For those who lost their windows password...

[Max_87]

http://ophcrack.sourceforge.net/

[Chai]

Hmm...isn't this a bad thing?

[Max_87]

Depends on what you use it for

[peaz]

useful for admins who always get calls of lost password. LOL!

[Chai]

Originally Posted by peaz

useful for admins who always get calls of lost password. LOL!

Luckily we have AD...

[Adrian Wong]

Hmm.. Is this based on the dictionary? Or just brute-force?

[jamotto]

It's Greek to me, but maybe some one will understand it.

Rainbow tables are a refinement of an earlier, simpler, but less efficient algorithm that used the inversion of hashes by looking up precomputed hash chains.

Each table depends on the hash function and the reduce function used. The reduce function is a surjective ("onto") function which maps a hash to a password using the desired character set and password length. Therefore, a reduce function for lowercase alphanumeric passwords of 8 characters length is different than a reduce function for case-sensitive alphanumeric passwords of 5-16 characters length.

A chain is a sequence of passwords. A starting password is chosen, and the following is done to get the next one in the chain:

reduce( hash(a password) ) -> next password

After a chain containing a suitable number of passwords is created, the final password in the chain is hashed, and the final hash and the starting password are stored together in the rainbow table.

To reverse a hash, look for it in the table. If it isn't found, the following is done to get another hash to try:

hash( reduce(a hash) ) -> next hash


This is repeated until a hash is finally found in the table.

When a match is found, the original password that started the chain that ended with that hash can then be used to generate all the other passwords, and hence hashes, in the chain. Each of the hashes thus generated will be checked to against the original target hash, thus hopefully revealing the correct password.

The end result is a table that contains statistically high chance of revealing a password within a short period of time, generally less than a minute. The success probability of the table depends on the parameters used to generate it. These include the character set used, password length, chain length, and table count.

Success probability is defined as the probability that the plaintext can be found for a given ciphertext. In the case of passwords, the password is the plaintext, and the hash of the password is the ciphertext, so the success probability is the probability that the original password can be recovered from the password hash.

Link

[Adrian Wong]

Wow.. It's Greek to me too!

But this sounds good - "The end result is a table that contains statistically high chance of revealing a password within a short period of time, generally less than a minute."

[Chai]

Wow, greek, but impressive!

[Dashken]

Wow... nice...