anchor.diff:              valid
       end,
       PaddedPlaintext = crypto:block_decrypt(aes_cbc128, EncryptionKey, IV, Ciphertext),
  -    io:format("Padded plaintext: ~w~n", [PaddedPlaintext]),
       pkcs7:unpad(PaddedPlaintext).
   
   encrypt(Plaintext, Key) ->
  
positive.code:     false.
  
  
  decrypt_test() ->
      Key = <<"cw_0x689RpI-jtRR7oE8h_eQsKImvJapLeSbXpwF4e4=">>,
      Token = <<"gAAAAAAdwJ6wAAECAwQFBgcICQoLDA0ODy021cpGVWKZ_eEwCGM4BLLF_5CV9dOPmrhuVUPgJobwOz7JcbmrR64jVmpU4IwqDA==">>,
  
negative.code: decode_key(Key) ->
      KeyBin = base64url:decode(Key),
      <<SigningKey:128/bitstring, EncryptionKey:128/bitstring>> = KeyBin,
      {SigningKey, EncryptionKey}.
  
  generate_key() ->
      base64url:encode(crypto:strong_rand_bytes(256 div 8)).
  
  decrypt(Token, Key) ->
      decrypt(Token, Key, none).
  