client’s UX, much less doing so automatically for all configured email addresses using “confirmation link” emails occasionally.

joshfraser 8y ago

My company has been a frequent target of phishing attacks. Setting up the strictest possible SPF, DKIM and DMARC records and then reminding everyone to always verify the domain matches goes a really long way to keeping people safe. It might not be as perfect as end-to-end PGP, but it's available today & supported in almost all of the major email clients. If you haven't set up DMARC yet, it's a good place to start as it stops scammers from being able to spoof emails and make them look like they came from your domain.

pard68 8y ago
We, organization I work for, gave up on managing our own email. We pay Microsoft to do it. Their automated phishing detection is phenomenal. Maybe two or three emails slip through a quarter, down from dozens a month. We had so many because our user base gets an email address which expands the email base from employees to employees + customers, so 10k to 150k+ and once someone fell for the scam it would get resent from their address which looks much more convincing.

dcbadacd 8y ago

I wish Microsoft released the patents protecting SPFv2, it could help against quite a lot of spam but it can't be implemented by GPLv3 software, it's a pity.

mrgreenfur 8y ago

In lieu of signing, shouldn't links in emails be disabled wholesale at the enterprise/organization level? If we can't prove who it comes from, then you shouldn't click on it, end of story.

Zanni 8y ago

Okay, this may be off-topic, but I think the specific problem mentioned in the article would be much more easily solved by Queensland University of Technology providing context for the gift--which is already expected email etiquette. No need for a massive overhaul to email infrastructure. ("Off-topic" because the anecdote is a pretext for discussing signing email.) I once had a similar experience in real-life. I received a check via express mail with no accompanying letter or explanation, which seemed like it had to be bogus. Mindful of cashier check scams, I took it to my bank to see if it was safe to cash, and they erred on the side of caution and said, "no." But it was $600, so I cashed it anyway. And then about a month later, remembered I had closed out a poker account for that same amount. I'm all for security, but can we start with common courtesy?

spicytunacone 8y ago

I'm guilty of not signing my emails despite associating some accounts with my key. A fear I have is signing but the receiver, even someone in the general tech field, not understanding the surrounding text/attachments and dismissing my mail. I wonder if that's part of why these large orgs don't sign. I do agree with other comments that if big clients like Gmail abstracted PGP signing nicely for their users, it would put more pressure for organizations to publish public keys and sign lest the people they try to reach complain that Gmail gives them a nice big warning each time they try to open one of their emails.