RSA 非对称加密与解密

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        private static string Encrypt(string msg, string publickey)
        {
            ASCIIEncoding enc = new ASCIIEncoding();
            byte[] bytes = enc.GetBytes(msg);
            int blockSize = 0;
            RSACryptoServiceProvider crypt = new RSACryptoServiceProvider();
            crypt.FromXmlString(publickey);
            if (crypt.KeySize == 1024)
                blockSize = 16;
            else
                blockSize = 8;

MemoryStream ms = new MemoryStream();

            byte[] rawblock, encryblock;
            for (int i = 0; i < bytes.Length; i += blockSize)
            {
                if ((bytes.Length - i) > blockSize)
                    rawblock = new byte[blockSize];
                else
                    rawblock = new byte[bytes.Length - i];
                Buffer.BlockCopy(bytes, i, rawblock, 0, rawblock.Length);
                encryblock = crypt.Encrypt(rawblock, false);
                ms.Write(encryblock, 0, encryblock.Length);
            }

            ms.Position = 0;
            byte[] decode = new byte[ms.Length];
            ms.Read(decode, 0, (int)ms.Length);

            string decodeinfo = Convert.ToBase64String(decode);
            ms.Close();
            return decodeinfo;

        }
        private static string Decrypt(string msg, string privatekey)
        {
            RSACryptoServiceProvider crypt = new RSACryptoServiceProvider();
            crypt.FromXmlString(privatekey);

ASCIIEncoding enc = new ASCIIEncoding();
byte[] bytes = Convert.FromBase64String(msg);

            MemoryStream ms = new MemoryStream();
            int keySize = crypt.KeySize / 8;
            byte[] rawblock, decryptblock;
            for (int i = 0; i < bytes.Length; i += keySize)
            {
                if ((bytes.Length - i) > keySize)
                {
                    rawblock = new byte[keySize];
                }
                else
                { rawblock = new byte[bytes.Length - i]; }

                Buffer.BlockCopy(bytes, i, rawblock, 0, rawblock.Length);
                decryptblock = crypt.Decrypt(rawblock, false);
                ms.Write(decryptblock, 0, decryptblock.Length);
            }
            ms.Position = 0;
            byte[] decode = new byte[ms.Length];
            ms.Read(decode, 0, (int)ms.Length);

            string text = enc.GetString(decode);
            ms.Close();
            return text;

}