AES Key Wrap

AES Key Wrap is a dedicated construction for protecting key material with a key-encryption key. It uses AES, but it is not AES-CBC or AES-GCM. It has no ordinary IV. Instead it starts from a fixed constant, A6A6A6A6A6A6A6A6, which doubles as the integrity check when the key is unwrapped.

A wrong key or tampered data therefore shows up straight away, with no separate MAC. A common mistake is to reach for raw AES-ECB to wrap keys, which brings back the pattern leakage that ECB is notorious for. If you are building key management, use the standard construction rather than inventing your own.