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c++encryptionaescrypto++

Encryption with Crypto++/AES CFB not working

I have a simple console program that should encrypt files with AES CFB algorithm from Crypto++ library. For some reason it is not working. Encoding part:

byte data[16] = { 0x88, 0x44, 0x88, 0x44,
                  0x88, 0x44, 0x88, 0x44,
                  0x88, 0x44, 0x88, 0x44, 
                  0x88, 0x44, 0x88, 0x44 };

byte result[16] = { 0x88, 0x44, 0x88, 0x44,
                    0x88, 0x44, 0x88, 0x44,
                    0x88, 0x44, 0x88, 0x44, 
                    0x88, 0x44, 0x88, 0x44 };

//Sample key
byte key[16] = { 0x88, 0x44, 0x88, 0x44,
                 0x88, 0x44, 0x88, 0x44,
                 0x88, 0x44, 0x88, 0x44, 
                 0x88, 0x44, 0x88, 0x44 };

//Generate random Initialization Vector
byte iv[16];
CryptoPP::AutoSeededRandomPool rnd;
rnd.GenerateBlock(iv, CryptoPP::AES::BLOCKSIZE /*16*/);

//Through VisualStudio debug/watch functionality I have found out that
//Crypto++ randomizer works properly so at this point "iv" contains random values

CryptoPP::CFB_Mode<CryptoPP::AES>::Encryption tmp(key, 16, iv, 1);
tmp.ProcessData(data, result, 16);

The problem is that when this code completes result is supposed to be filled with cyphertext but it just remains filled with px88 and 0x44.

I was guided by this official tutorial: https://www.cryptopp.com/wiki/Advanced_Encryption_Standard

Solution

  • ProcessData is outstring, then instring then length. You've switched the input and output parameters data & result (most API's would put output parameters last in their method declarations, so this could explain the mistake).