SHA-256 is used to create digital signatures, which ensure data integrity and authenticity. Here's how it works:

1. _Data hashing_: SHA-256 is used to calculate a hash value of the payment card data, creating a unique digital fingerprint.

2. _Digital signature creation_: The hash value is encrypted using a private key, creating a digital signature.

3. _Data transmission or storage_: The payment card data and digital signature are transmitted or stored.

4. _Verification_: The digital signature is decrypted using a public key, and the hash value is recalculated using SHA-256.

5. _Comparison_: The recalculated hash value is compared to the original hash value. If they match, the data has not been tampered with or altered.

SHA-256's properties make it ideal for digital signatures:

1. _Deterministic_: SHA-256 always produces the same hash value for the same input data.

2. _Collision-resistant_: It's computationally infeasible to find two different inputs with the same hash value.

3. _Pre-image resistant_: It's computationally infeasible to reverse-engineer the original data from the hash value.

By using SHA-256 for digital signatures, organizations can ensure the integrity and authenticity of payment card data, detecting any tampering or alterations.