Cryptographic Token Interface Standard

PKCS#11

AES Key Wrap

The mechanisms support only single-part operations, single part wrapping and unwrapping, and single-part encryption and decryption.

The CKM_AES_KEY_WRAP mechanism can wrap a key of any length. A key whose length is not a multiple of the AES Key Wrap block size (8 bytes) will be zero padded to fit. The CKM_AES_KEY_WRAP mechanism can only encrypt a block of data whose size is an exact multiple of the AES Key Wrap algorithm block size.

The CKM_AES_KEY_WRAP_PAD mechanism can wrap a key or block of data of any length. It does the usual padding of inputs (keys or data blocks) that are not multiples of the AES Key Wrap algorithm block size, always producing wrapped output that is larger than the input key/data to be wrapped. This padding is done by the token before being passed to the AES key wrap algorithm, which adds an 8 byte AES Key Wrap algorithm block of data.