C# RSA加密、解密

C# RSA加密、解密不受加密内容长度限制，自适应加、解密。

 public class RSAHelper
    {
        private readonly static int[] KeySizes = { 512, 1024, 2048, 8192 };
        /// 

        /// 生成密钥
        /// 私钥
        /// 公钥
        /// 密钥长度：512,1024,2048，4096，8192
        /// 
        public static void Generator(out string PrivateKey, out string PublicKey, int KeySize = 2048)
        {
            if (!KeySizes.Any(t => t == KeySize))
                KeySize = 2048;

            using RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(KeySize);
            //将RSA算法的私钥导出到字符串PrivateKey中 参数为true表示导出私钥 true 表示同时包含 RSA 公钥和私钥；false 表示仅包含公钥。
            PrivateKey = rsa.ToXmlString(true);
            // 将RSA算法的公钥导出到字符串PublicKey中 参数为false表示不导出私钥 true 表示同时包含 RSA 公钥和私钥；false 表示仅包含公钥。
            PublicKey = rsa.ToXmlString(false); 
        }
        /// 

        /// RSA加密 将公钥导入到RSA对象中，准备加密
        /// 待加密的字节数不能超过密钥的长度值除以 8 再减去 11（即：RSACryptoServiceProvider.KeySize / 8 - 11），
        /// 而加密后得到密文的字节数，正好是密钥的长度值除以 8（即：RSACryptoServiceProvider.KeySize / 8）。
        /// 
        /// 公钥
        /// 待加密的字符串
        public static string RSAEncrypt(string PublicKey, string encryptstring)
        {
            using RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            byte[] data = (new UnicodeEncoding()).GetBytes(encryptstring); //要加密的数据
            rsa.FromXmlString(PublicKey);
            int bufferSize = (rsa.KeySize >> 3) - 11;
            string result = string.Empty;
            if (data.Length > bufferSize)
                result = RSAEncryptLong(rsa, data, bufferSize);
            else
                result = RSAEncryptNormal(rsa, data);
            return result;
        }
        private static string RSAEncryptLong(RSACryptoServiceProvider rsa, byte[] data, int bufferSize)
        {
            byte[] buffer = new byte[bufferSize];
            using MemoryStream msInput = new MemoryStream(data);
            using MemoryStream msOutput = new MemoryStream();
            int readLen = msInput.Read(buffer, 0, bufferSize);
            while (readLen > 0)
            {
                byte[] dataToEnc = new byte[readLen];
                Array.Copy(buffer, 0, dataToEnc, 0, readLen);
                byte[] encData = rsa.Encrypt(dataToEnc, false);
                msOutput.Write(encData, 0, encData.Length);
                readLen = msInput.Read(buffer, 0, bufferSize);
            }
            byte[] result = msOutput.ToArray();    //得到加密结果
            return ByteSToBase64String(result);
        }
        private static string RSAEncryptNormal(RSACryptoServiceProvider rsa, byte[] data)
        {
            byte[] encrypt = rsa.Encrypt(data, false);
            return ByteSToBase64String(encrypt);
        }
        private static string ByteSToBase64String(byte[] encrypt)
        {
            return Convert.ToBase64String(encrypt);
        }
        /// 

        /// RSA解密 将私钥导入RSA中，准备解密
        /// 
        /// 私钥
        /// 待解密的字符串
        public static string RSADecrypt(string PrivateKey, string decryptstring)
        {
            using RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            byte[] dataEnc = Convert.FromBase64String(decryptstring);   //加载密文
            rsa.FromXmlString(PrivateKey);
            int keySize = rsa.KeySize >> 3;
            string result = string.Empty;
            if (dataEnc.Length > keySize)
                result = RSADecryptLong(rsa, dataEnc, keySize);
            else
                result = RSADecryptNormal(rsa, dataEnc);
            return result;
        }
        private static string RSADecryptNormal(RSACryptoServiceProvider rsa, byte[] dataEnc)
        {
            byte[] DypherTextBArray = rsa.Decrypt(dataEnc, false);
            return (new UnicodeEncoding()).GetString(DypherTextBArray);
        }
        private static string RSADecryptLong(RSACryptoServiceProvider rsa, byte[] dataEnc, int keySize)
        {
            byte[] buffer = new byte[keySize];
            using MemoryStream msInput = new MemoryStream(dataEnc);
            using MemoryStream msOutput = new MemoryStream();
            int readLen = msInput.Read(buffer, 0, keySize);
            while (readLen > 0)
            {
                byte[] dataToDec = new byte[readLen];
                Array.Copy(buffer, 0, dataToDec, 0, readLen);
                byte[] decData = rsa.Decrypt(dataToDec, false);
                msOutput.Write(decData, 0, decData.Length);
                readLen = msInput.Read(buffer, 0, keySize);
            }
            byte[] result = msOutput.ToArray();    //得到解密结果
            return (new UnicodeEncoding()).GetString(result);
        }
    }