Silverlight中非对称加密及数字签名RSA算法的实现（二）

2，非对称加密和解密
    私钥加密m（二进制表示）时，首先把m分成长s的数据块 m1, m2 ... mi，其中 2^s <= n, s 尽可能的大。执行如下计算：
        ci = mi ^ d (mod n)
    公钥解密c（二进制表示）时，也需要将c分成长s的数据块c1, c2 ... ci，执行如下计算：
        mi = ci ^ e (mod n)

    在某些情况下，也会使用公钥加密->私钥解密。原理和私钥加密->公钥解密一样。下面是私钥计算和公钥计算的算法。其中利用到了Chew Keong TAN的BigInteger类。.NET Framework 4中提供的BigInteger.ModPow方法好像有问题。 

private static byte[] Compute(byte[] data, RSAPublicKey publicKey, int blockSize)
        {
            //
            // 公钥加密/解密公式为：ci = mi^e ( mod n )            
            // 
            // 先将 m（二进制表示）分成数据块 m1, m2, ..., mi ，然后进行运算。
            //
            BigInteger e = new BigInteger(publicKey.Exponent);
            BigInteger n = new BigInteger(publicKey.Modulus);

            int blockOffset = 0;
            using (MemoryStream stream = new MemoryStream())
            {
                while (blockOffset < data.Length)
                {
                    int blockLen = Math.Min(blockSize, data.Length - blockOffset);
                    byte[] blockData = new byte[blockLen];
                    Buffer.BlockCopy(data, blockOffset, blockData, 0, blockLen);

                    BigInteger mi = new BigInteger(blockData);
                    BigInteger ci = mi.modPow(e, n);//ci = mi^e ( mod n )

                    byte[] block = ci.getBytes();
                    stream.Write(block, 0, block.Length);
                    blockOffset += blockLen;
                }

                return stream.ToArray();
            }
        }

        private static byte[] Compute(byte[] data, RSAPrivateKey privateKey, int blockSize)
        {
            //
            // 私钥加密/解密公式为：mi = ci^d ( mod n )
            // 
            // 先将 c（二进制表示）分成数据块 c1, c2, ..., ci ，然后进行运算。            
            //
            BigInteger d = new BigInteger(privateKey.D);
            BigInteger n = new BigInteger(privateKey.Modulus);

            int blockOffset = 0;

            using (MemoryStream stream = new MemoryStream())
            {
                while (blockOffset < data.Length)
                {
                    int blockLen = Math.Min(blockSize, data.Length - blockOffset);
                    byte[] blockData = new byte[blockLen];
                    Buffer.BlockCopy(data, blockOffset, blockData, 0, blockLen);

                    BigInteger ci = new BigInteger(blockData);
                    BigInteger mi = ci.modPow(d, n);//mi = ci^d ( mod n )

                    byte[] block = mi.getBytes();
                    stream.Write(block, 0, block.Length);
                    blockOffset += blockLen;
                }

                return stream.ToArray();
            }
        }

下面是私钥加密->公钥解密的实现。

public static byte[] Encrypt(byte[] data, RSAPublicKey publicKey)
        {
            if (data == null)
            {
                throw new ArgumentNullException("data");
            }

            if (publicKey == null)
            {
                throw new ArgumentNullException("publicKey");
            }

            int blockSize = publicKey.Modulus.Length - 1;
            return Compute(data, publicKey, blockSize);
        }

        public static byte[] Decrypt(byte[] data, RSAPrivateKey privateKey)
        {
            if (data == null)
            {
                throw new ArgumentNullException("data");
            }

            if (privateKey == null)
            {
                throw new ArgumentNullException("privateKey");
            }

            int blockSize = privateKey.Modulus.Length;
            return Compute(data, privateKey, blockSize);
        }
下面是公钥加密->私钥解密的实现。 
public static byte[] Encrypt(byte[] data, RSAPrivateKey privateKey)
        {
            if (data == null)
            {
                throw new ArgumentNullException("data");
            }

            if (privateKey == null)
            {
                throw new ArgumentNullException("privateKey");
            }

            int blockSize = privateKey.Modulus.Length - 1;
            return Compute(data, privateKey, blockSize);
        }

        public static byte[] Decrypt(byte[] data, RSAPublicKey publicKey)
        {
            if (data == null)
            {
                throw new ArgumentNullException("data");
            }

            if (publicKey == null)
            {
                throw new ArgumentNullException("publicKey");
            }

            int blockSize = publicKey.Modulus.Length;
            return Compute(data, publicKey, blockSize);
        }