EMV Tag Decoder

What are Bit-Mapped EMV Tags?

Many EMV tags contain bit-mapped values where each bit position represents a specific feature, capability, or status. Understanding these bit mappings is crucial for debugging EMV transactions and understanding transaction flows.

Common Bit-Mapped EMV Tags

• Application Interchange Profile (AIP, Tag 82): Indicates the capabilities of the card, such as SDA, DDA, CDA support, and cardholder verification methods.
• Terminal Verification Results (TVR, Tag 95): Records the results of various card processing checks performed by the terminal.
• Transaction Status Information (TSI, Tag 9B): Indicates which functions were performed during the transaction.
• Cardholder Verification Method (CVM) List (Tag 8E): Specifies the prioritized list of CVM methods supported by the card.
• Terminal Capabilities (Tag 9F33): Indicates the card data input, CVM, and security capabilities of the terminal.
• Additional Terminal Capabilities (Tag 9F40): Indicates the data input and output capabilities of the terminal.
• Terminal Transaction Qualifiers (TTQ, Tag 9F66): Indicates reader capabilities, transaction requirements, and terminal risk management settings.
• Card Transaction Qualifiers (CTQ, Tag 9F6C): Indicates card capabilities, transaction requirements, and card risk management settings.

Reading Bit-Mapped Values

Bit-mapped values are typically represented in hexadecimal format. To interpret them:

1. Convert the hexadecimal value to binary
2. Read the binary value from left to right (most significant bit to least significant bit)
3. Check each bit position against the tag's bit mapping specification
4. A bit value of 1 typically indicates that a feature is supported, enabled, or a condition is true

Example: Application Interchange Profile (AIP)

For example, an AIP value of "5800" in hexadecimal converts to "0101100000000000" in binary, which indicates:

• Bit 1 (0): SDA is not supported
• Bit 2 (1): DDA is supported
• Bit 3 (0): Cardholder verification is not supported
• Bit 4 (1): Terminal risk management is to be performed
• Bit 5 (1): Issuer authentication is supported
• Bit 6 (0): CDA is not supported
• Remaining bits (all 0): Reserved for future use

Importance in Transaction Processing

Understanding these bit mappings is essential for:

• Transaction Debugging: Identifying why a transaction was approved, declined, or required online authorization
• Terminal Configuration: Ensuring terminals are properly configured to support the required capabilities
• Compliance Testing: Verifying that cards and terminals comply with EMV specifications
• Risk Management: Understanding the security features used in a transaction