7 ms·

Privacy, Security and Your Dropbox

67 points by AndrewDucker 16y ago

AndrewDucker 16y ago
Personally, I can't see that they can do much more than this. If they're going to supply access via the website, or allow you to share with others then they need to be able to decrypt the file. I never assumed that it was impossible for them to get access to my files. I just assumed that only certain people had access to the keys, and they only gave them out to third parties when forced to by law.
- thaumaturgy 16y ago
  I think that part of what's going on is that savvy users have become wary of trusting companies to securely manage their data. I first started reading Slashdot shortly after they launched; that was almost 15 years ago. It wasn't long after their launch that they started running articles on technology companies doing bad or stupid things with users' data, and there have been so many examples on so many forums in the intervening years that, to be honest, I'm literally disgusted every time another one comes around. Trusting companies to, for example, only give access to our data when forced to by law just doesn't cut it anymore, for a lot of people. Not when companies collectively have a very poor track record in this regard, and not when the law continues to be murky and dynamic (and abused). It's the abused dog effect: even if you, personally, treat a previously abused dog really well and swear up and down that you will never hurt it, if you raise your hand around it, it'll cower. Since technical solutions exist for this problem, Dropbox's reasoning gets a bit thinner. > If they're going to supply access via the website, or allow you to share with others then they need to be able to decrypt the file. Not necessarily. For example, a key derivation function could be used to transform a password into a key, and that password could be required for users that want that kind of thing. As far as website access goes, I'm about to commit a terrible security crime here and suggest that the key derivation function could also be run in the browser. This would prevent direct access to your data by anybody at Dropbox, at least until the next time you log in, at which point they could serve up some malicious code that would record your password and ship it off to them. There are workarounds for that, too, though.
- kragen 16y ago
  > If they're going to supply access via the website, or allow you to share with others then they need to be able to decrypt the file. They need to be able to decrypt the file right then to give you access via the website. They don't need to be able to decrypt the file the rest of the time. If the encryption key depends on your password, this is easy to implement. In modern browsers, this could actually be done in the browser, so that the keys for decrypting the file never reach their servers. To allow you to share individual files with others, they could encrypt each file with a randomly-generated session key, which is encrypted with your user key. When you give access to the file to a recipient, you would be encrypting a copy of that session key with the recipient's public key. In actual fact, it appears that anyone who knows the secure hash of the file's content is able to discover that Dropbox is storing it: http://paranoia.dubfire.net/2011/04/how-dropbox-sacrifices-user-privacy-for.html http://paranoia.dubfire.net/2011/04/how-dropbox-sacrifices-u... — and there's at least well-founded speculation, if not proof, that this means that knowing the secure hash is sufficient to read the file: http://news.ycombinator.com/item?id=2440074 http://news.ycombinator.com/item?id=2440074 For their previous statements to be true — that their employees have no access to your files — they would have to be doing something like this.
  - AndrewDucker 16y ago
    Making it password dependent means that they have to decrypt/encrypt when you change password. And also that you losing your password is apocalyptically bad.
    - kragen 16y ago
      There are some ways around that, but basically you're correct. (For example, you could store the user key, or an additional randomly-generated password, persistently on client machines, so that you can usually recover from password loss; and you could use a tree of session keys to minimize the amount you have to re-encrypt. But basically you're right.) It's understandable that they chose a less-secure system design. It's not understandable that they chose to lie to their customers about it.
      - 16y ago
muppetman 16y ago
I love that they openly in this post discuss that the end-user can use TrueCrypt if they desire: "For users who feel more comfortable managing their own encryption keys, we recommend using products like TrueCrypt to store encrypted volumes within their Dropboxes. Those users will unfortunately lose access to some functionality, but we leave this decision to the user." It's the sign of a good company in my opinion that they don't treat their users as unable to understand such things.
- pieter 16y ago
  Except that when you use TrueCrypt most of the functionality of DropBox stops working; you can't access your files through the web interface anymore (duh), but most importantly, you can't use the volume on two machines at the same time.
  - king_jester 16y ago
    I've used TrueCrypt volumes with Dropbox before, and when I encountered a situation where I wanted to access the volume from two places, I took the sensitive data from Dropbox and just exposed it on my private network where I have more control over access. As far as I can tell, there isn't a great way to keep high security and flexibility when using sensitive data with Dropbox, but keeping sensitive data on the cloud is always a risky affair anyway.
kragen 16y ago
