Documentation
# SM4-OFB cipher from: https://datatracker.ietf.org/doc/html/draft-ribose-cfrg-sm4-10

# A.2.3.  SM4-OFB Examples

# A.2.3.1.  Example 1
Plaintext = AAAAAAAABBBBBBBBCCCCCCCCDDDDDDDDEEEEEEEEFFFFFFFFAAAAAAAABBBBBBBB
Key = 0123456789ABCDEFFEDCBA9876543210
IV = 000102030405060708090A0B0C0D0E0F
Ciphertext = AC3236CB861DD316E6413B4E3C7524B71D01ACA2487CA582CBF5463E6698539B

# A.2.3.2.  Example 2
Plaintext = AAAAAAAABBBBBBBBCCCCCCCCDDDDDDDDEEEEEEEEFFFFFFFFAAAAAAAABBBBBBBB
Key = FEDCBA98765432100123456789ABCDEF
IV = 000102030405060708090A0B0C0D0E0F
Ciphertext = 5DCCCD25A84BA16560D7F2658870684933FA16BD5CD9C856CACAA1E101897A97