6 ms·

A basic salted hash would prevent this sort of thing (not saying that bcrypt/etc. aren't worth using). As to people using obvious password hints, it depends ho

• aw3c2 13y ago
  A basic salt could be just a fixed string being used. That would not prevent this. The salt would need to vary per hash.
  • eCa 13y ago
    The obvious solution is to salt it with something that is unique to that account: The internal account id, a string randomized at account creation or something like that. An identical password for two different accounts should never encrypt to the same string.
    • hag 13y ago
      The salt should always be random. If it's based on some account information it's possible that the salt can be regenerated if that account information would become available, in a DB dump like this for example.
      • eCa 13y ago
        If they had used different salts for every account, and that salt was published in this dump it would have been much more difficult to find identical passwords compared to the current situation. I'm not sure how you can keep the salt random and secret, and still use it when users log in?
        • sillysaurus2 13y ago
          Salts aren't secret. The point of salting a password is to prevent the password (like "alskdjfalsdf") from always hashing to the same result (like "j9p+HwtWWT86aMjgZFLzYg=="). That prevents rainbow table attacks (among others) and it doesn't require the salt be secret.
          • jsmeaton 13y ago
            Right. But the parent comment was replying to a comment suggesting that a user id (or other account information) shouldn't be used as it's not random. I can't see why a user id could not be used as a salt though.
            • justincormack 13y ago
              "I can't see why a user id could not be used as a salt though" thats exactly how people break crypto implementations, it seems ok but you dont really know. Don't just invent your own way, use the standard one.
            • cbr 13y ago
              If lots of sites all use user ids as a salt and all count up from 1 then a much weaker version of this attack applies: you can identify all the people who have both the same password and the same user id. If this were common, someone constructing a lookup table for password hashes could include ones salted with the first N user ids. A N-times bigger table isn't something you'd be excited about as a cracker, but might still be practical. If your user ids are randomly assigned this should be pretty much the same as generating a random salt. Still, the extra storage of a salt is going to be small compared to whatever else you're storing per-user, so better to do the safe thing and go with what's standard.
        • plywoodtrees 13y ago
          The salt is typically stored in the password db, alongside the salted hash. If Adobe has taken that approach, the intruders would have all the salts, but they would not be able to do this attack of seeing how many people use the same password. However, Snowden's silly password hint would still have given the game away. If that is in fact him.
      • raverbashing 13y ago
        Yes, it should be random but the salt is public information. Exactly because you need it to calculate the hash and compare it.
      • mcv 13y ago
        If it's random, you need to store it, and it becomes just as available on a leak. The salt still works though, because it makes all hashes different. You need to attack each password individually rather than tackling them all with a rainbow table or something. The approach from this article also stops working. What you use as a salt is fairly irrelevant as far as I can tell. If you want to get more security on top of that out of your salt, the only thing I can think is to add some security by obscurity on top: If it doesn't matter which field in the DB you use, just pick an unlikely one and keep secret which one it is. Might be id, email, favourite pet, or something else. Just don't forget to update the hash when the user changes that field.
  • judofyr 13y ago
    This is a common misconception, but a "global salt" isn't actually a salt. Not sure what a "basic salt" is though. > A new salt is randomly generated for each password. In a typical setting, the salt and the password are concatenated and processed with a cryptographic hash function, and the resulting output (but not the original password) is stored with the salt in a database. http://en.wikipedia.org/wiki/Salt_%28cryptography%29 http://en.wikipedia.org/wiki/Salt_%28cryptography%29
    • aw3c2 13y ago
      Ah, I did not know that. And I wrote some password hashing with a global salt myself. So I stand by my comment with "one laughing and one crying eye". I thought salts were mostly against precomputed rainbow tables for specific hash functions, but of course if my hashes are valuable enough, a global salt makes cracking them easier than if I used a random/unique one per hash.
      • sillysaurus2 13y ago
        This is why programmers should stop trying to write their own password systems.
        • amenod 13y ago
          To be exact, programmers should stop using their own password systems (unless - well, let's not go there :). Writing them is actually an excellent exercise, and humbling one too. Especially if you show your code to some skilled hacker / security expert.
      • jtheory 13y ago
        From what I understand rainbow tables are not really used anymore -- they were useful when it took longer to calculate hashes, but nowadays you just need a decent graphics card to calculate a few billion hashes (MD5 or SHA1) PER SECOND. Per-hash salts don't really slow that down at all, unfortunately. Short-version: don't use the hash algorithms that are designed to be fast for protecting sensitive data; use something solid with a work factor instead.
• kevjiang 13y ago
  Amazingly, these aren't even password hashes.. they're encrypted versions of the password. Ars wrote an article on this yesterday [1]. Basically if anyone has the encryption key, they'd be able to decrypt ALL passwords in the list. [1] http://arstechnica.com/security/2013/11/how-an-epic-blunder-by-adobe-could-strengthen-hand-of-password-crackers/ http://arstechnica.com/security/2013/11/how-an-epic-blunder-...
  • anonymous 13y ago
    Actually you maybe don't even need the key. I don't know what algorithm Adobe used to encrypt these passwords, but for most standard ones it holds that if you have two encrypted messages A' and B' corresponding to plain texts A and B, then B = A ^ A' ^ B'. You really only need to find one password of length N to be able to decrypt all passwords with length <= N. Edit: Of course I mean two messages encrypted with the same key and initialisation vector. Do not reuse IVs kids, you'll get hurt.
    • tcas 13y ago
      That's true of stream ciphers, and if they reuse a nonce. It looks like they used 3DES which is for all intents and purposes here, immune to a this kind of attack. EDIT: If they use 3DES in a CTR mode then it could be vulnerable to this, but looking at the base64ed texts in the blog posts, they are multiples of 8 meaning it is almost certainly in a block cipher mode. Would be interesting to see if you can find any block similarities if they used ECB.
      • mischanix 13y ago
        This is really neat. Adobe stated the hashes are 3DES/ECB. So, say I have a two block password with '6aMjgZFLzYg' as the second block... when I just search for that block I see alot of hints that point to '123456789' as a password, implying the plaintext for that block is simply '9'. So now I believe the password is 9 characters long and ends with '9'.
• rmrfrmrf 13y ago
  lol; "should have used a salt" is one of the most hilarious HN memes.
  • corin_ 13y ago
    My point wasn't that using a salt is good practice, just that Adobe's method was so bad that even a salt+hash would have been better.