These are weasel words. Miguel de Icaza's post explains the issue: > My problem is that for as long as I have tried to figure out, Dropbox made some bold claims about how your files were encrypted and how nobody had access to them, with statements like:… > - Dropbox employees aren't able to access user files, and when troubleshooting an account they only have access to file metadata (filenames, file sizes, etc., not the file contents)… > But this announcement that they are able to decrypt the files on behalf of the government contradicts their prior public statements. Dropbox are avoiding answering this. If they derived the encryption key from your password, as JWZ explained http://www.jwz.org/blog/2011/04/dropbox-doesnt-actually-encrypt-your-files/ http://www.jwz.org/blog/2011/04/dropbox-doesnt-actually-encr... and as occurred to any halfway decent hacker, they wouldn't need to have the ability for their employees to decrypt your files — an ability which they are still claiming to not have. And this is just insulting: > We understand that many of you have been confused by this situation — and some folks even felt like we misled them The problem isn't that we were confused or what we felt or that we were unintentionally "misled". The problem is that, apparently, you lied to us in order to defraud your customers.
- blub 16y ago
  I don't think they've lied, I've always known about the fact that they manage the encryption keys, it was one of the first things I looked for when the service was launched.
- palish 16y ago
  You still haven't explained what it is you expect them to do. In reality. Knowing that they have millions of customers, and that they have invested years of work into their current infrastructure. So, playing devil's advocate for the moment --- and taking the above facts into account --- what, precisely, would you do in their position?
  - blub 16y ago
    JungleDisk uses an encryption key protected by an additional password. To access your files online you have to provide this additional password which is used to decrypt the encryption key for the actual data. Granted, they can still steal your password...
16s 16y ago
This sounds as if they are doing users a favor: We manage the encryption keys on our users’ behalf. To be completely clear to users, they should instead write: We hold the decryption keys and can decrypt your data if compelled to do so. If you don't want us to be able to decrypt your data, encrypt it yourself with GPG or OpenSSL before sending your data to our site. Edit: Spelling & clarity.
- palish 16y ago
  They said almost exactly that. "If you want to be completely secure, use a program such as TrueCrypt to create an encrypted drive within your Dropbox."
- brk 16y ago
  No, they shouldn't write that. Dropbox is a consumer file storage company. Statements like that will confuse the majority of their target market and stall adoption of the service. What Dropbox is doing in relation to security/encryption is about the best possible solution that balances features and function with data protection for files that might be leaked or stolen. If you have suggestions for Dropbox, lay out concise technical suggestions. Writing new legalese for them is not solving any of the problems that people are getting so worked up about.
  - extension 16y ago
    Either way, those users will not understand the security of the service they are using. At least with the long version, they'll be aware of their lack of understaning.
deleted 16y ago
[deleted]
sunchild 16y ago
This isn't legal advice, but this seems to meet the same legal requirements that big companies must adhere to when using outsourcing providers that will have access to sensitive client data. The magic words: "Like most major online services, we have a small number of employees who must be able to access user data when legally required to do so. But that’s the exception, not the rule. We have strict policy and technical access controls that prohibit employee access except in these rare circumstances. In addition, we employ a number of physical and electronic security measures to protect user information from unauthorized access."
- bxr 16y ago
  Its not about the fact that they comply with court orders, of course they're going to, it is in their ability to give the courts unencrypted data that they shed light on the real issue to do something they said was impossible. If it were impossible for them to get at the unencrypted data, the encrypted data would be all that that had to had over.
roblund 16y ago
I actually really like that they did a point by point response to their critics. To me this is an important step for today's companies. The internet gives a voice to customers to raise concerns, companies are able to see these concerns immediately, and companies have a great way to respond quickly. I feel like it this type of dialog creates a win-win situation for everybody involved.
Enlightenment 16y ago
#1 - Use WinZip or WinRar or favorite archiver or encrypting tools to create an encrypted file. #2 - Copy encrypted file to DropBox folder. #3 - Done.
nathanb 16y ago
Holy cow, one request per month is low? I know that's less than one account in a million, but that's still way higher than I expected.
wewyor 16y ago
If anyone wants to vote for a feature of client side encryption there is a votebox here: https://www.dropbox.com/votebox/21/client-side-encryption https://www.dropbox.com/votebox/21/client-side-encryption
deleted 16y ago
[deleted]
ganis 16y ago
I think it's impossible to have deduplication (a system to prevent duplication) in encrypted data with different key for each user (the same file from different user will be encrypted differently) without dropbox storing the key (to decrypt back). Which means they have access to the files. We should know this from the very beginning. If it wasn't, how to check the files for deduplication? Enlighten me please.
canderson 16y ago
If Dropbox has one key per user, then how do they do deduplication? We know they do deduplication (http://tinyurl.com/4276pxu http://tinyurl.com/4276pxu) so this suggests a very small number of keys.
- sorbus 16y ago
  Storing unencrypted file hashes is the easiest way I can see to do it; then, for deduplication, the file is decrypted using one user's key, and a copy is made and encrypted under the second user's key.

