Patent ID: 8054969

Claim:
A method of communicating a digital message with a first audio signal, the method comprising: encoding the first audio signal at a first telecommunications endpoint, via a model-based audio coder, resulting in an encoded audio signal having a frame that is M bits in length; calculating an authentication code dependent on at least a portion of the encoded audio signal, a shared key, and a hashing algorithm, resulting in the digital message comprising the authentication code; substituting a predetermined combination of N bits within the M-bit frame of the encoded audio signal with at least a portion of the digital message, wherein substituting the predetermined combination of N bits is based on a bit position, as encoded by the model-based audio coder, of each of the N bits within the M-bit frame of the encoded audio signal, and wherein the substitution of the N bits results in a composite signal; and transmitting the composite signal from the first telecommunications endpoint to a second telecommunications endpoint, thereby providing the authentication code to the second telecommunications endpoint in order to authenticate the composite signal; wherein M and N are positive integers and N is less than M.