Steghide is a steganography program which embeds a secret message
in a cover file by replacing some of the least significant bits of
the cover file with bits of the secret message. After that, the
secret message is imperceptible and can only be extracted with the
correct passphrase. To increase invisibility the hidden bits are
encrypted (using the blowfish encryption algorithm) and
pseudo-randomly spread in the stego file. Steghide is able to
embed data in BMP, WAV and AU files.