ICC Data (EMV)
What it is
DE 55 carries the chip transaction: BER-TLV encoded EMV tags produced by the card and terminal. The critical ones are 9F26 (Application Cryptogram — the ARQC the issuer validates), 9F27 (cryptogram information data), 82 (AIP), 95 (TVR), 9A/9F21 (date/time), 9F02 (amount), 9F37 (unpredictable number), and 5F34 (PAN sequence). The response carries issuer authentication data (91) and scripts (71/72) back to the card.
Every network wraps the same TLV payload slightly differently (Mastercard DE 55, Visa field 55 usage, some domestic switches use DE 48). Decode the payload with the EMV TLV decoder; validate cryptograms with the ARQC calculator.
Example values
9F2608AABBCCDD11223344 9F2701 80 9505 0000048000ARQC, CID=80 (ARQC requested), and TVR with offline data authentication failed bit.Specification reference
Defined in ISO 8583:1987 (base). Card networks publish their own dialect tables (Visa BASE I / V.I.P., Mastercard CIS) that refine formats, lengths, and — for private-use elements — the entire layout. Always confirm against the interface specification you implement.