コード例 #1
0
        private byte[] ProcessDecrypt(byte[] byteInput, string password)
        {
            if (password.Length != blockSize)
            {
                throw new Exception("Password is not 128bit long");
            }

            var result = new List <byte>();
            //We will divide the byteInput into Block of 16 chars
            var blockIteration   = (int)Math.Ceiling((byteInput.Length * 1.0) / blockSize);
            var currentByteBlock = new byte[4, 4];
            var cbcBlock         = new byte[4, 4];

            BlockFill(cbcBlock, 0);

            var substitute = new Substitution();
            var addKey     = new AddKey(substitute, password);
            var mixColumn  = new MixColumns();
            var shiftRow   = new ShiftRow();

            for (var blockCount = 0; blockCount < blockIteration; blockCount++)
            {
                var blockStart = blockCount * blockSize;
                var cipherCBC  = new byte[4, 4];
                //COnvert to a blockArray of 4x4
                for (int i = 0; i < 4; i++)
                {
                    for (int j = 0; j < 4; j++)
                    {
                        currentByteBlock[j, i] = byteInput[blockStart + i * 4 + j];
                        cipherCBC[j, i]        = currentByteBlock[j, i];
                    }
                }

                LogEngine.LogBytes(currentByteBlock, "Current Block");

                addKey.AddRoundKey(Nr, currentByteBlock);
                shiftRow.InvByteShift(currentByteBlock);
                substitute.InvByteSub(currentByteBlock);

                for (int rnd = Nr - 1; rnd > 0; rnd--)
                {
                    addKey.AddRoundKey(rnd, currentByteBlock);
                    mixColumn.InvApplyColumn(currentByteBlock);
                    shiftRow.InvByteShift(currentByteBlock);
                    substitute.InvByteSub(currentByteBlock);
                }
                addKey.AddRoundKey(0, currentByteBlock);


                for (int i = 0; i < 4; i++)
                {
                    for (int j = 0; j < 4; j++)
                    {
                        result.Add((byte)(cbcBlock[j, i] ^ currentByteBlock[j, i]));
                    }
                }
                //Copy this stage Cypher as next stage CBC
                BlockCopy(cipherCBC, cbcBlock);
            }
            addKey.Dispose();
            return(result.ToArray());
        }