Hidden encrypted messages

[derek@cs.wisc.edu (Derek Zahn)]

If true encryption is ever outlawed in the U.S., I wonder if it's
possible to have an encryption technique that preserves plausible
deniability.  That is, if seemingly innocuous messages could contain
encrypted messages (for example, first-letter-of-words strung
together).  In such a case, I'd think that it would be difficult
to prove that said message contained a hidden message unless the
decryption key was available (the embedded encrypted message wouldn't
look suspicious, even if an onlooker knew where to look).  Is
this a common idea in cryptographic circles?

derek