PCI-DSS says 112 bits of security is "strong cryptography", just so people can continue using 3DES.
- Block size <- YOU ARE HERE
- Cipher mode
- Cipher construction and integrity checks (for non-AEAD modes)
- Key exchange
You can break 256 bit AES if you're using 256-bit classical Diffie Hellman, for example. "But AES has 256 bits of security!" is somewhat silly to argue in such a hypothetical protocol.This is one reason why you're better off ignoring PCI-DSS when it comes to cryptography guidelines (aside from maintaining compliance where you have obligations to remain compliant, of course).