  We investigate the content identification problem from an information
theoretic perspective and derive its fundamental limits. Here, a rights-holder
company desires to keep track of illegal uses of its commercial content, by
utilizing resources of a security company, while securing the privacy of its
content. Due to privacy issues, the rights-holder company only reveals certain
hash values of the original content to the security company. We view the
commercial content of the rights-holder company as the codebook of an encoder
and the hash values of the content (made available to the security company) as
the codebook of a decoder, i.e., the corresponding codebooks of the encoder and
the decoder are not the same. Hence, the content identification is modelled as
a communication problem using asymmetric codebooks by an encoder and a decoder.
We further address "the privacy issue" in the content identification by adding
"security" constraints to the communication setup to prevent estimation of the
encoder codewords given the decoder codewords. By this modeling, the proposed
problem of reliable communication with asymmetric codebooks with security
constraints provides the fundamental limits of the content identification
problem. To this end, we introduce an information capacity and prove that this
capacity is equal to the operation capacity of the system under i.i.d. encoder
codewords providing the fundamental limits for content identification. As a
well known and widely studied framework, we evaluate the capacity for a binary
symmetric channel and provide closed form expressions.
