From Tomasz Pawlak
KGB Archiver is the compression tool with an unbelievably high compression rate. Unfortunately, in spite of its powerful compression rate, it has high hardware requirements (I recommend processor with 1,5GHz clock and 256MB of RAM as an essential minimum). One of the advantages of KGB Archiver is also AES-256 encryption which is used to encrypt the archives. This is one of the strongest encryptions known for man.