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

# A.2.4.  SM4-CFB Examples

# A.2.4.1.  Example 1
Plaintext = AAAAAAAABBBBBBBBCCCCCCCCDDDDDDDDEEEEEEEEFFFFFFFFAAAAAAAABBBBBBBB
Key = 0123456789ABCDEFFEDCBA9876543210
IV = 000102030405060708090A0B0C0D0E0F
Ciphertext = AC3236CB861DD316E6413B4E3C7524B769D4C54ED433B9A0346009BEB37B2B3F

# A.2.4.2.  Example 2
Plaintext = AAAAAAAABBBBBBBBCCCCCCCCDDDDDDDDEEEEEEEEFFFFFFFFAAAAAAAABBBBBBBB
Key = FEDCBA98765432100123456789ABCDEF
IV = 000102030405060708090A0B0C0D0E0F
Ciphertext = 5DCCCD25A84BA16560D7F265887068490D9B86FF20C3BFE115FFA02CA6192CC5