In my question (and answer) about a partial hash code used within a signature application I found out that partial hash codes are sometimes used within protocols with a relatively restricted security tokens such as smart cards.
In the comments below the answer I mused that the partial hash makes sense over a full hash. If a octet string representing a full hash is send then the octet string can contain any data, which would then be used in the signature scheme instead of the hash. This way it could be possible to create a covert channel.
Two related questions:
- Are covert channels considered a significant threat in signature schemes?
- Are partial hashes used in other protocols than the one described above?