  We develop the notion of a locally homomorphic channel and prove an
approximate equivalence between those and codes for computing functions.
Further, we derive decomposition properties of locally homomorphic channels
which we use to analyze and construct codes where two messages must be encoded
independently. This leads to new results for identification and
K-identification when all messages are sent over multiple-access channels,
which yield surprising rate improvements compared to naive code constructions.
In particular, we demonstrate that for the example of identification with
deterministic encoders, both encoders can be constructed independently.
