Example of Using Twofish Functions

Twofish Encryption and Decryption 

// use of the FCB mode

void TF_sample(void){

   // size of the Twofish algorithm block is equal to 16

   const int tfBlkSize = 16;

   // get the size of the context needed for the encryption/decryption operation

   int ctxSize;

   ippsTwofishGetSize(&ctxSize);

   // and allocate one

   IppsTwofishSpec* pCtx = (IppsTwofishSpec*)( new Ipp8u [ctxSize] );

   // define the key

   // note that the key length may vary from 16 to 32 bytes

   Ipp8u key[] = {0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,

                  0x08,0x09,0x10,0x11,0x12,0x13,0x14,0x15,

                  0x16,0x17};

   // and prepare the context for Twofish usage

   ippsTwofishInit(key,sizeof(key), pCtx);

   // define the message to be encrypted

   Ipp8u ptext[] = {"quick brown fox jupm over lazy dog"};

   // fcb value (bytes)

   const int cfbBlkSize = 2;

   // define an initial vector

   Ipp8u iv[tfBlkSize] = {0xff,0xee,0xdd,0xcc,0xbb,0xaa,0x99,0x88,

                          0x77,0x66,0x55,0x44,0x33,0x22,0x11,0x00}; 

   // allocate enough memory for the ciphertext

   // note that

   // the size of the ciphertext is always multiple of the cfbBlkSize size

   Ipp8u ctext[(sizeof(ptext)+cfbBlkSize-1) &~(cfbBlkSize-1)];

   // encrypt (CFB mode) ptext message

   // pay attention to the 'length' parameter

   // it defines the number of bytes to be encrypted

   ippsTwofishEncryptCFB(ptext, ctext, sizeof(ptext), cfbBlkSize,

                         pCtx,

                         iv,

                         IppsCPPaddingPKCS7);

   // allocate memory for the decrypted message

   Ipp8u rtext[sizeof(ptext)];

   // decrypt (CFB mode) ctext message

// pay attention to the 'length' parameter

   // it defines the number of bytes to be decrypted

ippsTwofishDecryptCFB(ctext, rtext, sizeof(ptext), cfbBlkSize,

                         pCtx,

                         iv,

                         IppsCPPaddingPKCS7);

   delete (Ipp8u*)pCtx;

}