67 points by AndrewDucker 16y ago

Personally, I can't see that they can do much more than this. If they're going to supply access via the website, or allow you to share with others then they need to be able to decrypt the file. I never assumed that it was impossible for them to get access to my files. I just assumed that only certain people had access to the keys, and they only gave them out to third parties when forced to by law.

thaumaturgy 16y ago
I think that part of what's going on is that savvy users have become wary of trusting companies to securely manage their data. I first started reading Slashdot shortly after they launched; that was almost 15 years ago. It wasn't long after their launch that they started running articles on technology companies doing bad or stupid things with users' data, and there have been so many examples on so many forums in the intervening years that, to be honest, I'm literally disgusted every time another one comes around. Trusting companies to, for example, only give access to our data when forced to by law just doesn't cut it anymore, for a lot of people. Not when companies collectively have a very poor track record in this regard, and not when the law continues to be murky and dynamic (and abused). It's the abused dog effect: even if you, personally, treat a previously abused dog really well and swear up and down that you will never hurt it, if you raise your hand around it, it'll cower. Since technical solutions exist for this problem, Dropbox's reasoning gets a bit thinner. > If they're going to supply access via the website, or allow you to share with others then they need to be able to decrypt the file. Not necessarily. For example, a key derivation function could be used to transform a password into a key, and that password could be required for users that want that kind of thing. As far as website access goes, I'm about to commit a terrible security crime here and suggest that the key derivation function could also be run in the browser. This would prevent direct access to your data by anybody at Dropbox, at least until the next time you log in, at which point they could serve up some malicious code that would record your password and ship it off to them. There are workarounds for that, too, though.
kragen 16y ago
> If they're going to supply access via the website, or allow you to share with others then they need to be able to decrypt the file. They need to be able to decrypt the file right then to give you access via the website. They don't need to be able to decrypt the file the rest of the time. If the encryption key depends on your password, this is easy to implement. In modern browsers, this could actually be done in the browser, so that the keys for decrypting the file never reach their servers. To allow you to share individual files with others, they could encrypt each file with a randomly-generated session key, which is encrypted with your user key. When you give access to the file to a recipient, you would be encrypting a copy of that session key with the recipient's public key. In actual fact, it appears that anyone who knows the secure hash of the file's content is able to discover that Dropbox is storing it: http://paranoia.dubfire.net/2011/04/how-dropbox-sacrifices-user-privacy-for.html http://paranoia.dubfire.net/2011/04/how-dropbox-sacrifices-u... — and there's at least well-founded speculation, if not proof, that this means that knowing the secure hash is sufficient to read the file: http://news.ycombinator.com/item?id=2440074 http://news.ycombinator.com/item?id=2440074 For their previous statements to be true — that their employees have no access to your files — they would have to be doing something like this.
- AndrewDucker 16y ago
  Making it password dependent means that they have to decrypt/encrypt when you change password. And also that you losing your password is apocalyptically bad.
  - kragen 16y ago
    There are some ways around that, but basically you're correct. (For example, you could store the user key, or an additional randomly-generated password, persistently on client machines, so that you can usually recover from password loss; and you could use a tree of session keys to minimize the amount you have to re-encrypt. But basically you're right.) It's understandable that they chose a less-secure system design. It's not understandable that they chose to lie to their customers about it.
    - 16y ago

muppetman 16y ago

I love that they openly in this post discuss that the end-user can use TrueCrypt if they desire: "For users who feel more comfortable managing their own encryption keys, we recommend using products like TrueCrypt to store encrypted volumes within their Dropboxes. Those users will unfortunately lose access to some functionality, but we leave this decision to the user." It's the sign of a good company in my opinion that they don't treat their users as unable to understand such things.

pieter 16y ago
Except that when you use TrueCrypt most of the functionality of DropBox stops working; you can't access your files through the web interface anymore (duh), but most importantly, you can't use the volume on two machines at the same time.
- king_jester 16y ago
  I've used TrueCrypt volumes with Dropbox before, and when I encountered a situation where I wanted to access the volume from two places, I took the sensitive data from Dropbox and just exposed it on my private network where I have more control over access. As far as I can tell, there isn't a great way to keep high security and flexibility when using sensitive data with Dropbox, but keeping sensitive data on the cloud is always a risky affair anyway.

