Decode of Example ATR Bytes

[Good Carder]

The examples provided are from public databases of EMV-compatible Visa card ATRs. Note that while they follow the ISO/IEC 7816-3 structure in part, some appear to have additional bytes at the end (e.g., repeating values or 90 00, which may indicate a status code or CRC for contactless interfaces in some contexts). I'll decode each as per the standard structure, assuming the core ATR ends at the TCK (if required), and note any discrepancies. The decoding includes interpretations where applicable, such as clock/bit rate parameters from tables in the standard.

1. ATR: 3B 7F 13 00 00 80 31 C0 52 0A A6 64 02 B3 02 37 83 83 90 00 (Visa Classic from "La Caixa", Spain)​

• TS: 3B (Direct convention - logic '1' is high voltage, bits transmitted LSB first).
• T0: 7F (Historical bytes K = 7; indicates TA1, TB1, TC1, TD1 present).
• TA1: 13 (FI = 1: Clock rate conversion factor F = 372, max clock frequency f = 5 MHz; DI = 3: Bit rate adjustment D = 8. Results in ETU = 372/8 = 46.5 clock cycles per bit).
• TB1: 00 (II = 0: Max current = 10 mA; PI1 = 0: No VPP required).
• TC1: 00 (N = 0: No extra guard time).
• TD1: 80 (Protocol T = 0; indicates TD2 present, no TA2/TB2/TC2).
• TD2: 31 (Protocol T = 1; indicates TA3, TB3 present, no TC3/TD3).
• TA3: C0 (IFSC = 192: Information field size for the card in T=1 protocol).
• TB3: 52 (BWI = 5: Block waiting time = 2^5 * 960 ETU; CWI = 2: Character waiting time = 2^2 = 4 ETU).
• Historical bytes (K=7): 0A A6 64 02 B3 02 37 (Proprietary format; first byte 0A may be a tag or length for issuer-specific data, e.g., application or batch info).
• TCK: 83 (Check byte for integrity; computed XOR from T0 to historical end is 03, XOR with TCK = 83 gives 80 ≠ 0, so verification fails - possible list error or incomplete ATR).
• Additional bytes: 83 90 00 (Not part of standard ATR; may be CRC, status, or transcription error).

2. ATR: 3B 7F 13 00 00 80 31 C0 52 0A D6 64 05 66 94 61 83 83 90 00 (Visa credit from Caixa d'Enginyers, Spain)​

• TS: 3B (Direct convention).
• T0: 7F (K = 7; TA1, TB1, TC1, TD1 present).
• TA1: 13 (FI = 1: F = 372, f = 5 MHz; DI = 3: D = 8, ETU = 46.5 clock cycles/bit).
• TB1: 00 (II = 0, PI1 = 0: Default current, no VPP).
• TC1: 00 (N = 0).
• TD1: 80 (T = 0; TD2 present).
• TD2: 31 (T = 1; TA3, TB3 present).
• TA3: C0 (IFSC = 192).
• TB3: 52 (BWI = 5, CWI = 2).
• Historical bytes (K=7): 0A D6 64 05 66 94 61 (Proprietary; likely issuer-specific, e.g., batch or card ID data).
• TCK: 83 (Verification: Computed XOR to historical = 1B, with TCK = 83 gives 98 ≠ 0 - fails, possible error).
• Additional bytes: 83 90 00 (Likely not part of ATR).

3. ATR: 3B 67 00 00 A6 40 40 00 09 90 00 (Visa Classic from Landkreditt Bank or DNBNor, Norway)​

• TS: 3B (Direct convention).
• T0: 67 (K = 6; no TA1, TB1/TC1/TD1 present).
• TB1: 00 (II = 0, PI1 = 0).
• TC1: 00 (N = 0).
• TD1: A6 (T = 6; TB2/TD2 present, no TA2/TC2).
• TB2: 40 (II = 4, PI1 = 0; proprietary or voltage info).
• TD2: 40 (T = 0; TC3 present, no TA3/TB3/TD3).
• TC3: 00 (Character waiting time or proprietary for T=1).
• Historical bytes (K=6): 09 90 00 (Proprietary; short, possibly truncated in list as ATR has only 3 bytes here - K=6 discrepancy, list may be incomplete).
• TCK: Not present (T=0 dominant, but T=6 indicated - standard requires TCK, but none fits; possible list error or synchronous card variant).
• Additional bytes: None, but length mismatch suggests partial ATR.

4. ATR: 3B 65 00 00 20 63 CB 68 00 (Visa credit from Skandiabanken or Banque Populaire, France)​

• TS: 3B (Direct convention).
• T0: 65 (K = 5; no TA1, TB1/TC1 present, no TD1).
• TB1: 00 (II = 0, PI1 = 0).
• TC1: 00 (N = 0).
• Historical bytes (K=5): 20 63 CB 68 00 (Proprietary; first byte 20 may be tag for card service data, e.g., application selection).
• TCK: Not present (No TD bytes, so T=0 only assumed).
• Additional bytes: None.

5. ATR: 3B 68 00 00 00 73 C8 40 11 00 90 00 (Visa Classic from Nordlandsbanken, Norway)​

• TS: 3B (Direct convention).
• T0: 68 (K = 6; no TA1, TB1/TC1 present, no TD1).
• TB1: 00 (II = 0, PI1 = 0).
• TC1: 00 (N = 0).
• Historical bytes (K=6): 00 73 C8 40 11 00 (Proprietary).
• TCK: Not present (T=0 only).
• Additional bytes: 90 00 (Likely not part of ATR; common success status in EMV commands).

These decodes are based on the ISO/IEC 7816-3 standard. In practice, EMV cards may have proprietary extensions in historical bytes (often TLV-encoded for card capabilities, issuer ID, etc.). If the ATRs are from contactless interfaces, they may be ATS messages with similar structure but appended CRC bytes, which could explain the extra bytes in some examples. For exact verification or generation, physical card access or manufacturer specs are recommended.