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AAV Decoder

Decode Mastercard Accountholder Authentication Value (UCAF) — 3D Secure / Identity Check

🔐 Input

Enter a Base64 string or 40-character hex string (20 bytes). Spaces in hex are OK.

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📖 About This Tool

What is the AAV Decoder?

The AAV Decoder parses Accountholder Authentication Value data used in Mastercard SecureCode (3D Secure) authentication. It decodes the UCAF format including the control byte, ACS identifier, and authentication data.

🛠️ How to Use
  1. Enter the AAV/UCAF value.
  2. Click Decode to parse all component fields.
❓ FAQ

What is an AAV?

AAV (Accountholder Authentication Value) is Mastercard's equivalent of Visa's CAVV. It is a cryptographic value in the UCAF (Universal Cardholder Authentication Field) that proves the cardholder was authenticated via Mastercard SecureCode / Mastercard Identity Check.