6 ms·

Midnight project: Password manager without a password manager

• rlpb 14y ago
  You receive an email from a sheepish website owner admitting that your password has been compromised and asking you to change it. Now what do you do?
  • e12e 14y ago
    Add a counter. For a nice discussion on a few of the tradeoffs involved in such a system as this, see this thread: http://www.mail-archive.com/cryptography@randombit.net/msg02875.html http://www.mail-archive.com/cryptography@randombit.net/msg02... So for this example, instead of: (sha512sum ~/.salt -<<<www.example.com;sha512sum -)|cut -d\ -f1|sha512sum|cut -c-32 eg: (sha512sum ~/.salt -<<<www.example.com0;sha512sum -)|cut -d\ -f1|sha512sum|cut -c-32 which can be changed to: (sha512sum ~/.salt -<<<www.example.com1;sha512sum -)|cut -d\ -f1|sha512sum|cut -c-32 You can "rediscover" the correct password for a site, relatively easy by using this method -- iterating up to your current (correct) password. Another alternative might be using the year or month/year of last password change/set... all these methods have drawbacks -- but again see the thread for some interesting points on a similar system. [edit: typo/formatting]
  • icebraining 14y ago
    Usually I just delete my account.
• jayfuerstenberg 14y ago
  This is fine for hackers but for mere mortals it looks cumbersome.
  • eps 14y ago
    Mortals simply use domainName+superSecretWord.
    • niemand 14y ago
      Shouldn't everyone know by now that this plain text concatenation scheme is insecure? By using this scheme, you're trusting $domainName to securely scramble the password. Once a single password is known in plain, an attacker has a nice password template that he can try on any site. The last few bits of security would be your user name (which is often similar to the one you use elsewhere) or nothing at all if you can log in by email address (which is usually possible these days; and that email address is often among the leaked information as well). Instant login anywhere! At least hash that '$domain+$masterpass' string... ----- More problems: I heard some people still truncate passwords down to unreasonable lengths on the server side, which might make hash compression (e.g. base 16 -> base 64) necessary and which will totally break the simple concatenation scheme, leaving a prefix of $domainName as the actual password. Ouch.
  • jroes 14y ago
    Yeah, I really like the idea, but there's no way I'm going to run all that stuff at the command line every time I need to generate a password. So, I wrote a gem: http://github.com/jroes/passwordy http://github.com/jroes/passwordy
• jhawthorn 14y ago
  Similar is https://www.pwdhash.com/ https://www.pwdhash.com/
  • aiiane 14y ago
    Also http://passwordmaker.org/ http://passwordmaker.org/
    • randomtyler 14y ago
      This /is/ PasswordMaker in infancy. I was a PasswordMaker user for a 3 or 4 years until the project stopped getting updates and they couldn't (or wouldn't) support Chrome.
      • kwanbis 14y ago
        There is PasswordMaker Pro on Chrome. I use it along PasswordMaker for Firefox and both generate the same password.
• StavrosK 14y ago
  This sounds similar to SuperGenPass, which I've used extensively since I heard about it.
• greenyoda 14y ago
  One major problem with this scheme is that if someone steals (or subpoenas) your computer they can discover all your passwords just by looking at your shell history. A password manager that's secured by a strong password doesn't have that vulnerability. Edit: As jroes pointed out below, this is not a problem.
  • jroes 14y ago
    They would only discover the domains, not the passwords you entered. You type the domain at the command line, but you type the password into stdin.
    • MTGandP 14y ago
      The program outputs your site-specific password to stdout. Is it possible for an attacker to get your stdout history?
      • lloeki 14y ago
        Might be. Some terminal emulators save logs. "Unlimited scrolling" often goes to disk, possibly in a file, possibly in swap (Terminal.app makes it stay in memory, which once consumed 3GB of RAM for my long-lived "rails server" tab). iTerm2 allows you to navigate back in time, while Terminal.app saves some data on quit to display on restore (if OSX autosave is enabled).
        • jaseg 14y ago
          When you allow less common tools to be used, one could use the bash or zsh read-builtin to read the master password without echoing (e.g. dash's read can not do that) and use xclip or similar to directly put the password into the X clipboard. With xclip's -l option you could even automagically "forget" the clipboard after it was pasted once.
• bigbird 14y ago
  Here's a little script that does something similar with some features that make it more useful (for hackers at any rate): https://github.com/jtmaher/Passwords https://github.com/jtmaher/Passwords
• antimora 14y ago
  This approach is cryptographically WEAKER than a password manager! Because password[0], password[1], ... password[n] are all related through common salt and master password string (and known domain name). Where as passwords stored in a password managers are independent. Therefore, in theory, if I know a few of your passwords (lets say I own 10 top domains and you've got accounts with me), I can crack your salt and password file, or at least, I can generate probable passwords for other domains.
  • cwp 14y ago
    Also, the advantage of not having to keep your password database secret is negated by problem of keeping your salt file secret.
    • gizzlon 14y ago
      Since when is your salt suppose to be secret?
      • pwg 14y ago
        >Since when is your salt suppose to be secret? In the instance of this particular algorithm, the salt must be kept secret, because it is the only unknown in the process from an attackers point of view.
