A method for testing an HMAC implementation for vulnerability to a side-channel attack can include mounting a template attack. The attack can include generating, based on first side-channel leakage information associated with execution of a hash function of the HMAC implementation, a plurality of template tables. Each template table can correspond, respectively, with a subset of bit positions of an internal state of the hash function. The attack can further include generating, based on second side-channel leakage information, a plurality of hypotheses for an internal state of an invocation of the hash function based on a secret key. The method can further include generating, using the hash function, respective hash values generated from each of the plurality of hypotheses and a message. The method can also include comparing each of the respective hash values with a hash value generated using the secret key to determine vulnerability of the HMAC implementation.