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.