KGB Archiver is the concentration tool with unbelievable high concentration rate. It surpasses even such efficient concentration tool like 7zip and UHARC in terms of the abilities. KGB Archiver is an application created to allow you to compress and decompress files.
Unfortunately although its powerful concentration 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 human.