EMV Contactless Cryptograms – The Complete Technical Guide 2026

[Student]

(From EMVCo Contactless Kernel Specs, Visa payWave, Mastercard Contactless, and 2025 reports – December 2025)

EMV contactless payments (tap-to-pay) use NFC (ISO 14443) for fast transactions. The core security is dynamic cryptograms – unique per-transaction codes that prevent cloning/replay.

In 2025, contactless is >80 % of in-store payments globally (EMVCo). Cryptograms are generated by the card/chip using session keys + unpredictable data.

Key Cryptogram Types in EMV Contactless (All Schemes)​

Type	Tag	Length	When Generated	Purpose	Real 2025 Use
ARQC	9F26	8 bytes	Online authorization request	Issuer validates card + transaction	Most transactions
TC	9F26	8 bytes	Offline approval	Terminal approves locally	Offline terminals (rare)
AAC	9F26	8 bytes	Decline	Terminal declines	Fraud/risk
CID	9F27	1 byte	With cryptogram	Indicates type (80=ARQC, 40=TC, 00=AAC)	Always

Fast modes (Visa Quick Chip, Mastercard M/Chip Fast, Amex Quick Chip) often skip ARPC (issuer response cryptogram) for speed.

How Contactless Cryptograms Are Generated (General EMV Flow)​

1. Terminal sends GENERATE AC command with:
   • Unpredictable Number (UN)
   • Amount
   • Terminal data (CDOL1/PDOL)
2. Card derives session key from master key + ATC + UN
3. Card builds data block (transaction + card data)
4. Card MACs data block with session key → ARQC
5. Terminal sends ARQC to issuer → validated → approval + optional ARPC
6. Fast contactless: Often no ARPC – trust card decision.

Scheme-Specific Differences in Contactless Cryptograms (2025)​

Scheme	Cryptogram Version	Key Features	Data Block	Fast Mode	Real 2025 Notes
Visa payWave	CVN 10/18/22 (22 dominant)	UDK + session key	Extended for CVN22	Quick Chip (no ARPC)	ECC-ready, inductive coupling
Mastercard Contactless	M/Chip Advance	CSK/SKD + session	Proprietary	M/Chip Fast (no ARPC)	Strong CDA
Amex Expresspay	Proprietary	Secret derivation	Proprietary	Quick Chip	On-behalf validation
Discover Zip	D-PAS proprietary	Secret	Proprietary	Zip (no ARPC)	Limited public specs
EMVCo C-8 Kernel (new unified)	Unified (ECC + AES)	Standard + extensions	Common + scheme-specific	All fast modes	Emerging 2025–2026

EMVCo C-8 Kernel (new 2025 unified contactless spec):

• Supports ECC + AES secure channel
• Common base for all schemes → reduces kernel complexity
• Cryptogram generation standardized but scheme extensions allowed

Real Example – Visa payWave Contactless ARQC (From Test Data)​

GENERATE AC command:

80 AE 50 00 28 00 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 12 34 56 78 90 AB CD EF 00

Response (ARQC):

77 39 9F 27 01 80 9F 36 02 00 01 9F 26 08 A1 B2 C3 D4 E5 F6 78 90 9F 10 13 06 01 0A 03 A0 00 00 10 01 00 00 00 00 00 00 00 00 00 90 00

Decoded:

• ARQC (9F26): A1 B2 C3 D4 E5 F6 78 90
• CID (9F27): 80 (ARQC)

Bottom Line – December 2025​

Contactless cryptograms in 2025 are dynamic, scheme-specific MACs that make replay/cloning impossible on online terminals. Fast modes (Quick Chip, M/Chip Fast) skip ARPC for speed. New EMVCo C-8 kernel standardizes base while allowing scheme extensions.

Real security is very high for normal use.

Want legitimate EMV research tools? DM for “EMV Contactless Pack December 2025”:

• Public test vectors
• Kernel spec excerpts
• Research papers

Stay safe – contactless is secure.

Your choice.