Under the form requirements for storing secret and private keys, which method is acceptable for protecting keys used to encrypt/decrypt cardholder data?

Under the form requirements for storing secret and private keys, which method is acceptable for protecting keys used to encrypt/decrypt cardholder data?

• A. Stored in plaintext on the server.
• B. Shared with contractors.
• C. Encrypted with a key-encrypting key that is at least as strong as the data-encrypting key, and stored separately from the data-encrypting key.
• D. Stored within a secure cryptographic device.

Answer: (C)

Key management for protecting keys that encrypt cardholder data relies on layering and separation. The best approach is to protect the data-encryption key by encrypting it with a key-encrypting key that is as strong as or stronger than the data-encryption key, and then store that key-encrypting key separately from the data-encryption key. This creates two independent protections: even if the data-encryption key is exposed, the data remains unreadable without the KEK, and access to the KEK is controlled and kept in a separate secure location. The KEK should be managed in a secure cryptographic facility (such as a hardware security module) with strong access controls. Why this is preferable to the other options: storing keys in plaintext on the server is insecure and directly exposes secrets; sharing keys with contractors expands the circle of risk and violates strict access controls; while storing keys in a secure cryptographic device is a good practice, the form requirement specifically emphasizes encrypting the data-encryption key with a KEK and separating the KEK from the DEK to achieve layered protection.

Key management for protecting keys that encrypt cardholder data relies on layering and separation. The best approach is to protect the data-encryption key by encrypting it with a key-encrypting key that is as strong as or stronger than the data-encryption key, and then store that key-encrypting key separately from the data-encryption key. This creates two independent protections: even if the data-encryption key is exposed, the data remains unreadable without the KEK, and access to the KEK is controlled and kept in a separate secure location. The KEK should be managed in a secure cryptographic facility (such as a hardware security module) with strong access controls.

Why this is preferable to the other options: storing keys in plaintext on the server is insecure and directly exposes secrets; sharing keys with contractors expands the circle of risk and violates strict access controls; while storing keys in a secure cryptographic device is a good practice, the form requirement specifically emphasizes encrypting the data-encryption key with a KEK and separating the KEK from the DEK to achieve layered protection.