Ejemplo n.º 1
2
        public static byte[] CreateSignature(byte[] p_data, ElGamalKeyStruct p_key_struct)
        {
            // define P -1
            BigInteger x_pminusone = p_key_struct.P - 1;
            // create K, which is the random number        
            BigInteger K;
            do
            {
                K = new BigInteger();
                K.genRandomBits(p_key_struct.P.bitCount() - 1, new Random());
            } while (K.gcd(x_pminusone) != 1);

            // compute the values A and B
            BigInteger A = p_key_struct.G.modPow(K, p_key_struct.P);
            BigInteger B = mod(mod(K.modInverse(x_pminusone) * (new BigInteger(p_data) - (p_key_struct.X * (A))), (x_pminusone)), (x_pminusone));
            // copy the bytes from A and B into the result array
            byte[] x_a_bytes = A.getBytes();
            byte[] x_b_bytes = B.getBytes();
            // define the result size
            int x_result_size = (((p_key_struct.P.bitCount() + 7) / 8) * 2);
            // create an array to contain the ciphertext
            byte[] x_result = new byte[x_result_size];
            // populate the arrays
            Array.Copy(x_a_bytes, 0, x_result, x_result_size / 2 - x_a_bytes.Length, x_a_bytes.Length);
            Array.Copy(x_b_bytes, 0, x_result, x_result_size - x_b_bytes.Length, x_b_bytes.Length);
            // return the result array
            return x_result;
        }