PCI DSS 3.5.1.1: Keyed Cryptographic Hashes for PAN
Control 3.5.1.1 mandates that if hashing is your PAN protection method, you must use keyed cryptographic hashes of the entire Primary Account Number. This critical requirement ensures that hashed PAN data cannot be reverse-engineered or cracked through common attacks, protecting cardholder data at rest.
What this means
When you choose hashing as a PAN masking technique, the hash must be cryptographic (not simple checksums), use a secret key unknown to potential attackers, and cover the entire 16-digit PAN—not partial digits. This prevents rainbow table attacks and ensures compliance with PCI DSS encryption and tokenization standards for data protection.
How to comply
- 1.Select a FIPS-approved cryptographic hash algorithm (SHA-256 or higher) for PAN hashing
- 2.Generate and securely store a unique cryptographic key separate from the hashed PAN data
- 3.Hash the complete, untruncated PAN using the keyed hash function before storage
- 4.Implement key rotation policies to change hashing keys at least annually
- 5.Document all systems and applications using keyed PAN hashes in your data inventory
- 6.Test hash integrity and collision resistance during annual security assessments
Evidence auditors look for
- Cryptographic hash configuration documentation showing algorithm type and key length
- Key management policy demonstrating secure key generation, storage, and rotation schedules
- Database schema audit confirming hashed PAN fields and exclusion of plaintext PAN storage
- Encryption key inventory with dates of creation, rotation, and destruction
- Penetration test results validating that hashed PAN cannot be reversed or cracked
- System access logs showing restricted access to cryptographic keys and hashing systems
Frequently asked questions
When will FAQs be available?
The FAQ for this control is currently being prepared.
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