Hash Decrypt

How can I decrypt a variable once it has been encryted in sha1 or md5?

SHA1 and MD5 are hash algorithms, i.e. they do not encrypt your value. One of the goals of hashing algorithms is to give you a hard time to reverse them.

Decrypting is only possible with a dictonary attack or by bruteforce.

This is not true. Hashes are non-reversable. This is also true for weak hashing algorithms, the problem with those is, that you don’t actually have to find the original plain text, any collision will do.

@topic: You could also use rainbow tables. But as already said, you can’t decrypt a hash.

Toss the hashes into Google. md5 and sha1 are widespread hash methods, so if the hashed value is common, chances are good something comes up.

Hashes are irreversable but with modern hardware you can bruteforce even sha256 very fast.