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MAC Calculator

ISO/IEC 9797-1 MAC Algorithm 3 (Retail MAC) — DES CBC-MAC with final 3DES output transformation

🔏 Input

Double-length DES key: K1 (first 8 bytes) ‖ K2 (last 8 bytes). Spaces are allowed.

Hex data to authenticate. Spaces are allowed.

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📖 About This Tool

What is the MAC Calculator?

The MAC Calculator computes ISO/IEC 9797-1 MAC Algorithm 3 values using DES/3DES keys. This MAC algorithm is widely used in payment systems for message authentication in ISO 8583 authorization messages.

🛠️ How to Use
  1. Enter your hexadecimal MAC key.
  2. Enter your hexadecimal data.
  3. Select the padding method.
  4. Click Calculate to compute the MAC.
❓ FAQ

What is MAC Algorithm 3?

MAC Algorithm 3 (also known as Retail MAC or ANSI X9.19) uses single DES for intermediate blocks and 3DES for the final block, providing a balance of security and performance for payment message authentication.