kragen 16y ago

These are weasel words. Miguel de Icaza's post explains the issue: > My problem is that for as long as I have tried to figure out, Dropbox made some bold claims about how your files were encrypted and how nobody had access to them, with statements like:… > - Dropbox employees aren't able to access user files, and when troubleshooting an account they only have access to file metadata (filenames, file sizes, etc., not the file contents)… > But this announcement that they are able to decrypt the files on behalf of the government contradicts their prior public statements. Dropbox are avoiding answering this. If they derived the encryption key from your password, as JWZ explained http://www.jwz.org/blog/2011/04/dropbox-doesnt-actually-encrypt-your-files/ http://www.jwz.org/blog/2011/04/dropbox-doesnt-actually-encr... and as occurred to any halfway decent hacker, they wouldn't need to have the ability for their employees to decrypt your files — an ability which they are still claiming to not have. And this is just insulting: > We understand that many of you have been confused by this situation — and some folks even felt like we misled them The problem isn't that we were confused or what we felt or that we were unintentionally "misled". The problem is that, apparently, you lied to us in order to defraud your customers.

blub 16y ago
I don't think they've lied, I've always known about the fact that they manage the encryption keys, it was one of the first things I looked for when the service was launched.
palish 16y ago
You still haven't explained what it is you expect them to do. In reality. Knowing that they have millions of customers, and that they have invested years of work into their current infrastructure. So, playing devil's advocate for the moment --- and taking the above facts into account --- what, precisely, would you do in their position?
- blub 16y ago
  JungleDisk uses an encryption key protected by an additional password. To access your files online you have to provide this additional password which is used to decrypt the encryption key for the actual data. Granted, they can still steal your password...

16s 16y ago

This sounds as if they are doing users a favor: We manage the encryption keys on our users’ behalf. To be completely clear to users, they should instead write: We hold the decryption keys and can decrypt your data if compelled to do so. If you don't want us to be able to decrypt your data, encrypt it yourself with GPG or OpenSSL before sending your data to our site. Edit: Spelling & clarity.

palish 16y ago
They said almost exactly that. "If you want to be completely secure, use a program such as TrueCrypt to create an encrypted drive within your Dropbox."
brk 16y ago
No, they shouldn't write that. Dropbox is a consumer file storage company. Statements like that will confuse the majority of their target market and stall adoption of the service. What Dropbox is doing in relation to security/encryption is about the best possible solution that balances features and function with data protection for files that might be leaked or stolen. If you have suggestions for Dropbox, lay out concise technical suggestions. Writing new legalese for them is not solving any of the problems that people are getting so worked up about.
- extension 16y ago
  Either way, those users will not understand the security of the service they are using. At least with the long version, they'll be aware of their lack of understaning.

deleted 16y ago

[deleted]

sunchild 16y ago

This isn't legal advice, but this seems to meet the same legal requirements that big companies must adhere to when using outsourcing providers that will have access to sensitive client data. The magic words: "Like most major online services, we have a small number of employees who must be able to access user data when legally required to do so. But that’s the exception, not the rule. We have strict policy and technical access controls that prohibit employee access except in these rare circumstances. In addition, we employ a number of physical and electronic security measures to protect user information from unauthorized access."

bxr 16y ago
Its not about the fact that they comply with court orders, of course they're going to, it is in their ability to give the courts unencrypted data that they shed light on the real issue to do something they said was impossible. If it were impossible for them to get at the unencrypted data, the encrypted data would be all that that had to had over.

roblund 16y ago

I actually really like that they did a point by point response to their critics. To me this is an important step for today's companies. The internet gives a voice to customers to raise concerns, companies are able to see these concerns immediately, and companies have a great way to respond quickly. I feel like it this type of dialog creates a win-win situation for everybody involved.

Enlightenment 16y ago

#1 - Use WinZip or WinRar or favorite archiver or encrypting tools to create an encrypted file. #2 - Copy encrypted file to DropBox folder. #3 - Done.

nathanb 16y ago

Holy cow, one request per month is low? I know that's less than one account in a million, but that's still way higher than I expected.

wewyor 16y ago

If anyone wants to vote for a feature of client side encryption there is a votebox here: https://www.dropbox.com/votebox/21/client-side-encryption https://www.dropbox.com/votebox/21/client-side-encryption

deleted 16y ago

[deleted]

ganis 16y ago

I think it's impossible to have deduplication (a system to prevent duplication) in encrypted data with different key for each user (the same file from different user will be encrypted differently) without dropbox storing the key (to decrypt back). Which means they have access to the files. We should know this from the very beginning. If it wasn't, how to check the files for deduplication? Enlighten me please.

canderson 16y ago

If Dropbox has one key per user, then how do they do deduplication? We know they do deduplication (http://tinyurl.com/4276pxu http://tinyurl.com/4276pxu) so this suggests a very small number of keys.

sorbus 16y ago
Storing unencrypted file hashes is the easiest way I can see to do it; then, for deduplication, the file is decrypted using one user's key, and a copy is made and encrypted under the second user's key.