codenthink
codenthink

Reputation: 62

Can I decode an md5 code without knowing the one character?

How can I decode this MD5 hash, if I don't know where a char is missing? 0fa605e479e7cd896f9bc33cccba944

Upvotes: 0

Views: 388

Answers (2)

GavinH
GavinH

Reputation: 2213

Firstly, the missing character.

There are 16 possible values that the character could take (0-f), and there are 32 possible positions that the character could take. This means there are 16 * 32 = 512 different combinations to try.

Secondly, the "decoding".

MD5 is a hash function, which means it is designed to be a one way transformation and can't be decoded. However, MD5 used to be very popular for storing passwords so people have created databases of the hashed values for doing reverse lookups.

If you were super keen and you think the original value might be a dictionary word, you could do a reverse lookup on all 512 possibilites.

Upvotes: 1

Samuel Neff
Samuel Neff

Reputation: 74909

You can sometimes "decode" an MD5 hash using a rainbow table. This is basically a list of every possible combination of letters/numbers and the resulting hash values. This is not really "decoding" per se, but it is effectively the same thing.

Here's one sample:

https://crackstation.net/

However, with a missing character, it's really impossible. Too many variations even to look up in a rainbow table.

Upvotes: 2

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