Since fingerprint data are no secrets but of public nature, the verification data transmitted to a smartcard for oncardmatching need protection by appropriate means in order to assure data origin in the biometric sensor and to prevent bypassing the sensor. For this purpose, the verification data to be transferred to the user smartcard is protected with a cryptographic checksum that is calculated within a separate security module controlled by a tamper resistant card terminal with integrated biometric sensor. Keywords authentication, biometrics, cryptographic protocols, data integrity, electronic signature, oncard-matching, smartcards, system security, tamper proof environment