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.

 

Format	Size	Ratio
Uncompressed data	3068KB	100.0%
ZIP, Deflate64 Maximum compression	966KB	31.5%
CAB, Maximum compression	844KB	27.5%
SQX2.0, ultra compression, dictionary 32MB, solid archive, multimedia & EXE compression	813KB	26.5%
7zip, ultra compression, solid archive, dictionary 96MB, word size 273B	801KB	26.1%
RAR, maximum compression, solid archive	737KB	24.0%
SITX, method 5, level 16, memory 23, optimizers on, block mode on, don't storing thumbnails	730KB	23.8%
KGB2, PAQ6, normal compression	701KB	22.9%
KGB1, normal compression	694KB	22.6%
KGB2, PAQ7, good compression	608KB	19.8%

More tests are available at test page.