Last week I found an archive with some important documents on my hard disk, but it was password protected. Unfortunately, I didn't remember the password, so I tried to find a good software to recover the password even if that meant brute-force attack.
Elcomsoft has many programs for password recovery that have many great features and are free for personal (non-commercial) use.
* For ZIP, brute-force attack speed is up to fifteen million passwords per second. The brute force attack is the slowest method of password attack, but can often be successful on short and simple passwords.
* Dictionary-based attack (with word mutations) is available. That's the most effective way to recover a password. English, French, German, Japanese (and many others) dictionaries with hundreds of thousands of words, as well as specialist, technical and foreign language dictionaries are available.
* Fast known-plaintext attack (it takes 10-15 minutes).
* The programs can work in the background, using the CPU only when it is in idle state.
There is no guarantee that the password will be recovered, but most people use short and/or easy to remember passwords. My password had only 6 characters so it was found in less than 2 minutes.
You can recover passwords for archives (ZIP, RAR, ACE), Office documents, instant messangers, files encrypted on NTFS (EFS) partitions. Although they say the free versions are available as 30 days trials, they can be used after this period (with some limitations).
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