Keep it open while you decode DE55. Search by tag or by keyword.
| Tag | Meaning |
|---|
DE55 carries BER-TLV: each item is a Tag, a Length and a Value, laid end to end. Tags are one or two bytes — you tell which by the low five bits of the first byte. If they are all ones (0x1F), another byte follows. That is why you see two-byte tags like 9F26.
When troubleshooting an authorization, a handful come up constantly: 9F26 application cryptogram (ARQC/TC/AAC, the core proof of a chip transaction), 9F27 cryptogram information data (whether the chip is recommending approval or decline), 95 terminal verification results (TVR — five bytes of flags, each bit a check that failed), 82 application interchange profile (what the card supports), and 9F34 CVM results (how the cardholder was verified).
57 (track 2 equivalent data) and 5A (application PAN) — that is cardholder data. Those must be masked in logs, tickets and screenshots; they are equivalent to the card number and fall squarely under PCI DSS.Many tags carry bit strings rather than readable text — TVR, AIP and CVM Results among them — and only mean something once decoded bit by bit. The parser on this site translates those into plain language automatically. If you just need to confirm what a tag is, the table above is faster.