Steganographic techniques

Modern steganography entered the world in 1985 with the advent of the Personal Computer applied to classical steganography problems. Development following that was slow, but has since taken off, based upon the number of 'stego' programs available.

* Concealing messages within the lowest bits of noisy images or sound files.
* Concealing data within encrypted data. The data to be concealed is first encrypted before being used to overwrite part of a much larger block of encrypted data.
* Chaffing and winnowing
* Mimic functions convert one file to have the statistical profile of another.

This can thwart statistical methods that help brute-force attacks identify the right solution in a ciphertext-only attack.
* Invisible ink
* Null ciphers
* Concealed messages in tampered executable files, exploiting redundancy in the i386 instruction set
* Embedded pictures in video material (optionally played at slower or faster speed).
* A new steganographic technique involves injecting imperceptible delays to packets sent over the network from the keyboard. Delays in keypresses in some applications (telnet or remote desktop software) can mean a delay in packets, and the delays in the packets can be used to encode data.
* Content-Aware Steganography hides information in the semantics a human user assigns to a datagram; these systems offer security against a non-human adversary/warden.
* BPCS-Steganography - a very large embedding capacity steganography.
* Blog-Steganography. Messages are fractionalyzed and the (encrypted) pieces are added as comments of orphaned web-logs (or pin boards on social network platforms). In this case the selection of blogs is the symmetric key that sender and recipient are using. The carrier of the hidden message is the whole blogosphere.