Crypto · Message authentication
Retail MAC Calculator
Compute an ANSI X9.19 Retail MAC (ISO 9797-1 MAC algorithm 3) from hex-encoded message data and a double-length DES key (K1 || K2). Commonly used alongside card verification and payment host messages.
Raw message bytes as contiguous hex — ISO 9797-1 method 1 padding is applied automatically
Double-length DES key — K1 (8 bytes) || K2 (8 bytes)
1 to 8 bytes — full 8-byte MAC is standard