anchor.diff:  
   -define(i32(Int), (Int bsr 24) band 255, (Int bsr 16) band 255, (Int bsr 8) band 255, Int band 255).
   
  --define(BLOCK_CIPHER_AES, aes_cfb128).
  +-define(BLOCK_CIPHER_AES(Key), case size(iolist_to_binary(Key)) of
  +                                   128 -> aes_128_cfb128;
  +                                   192 -> aes_192_cfb128;
  +                                   256 -> aes_256_cfb128
  +                               end).
  +
   -define(BLOCK_CIPHER_DES, des_cbc).
   
   
  
positive.code:     Salt = MsgPrivParams,
      IV = list_to_binary([?i32(EngineBoots), ?i32(EngineTime) | Salt]),
      %% Whatabout errors here???  E.g. not a mulitple of 8!
      Data = binary_to_list(crypto:crypto_one_time(?BLOCK_CIPHER_AES, 
                                                   AesKey, IV, EncData, false)),
      Data2 = snmp_pdus:strip_encrypted_scoped_pdu_data(Data),
      {ok, Data2}.
  
negative.code:     AesKey = PrivKey,
      Salt = SaltFun(),
      IV = list_to_binary([?i32(EngineBoots), ?i32(EngineTime) | Salt]),
      EncData = crypto:crypto_one_time(?BLOCK_CIPHER_AES(AesKey), 
                                       AesKey, IV, Data, true),
      {ok, binary_to_list(EncData), Salt}.
  
  