        • gizzlon 14y ago
          Well, if that's true one should change the algorithm :)
        • icebraining 14y ago
          Not true, you have to input a master password (it's what the ';sha512sum -' part does), which is also unknown to the attacker.
          • pwg 14y ago
            Fair enough, but then the "salt" is not really a "salt" anymore as that term is known from "password salt", because it is no longer a random input value unique to each different password. It is simply a piece of known-plaintext input for every "hashing" session. That means that an attacker who can somehow obtain the salt value can now mount a known-plaintext attack against the outputs of the algorithm. http://en.wikipedia.org/wiki/Known-plaintext_attack http://en.wikipedia.org/wiki/Known-plaintext_attack I am ignoring the fact that in a general sense an attacker with resources to obtain the salt can also likely log the master password, in which case no attack against the algorithm is necessary.
• cypherpunks01 14y ago
  I trust Stanford PwdHash (https://www.pwdhash.com https://www.pwdhash.com) a lot more than this, and it basically does the same thing with some nice features and browser plugins.
• anon081312 14y ago
  I think this is catastrophically broken because of a known issue of how SHA-2 breaks its input into blocks: when A is aligned to a block boundary, sha(A || B) = f(sha(A), g(B)). http://en.wikipedia.org/wiki/Merkle%E2%80%93Damg%C3%A5rd_construction http://en.wikipedia.org/wiki/Merkle%E2%80%93Damg%C3%A5rd_con... In your system, the derived password is a sha digest of a concatentation of other sha digests. It almost has the form sha(sha(SALT) || sha(RESOURCE) || sha(MASTER)), with sha() returning the ascii encoding of the base-16 representation. (The difference is three extra newline characters "\n", which makes things slightly messier). This string representation for sha-512 digests is 128 characters or 1028 bits, and sha-512 uses 1028-bit input chunks, so the final sha() call reads the other three digests aligned on chunk boundaries. (Again, few bits off because of newlines, but this is not fatal). So DERIVED(RESOURCE) has a form DERIVED = sha(sha(SALT) || sha(RESOURCE) || sha(MASTER)) = f(sha(sha(SALT) || sha(RESOURCE)), g(sha(MASTER))) where f,g, are known functions. Moreover, f is reversible -- in SHA-512 it is just addition. So for an attack: given the salt, along with one resource/derived password pair, every other password can be computed. If you know SALT, RESOURCE_1, and DERIVED_1, you know these: sha(sha(SALT) || sha(RESOURCE_1)) DERIVED_1 = f(sha(sha(SALT) || sha(RESOURCE_1)), g(sha(MASTER))) Because f is reversible, and you know its first argument, you also learn its other argument, g(sha(MASTER)) and can calculate any other password, given the resource name. Note you don't learn the master password, nor its sha digest -- you can't reverse the block function g(), not without breaking SHA-2 itself. But that's not necessary.
  • dexen 14y ago
    > I think this is catastrophically broken because of a known issue of how SHA-2 breaks its input into blocks: when A is aligned to a block boundary, sha(A || B) = f(sha(A), g(B)). If that's the case, wouldn't it suffice to mix A and B, for example with byte-wise XOR? password ::= sha(A XOR B)
    • jaseg 14y ago
      Though that would be hard to do in a one-line shell script, which was the idea behind the gist.
  • 14y ago
• EGreg 14y ago
  We conceived of something like this for the web a couple years ago, as part of a much much larger picture: http://www.faqs.org/patents/app/20120110469#b http://www.faqs.org/patents/app/20120110469#b In our formulation, the salt was simply (a function of) your username. But yeah, we couldn't find a way to crack it, either.
  • pwg 14y ago
    > In our formulation, the salt was simply (a function of) your username. For password hashing, the input salt needs to be a cryptographically secure random number. This is because it needs to be unique, and unrelated, to each password. In your "formulation", what you have is simply a unique identifier for a user derived from the three, but it is in no way a "salt" as that term is used in regards to "salted passwords". > But yeah, we couldn't find a way to crack it, either. Just because you couldn't find a way to crack it, does not mean it is secure: http://security.stackexchange.com/questions/18197/why-shouldnt-we-roll-our-own http://security.stackexchange.com/questions/18197/why-should...
    • EGreg 14y ago
      on websites, usernames are unique, and they are usually unrelated to passwords on a related note, we encourage each of our users to select a passphrase, and even scour yahoo news from the past year, and other sources for three consecutive words, that the user can easily remember, such as "that truck driver" or "what he did". This in practice causes users to have a much better space of possible passwords to begin with ... without which any system would be susceptible to brute force rainbow table type attacks.
      • pwg 14y ago
        >encourage each of our users to select a passphrase, and even scour yahoo news from the past year, and other sources for three consecutive words, that the user can easily remember, such as "that truck driver" or "what he did". This in practice causes users to have a much better space of possible passwords to begin with And with a wordlist of the 10,000 most common words, if you are not also using a key-stretch function (bcrypt, pbkdf2, etc.) all of those examples become quite trivial to a john-the-ripper ( http://www.openwall.com/john/ http://www.openwall.com/john/ ) type attack. I.e., a three word phrase consisting of one each of the 10,000 most common words has at most 10000^3 combinations (1e+12). A 10 digit random password selected from letters, numbers, punctuation (94 digits) has 94^10 combinations (5e+19). 5e+19 is significantly larger than 1e+12)