Where it appears
Returned by the card alongside the ACApplication CryptogramA cryptogram the card generates to approve or decline a transaction: TC (approve offline), ARQC (go online), or AAC (decline). in the GENERATE ACApplication CryptogramA cryptogram the card generates to approve or decline a transaction: TC (approve offline), ARQC (go online), or AAC (decline). response.
Specification reference
Defined in: EMV 4.x Book 3 (Application Specification), Annex A — Data Element Dictionary
Bit-level definitions below follow: EMV 4.4 Book 3, §6.5.5.4, Table 15 — Cryptogram Information Data (1 byte)
Bit & value breakdown
EMV 4.4 Book 3, §6.5.5.4, Table 15 — Cryptogram Information Data (1 byte)
Bits b8–b7 (cryptogram type)
b8–b7 = 00AAC — Application Authentication Cryptogram (transaction declined)b8–b7 = 01TC — Transaction Certificate (transaction approved offline)b8–b7 = 11RFUReserved for Future UseBits or bytes with no current meaning, reserved by the spec; they must be set to zero.Bits b6–b1
b6–b5Payment system-specific cryptogramb3–b1 = 000Reason / advice code: no information givenb3–b1 = 001Service not allowedb3–b1 = 010PIN Try Limit exceededb3–b1 = 011Issuer authentication failedb3–b1 = 1xxRFUReserved for Future UseBits or bytes with no current meaning, reserved by the spec; they must be set to zero.Common full-byte values
0x00AAC (0000 0000) — decline0x40TC (0100 0000) — offline approvalExample values
80ARQC — request online authorisation
40TC — approved offline
00AAC — declined