SHA-256 is used in secure key management to ensure the integrity and confidentiality of encryption keys, which are used to protect payment card data. Here's how:

1. _Key generation_: SHA-256 is used to generate a unique and secure encryption key.

2. _Key hashing_: SHA-256 is used to hash the encryption key, creating a digital fingerprint.

3. _Key storage_: The hashed key is stored securely, often in a Hardware Security Module (HSM) or a secure key store.

4. _Key verification_: When the key is needed, SHA-256 is used to re-hash the key and verify that it matches the original hash value.

5. _Key usage_: The verified key is used to encrypt or decrypt payment card data.

SHA-256's properties ensure secure key management:

1. _Uniqueness_: SHA-256 generates unique hash values, preventing key duplication.

2. _Irreversibility_: SHA-256's one-way hashing makes it impossible to reverse-engineer the original key from the hash value.

3. _Collision resistance_: SHA-256's collision resistance ensures that different keys will not produce the same hash value.

By using SHA-256 in secure key management, organizations can ensure that only authorized parties can access and decrypt payment card data, maintaining the confidentiality and integrity of sensitive information.