Test only password on rar archive

Question

I'm trying to do a bruteforce attack on a rar archive and I need the password-check to be as fast as possible. I call rarlab's "unrar" command line utility from my program in this way:

unrar t -p[password] archive.rar

And it works, but is extremely slow. The encrypted file inside the archive is about 300MB big, and unrar utility tells me there's a CRC error (wrong password) only after testing the whole file size. (which takes 10-15 secs)

Is there a quicker way to test just the archive password?

Harlanharland

This should be quicker rarcrack.sourceforge.net – Paulie

Answer 1

See

How to crack AES-128 encryption used in WinRar?

As to your question, no, there is no way to test just the password. The password is not stored in the encrypted archive file. AFAIK, any password you give, combined with the encrypted data, will produce decrypted data. In one universe or another, the decrypted data represent a valid RAR archive. CRC checks that the archive can be considered valid, if it fails, this means the universe in which the password is valid is not the same as your universe ;)

Seen

Answer 2

Look with rar l if the archive contains more files than the "main" file you'd like to extract. There are usually .txt or .nfo files contained in the archive with few KB-s. You can then execute brute force attack to extract only the smallest file in archive with rar -ppassword x <archive> <file> what should be much faster.

Hullo