A variety of techniques for steganographically encoding digital data into, and decoding steganographically data from, audio, video, and image signals ("content signals") are disclosed. One method encodes a sampled input signal in a manner wherein a single signal sample is processed in accordance with plural bits of binary data. Another technique globally distributes a plural-bit code throughout a content signal, so that the code can be fully discerned from an analysis of even a fraction of the encoded signal, and wherein the encoding takes the form of low level pseudo-random noise. Another technique involves decoding steganographic data from an encoded content signal without reference to an unencoded version of the content signal. A variety of other techniques are also disclosed.