It's most unique characteristic, however, is that compression with bicom is completely bijective -- any file is a possible bicom output that can be decompressed, and then recompressed back to its original form. Of course, any file is also a possible bicom input that can be compressed, and then decompressed back to its original form. At the time of its release, bicom is the only competitive compressor with this quality.

If you consider compression to be an important first step before encryption, because it minimizes redundancy in the plaintext, then you can appreciate this bijective quality, because bijectivity implies that the compression adds no known plaintext to its output.

To support encryption applications, bicom also includes a passphrase-protection option that will automatically encrypt after compressing, or decrypt before decompressing. The cipher used is the current AES proposal, Rijndael. It is applied in a unique way, however, that preserves the bijective property of the compressor, and almost never changes the size of a compressed file.