The AES XTS context to which the key should be bound.
key
The encryption key. This is comprised of the XTS key1 concatenated with the XTS key2.
keybits
The size of \p key passed in bits. Valid options are: 256 bits (each of key1 and key2 is a 128-bit key) 512 bits (each of key1 and key2 is a 256-bit key)
Return value
\c 0 on success. #MBEDTLS_ERR_AES_INVALID_KEY_LENGTH on failure.