Patent ID: 8185738

Claim:
A method, comprising: producing with a first electronic device, from data to be sent to a second electronic device, an authentication code including authentication bits; generating, from the authentication code, a signature including a subset of the authentication bits of the authentication code, the authentication code having a length that is greater than a length of the signature, and the authentication code including hidden bits which are not inserted into the signature; sending to the second electronic device the data and the signature, and not sending each bit of the authentication code, so that hidden bits of authentication code which are not inserted into the signature are not sent; receiving an acknowledgement from the second electronic device; and producing an internal acknowledgement by using the hidden bits of the authentication code; and determining the authenticity of the received acknowledgement by comparing the received acknowledgement with the internal acknowledgement by checking that at least some of the hidden bits of the authentication code are in the received acknowledgement.