4 ms·

I don't see how this follows -- the colours are changing with each keypress (just as an md5 digest would change if you added a letter to the message) but surely

by Torn 17y ago

I don't see how this follows -- the colours are changing with each keypress (just as an md5 digest would change if you added a letter to the message) but surely you cannot know the key pressed without brute-forcing / breaking the hash, which is computationally impractical? He's also scraping the hash for a run of 6 hex characters, so surely there's quite a few colour collisions for different hashes, making it even harder to guess which keys have been pressed?

extension 17y ago
If you know the digest after each keypress, the search space for a brute force attack is roughly alphabet size * password length, which is trivial.
chaosmachine 17y ago
Because you can see the color code at each step, it's easy to compare results very quickly, even by hand. Did I get letter 1 right? Ok, move on to letter two, try each key until the colors match the recording. Do this for each step. At most, you have to try about 64 key presses to crack each letter. Also, because each step is only 1 character different, it's very unlikely that you will get collisions, even with a truncated md5 hash.
- Torn 17y ago
  Thank-you for the clear explanation.
- liquidben 17y ago
  It strikes me that this reduces password cracking to a game of Mastermind. Amusement aside, it also allows a cracking attempt to be done without running up against server authentication. Even if the same series of color patterns can occur for multiple passwords, the quantity of attempted server authentications is greatly reduced.
  - calambrac 17y ago
    It's actually easier than Mastermind, you only have to guess one character at a time.
- beyondkaoru 17y ago
  This sounds like it would be easily fixed using a this-page-only salt for your hashing function. I.e., when someone else visits the login page, they get a different salt and thus can't use that attack. This could be done on the server (if you use a dynamically generated page) or on the client (with some javascript).
  - calambrac 17y ago
    How do you know it's "someone else"? It's the login page, you don't know who you're displaying the page to yet. And if you mean a different salt every time the page gets loaded: doesn't that completely skip the supposed point, which is to give the user a recognizable visual cue that they typed the right password?
    - Meatshoes 17y ago
      The demo seems to highlight its use as a visual cue that your confirmed password is the same as the original. Not that useful in my opinion, as one attempt at creating an account with non-matching passwords will tell you they don't match anyway, and you (usually) only create an account once. Still, pretty cool demo and very nice colour schemes.
varenc 17y ago
It completely doable. Its unlikely there will be a collision in the first 6 characters of the md5 hash of 'AAAx' where x is [a-zA-Z0-9] and AAA is known. That's only 62 hopes for collision out of a space of 2176782336 (36^6 ... right?) Think of it this way, if you capture the length of password, and the corresponding 6 hex characters, for every step of the password, that's quite a bit of information! (a quick check confirms no first 6 character collisions in a-z)

by Torn 17y ago

extension 17y ago

If you know the digest after each keypress, the search space for a brute force attack is roughly alphabet size * password length, which is trivial.

chaosmachine 17y ago

Because you can see the color code at each step, it's easy to compare results very quickly, even by hand. Did I get letter 1 right? Ok, move on to letter two, try each key until the colors match the recording. Do this for each step. At most, you have to try about 64 key presses to crack each letter. Also, because each step is only 1 character different, it's very unlikely that you will get collisions, even with a truncated md5 hash.

Torn 17y ago
Thank-you for the clear explanation.
liquidben 17y ago
It strikes me that this reduces password cracking to a game of Mastermind. Amusement aside, it also allows a cracking attempt to be done without running up against server authentication. Even if the same series of color patterns can occur for multiple passwords, the quantity of attempted server authentications is greatly reduced.
- calambrac 17y ago
  It's actually easier than Mastermind, you only have to guess one character at a time.
beyondkaoru 17y ago
This sounds like it would be easily fixed using a this-page-only salt for your hashing function. I.e., when someone else visits the login page, they get a different salt and thus can't use that attack. This could be done on the server (if you use a dynamically generated page) or on the client (with some javascript).
- calambrac 17y ago
  How do you know it's "someone else"? It's the login page, you don't know who you're displaying the page to yet. And if you mean a different salt every time the page gets loaded: doesn't that completely skip the supposed point, which is to give the user a recognizable visual cue that they typed the right password?
  - Meatshoes 17y ago
    The demo seems to highlight its use as a visual cue that your confirmed password is the same as the original. Not that useful in my opinion, as one attempt at creating an account with non-matching passwords will tell you they don't match anyway, and you (usually) only create an account once. Still, pretty cool demo and very nice colour schemes.

varenc 17y ago

It completely doable. Its unlikely there will be a collision in the first 6 characters of the md5 hash of 'AAAx' where x is [a-zA-Z0-9] and AAA is known. That's only 62 hopes for collision out of a space of 2176782336 (36^6 ... right?) Think of it this way, if you capture the length of password, and the corresponding 6 hex characters, for every step of the password, that's quite a bit of information! (a quick check confirms no first 6 character collisions in a-z)