  We consider a public multi-user information embedding (watermarking) system
in which two messages (watermarks) are independently embedded into two
correlated covertexts and are transmitted through a multiple-access attack
channel. The tradeoff between the achievable embedding rates and the average
distortions for the two embedders is studied. For given distortion levels,
inner and outer bounds for the embedding capacity region are obtained in
single-letter form. Tighter bounds are also given for independent covertexts.
