Greetings and Salutations: In my first e-mail I meant to congratulate Dan Kaminsky for the fine work and write-up he did. Excellent. On 12/7/04 10:01 PM, "David Schwartz" <davids@xxxxxxxxxxxxx> wrote: >> From my reading it appears that you need the original source to create the >> doppelganger blocks. It also appears that given a MD5 hash you could not >> create a input that would give that MD5 back. Passwords encoded with MD5 >> would not fall prey to your discovery. Is this correct? > > Correct. You will never be able to find the input given an MD5 hash. It > might be possible to, eventually, come up with an input that has the same > hash given just the hash, but you could never know if that was the original > input or not. (At least, not in general.) That is the worry that I have for MD5 hashed passwords. It doesn't matter that you get the *correct* password, just that you have input that will hash (collide) to the correct MD5 hash. What I am worried about is the integrity of MD5 hashed passwords. This concern is for both Cisco and *NIX passwords. Lets say that I have a password: "ThisIsMySecretPassphrase" MD5 = $1$Vjuf$t5QYnzXL0Sy4tThvqKDGa1 Lets say that I am very smart and I can use software that is able to generate a collision in the passwords such that the MD5 hashes are the same, say for example: "AshEr37WesW28Er4E2" MD5 = $1$Vjuf$t5QYnzXL0Sy4tThvqKDGa1 It does not matter that I don't know the correct password, I have a password that collides into the correct hash. I can log into the system with my generated password. I just want to make sure that the MD5 hash passwords don't end up being as easy to compute as the Cisco 7 passwords or the NTLM passwords. It actually is beginning to sound like there might be enough of a hole in MD5 that "we" (collectively) had better start working on SHA-2 hashed passwords ... Ken --------------------------------------------------------------- Do not meddle in the affairs of wizards for they are subtle and quick to anger. Ken Hollis - Gandalf The White - gandalf@xxxxxxxxxxx - O- TINLC WWW Page - http://digital.net/~gandalf/ Trace E-Mail forgery - http://digital.net/~gandalf/spamfaq.html Trolls crossposts - http://digital.net/~gandalf/trollfaq.html
