Org.BouncyCastle.Crypto.Macs.CbcBlockCipherMac.Init C# (CSharp) Method

		public void Init(
            ICipherParameters parameters)
        {
            Reset();

			cipher.Init(true, parameters);
        }

        private int calculateMac(byte[] data, int dataOff, int dataLen, byte[] macBlock)
        {
            IMac cMac = new CbcBlockCipherMac(cipher, parameters.MacSize);

            byte[] nonce = parameters.GetNonce();
            byte[] associatedText = parameters.GetAssociatedText();

            cMac.Init(parameters.Key);

            //
            // build b0
            //
            byte[] b0 = new byte[16];

            if (associatedText != null && associatedText.Length != 0)
            {
                b0[0] |= 0x40;
            }

            b0[0] |= (byte)((((cMac.GetMacSize() - 2) / 2) & 0x7) << 3);

            b0[0] |= (byte)(((15 - nonce.Length) - 1) & 0x7);

            Array.Copy(nonce, 0, b0, 1, nonce.Length);

            int q = dataLen;
            int count = 1;
            while (q > 0)
            {
                b0[b0.Length - count] = (byte)(q & 0xff);
                q >>= 8;
                count++;
            }

            cMac.BlockUpdate(b0, 0, b0.Length);

            //
            // process associated text
            //
            if (associatedText != null)
            {
                int extra;

                if (associatedText.Length < ((1 << 16) - (1 << 8)))
                {
                    cMac.Update((byte)(associatedText.Length >> 8));
                    cMac.Update((byte)associatedText.Length);

                    extra = 2;
                }
                else // can't go any higher than 2^32
                {
                    cMac.Update((byte)0xff);
                    cMac.Update((byte)0xfe);
                    cMac.Update((byte)(associatedText.Length >> 24));
                    cMac.Update((byte)(associatedText.Length >> 16));
                    cMac.Update((byte)(associatedText.Length >> 8));
                    cMac.Update((byte)associatedText.Length);

                    extra = 6;
                }

                cMac.BlockUpdate(associatedText, 0, associatedText.Length);

                extra = (extra + associatedText.Length) % 16;
                if (extra != 0)
                {
                    for (int i = 0; i != 16 - extra; i++)
                    {
                        cMac.Update((byte)0x00);
                    }
                }
            }

            //
            // add the text
            //
            cMac.BlockUpdate(data, dataOff, dataLen);

            return cMac.DoFinal(macBlock, 0);
        }