[WP8.1]RSA 使用BouncyCastle 公鑰解密

      寫應用的時候遇到個服務器返回私鑰加密過的數據 ，然后要在客戶端用公鑰解密的需求 ，一直沒找到方法，應用擱置了一個學期，多方搜索，結論就是.net沒有實現公鑰解密的方法，要自己實現，於是硬着頭皮開始看 portable.bouncycastle

      關於RSA的原理,這是我從MSDN盜的圖，鏈接在這https://msdn.microsoft.com/zh-cn/library/system.security.cryptography.rsaparameters.aspx

簡單說就是

密文 = (明文 ^privateExponent) mod modulus

明文 = (密文 ^publicExponent) mod modulus

 

公鑰中含有兩個參數 一個是modulus ，另一個是publicExponent，私鑰中有 modulus和privateExponent兩個參數(當然私鑰中不止這兩個參數，但方法里只用到這兩個，其他不管)

由於拿到的公鑰和私鑰都是PEM格式的，所以要先從PEM格式的公鑰和私鑰中提取這些參數 ，然后進行大數運算就能得出結果

這里要感謝前輩的努力，詳細的解析了PEM文件格式

現在假設假設公鑰和私鑰分別為

　　　　 const string PUBLICKEY =
        　　　　 @"-----BEGIN PUBLIC KEY-----
                MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDpsDr+W45aFHIkvotZaGK/THlF
                FpuZfUtghhWkHAm3H7yvL42J4xHrTr6IeUDCl4eKe6qiIgvYSNoL3u4SERGOeYmV
                1F+cocu9IMGnNoicbh1zVW6e8/iGT3xaYQizJoVuWA/TC/zdds2ihCJfHDBDsouO
                CXecPapyWCGQNsH5sQIDAQAB
                -----END PUBLIC KEY-----";
        const string PRIVATEKEY =
                @"-----BEGIN RSA PRIVATE KEY-----
                MIICXQIBAAKBgQDpsDr+W45aFHIkvotZaGK/THlFFpuZfUtghhWkHAm3H7yvL42J
                4xHrTr6IeUDCl4eKe6qiIgvYSNoL3u4SERGOeYmV1F+cocu9IMGnNoicbh1zVW6e
                8/iGT3xaYQizJoVuWA/TC/zdds2ihCJfHDBDsouOCXecPapyWCGQNsH5sQIDAQAB
                AoGBAM/JbFs4y5WbMncrmjpQj+UrOXVOCeLrvrc/4kQ+zgCvTpWywbaGWiuRo+cz
                cXrVQ6bGGU362e9hr8f4XFViKemDL4SmJbgSDa1K71i+/LnnzF6sjiDBFQ/jA9SK
                4PYrY7a3IkeBQnJmknanykugyQ1xmCjbuh556fOeRPaHnhx1AkEA/flrxJSy1Z+n
                Y1RPgDOeDqyG6MhwU1Jl0yJ1sw3Or4qGRXhjTeGsCrKqV0/ajqdkDEM7FNkqnmsB
                +vPd116J6wJBAOuNY3oOWvy2fQ32mj6XV+S2vcG1osEUaEuWvEgkGqJ9co6100Qp
                j15036AQEEDqbjdqS0ShfeRSwevTJZIap9MCQCeMGDDjKrnDA5CfB0YiQ4FrchJ7
                a6o90WdAHW3FP6LsAh59MZFmC6Ea0xWHdLPz8stKCMAlVNKYPRWztZ6ctQMCQQC8
                iWbeAy+ApvBhhMjg4HJRdpNbwO6MbLEuD3CUrZFEDfTrlU2MeVdv20xC6ZiY3Qtq
                /4FPZZNGdZcSEuc3km5RAkApGkZmWetNwDJMcUJbSBrQMFfrQObqMPBPe+gEniQq
                Ttwu1OULHlmUg9eW31wRI2uiXcFCJMHuro6iOQ1VJ4Qs
                -----END RSA PRIVATE KEY-----";

於是獲取公鑰參數的方法為

 // 獲取modulus和publicExponent
 string publicKey = PUBLICKEY.Replace("-----BEGIN PUBLIC KEY-----", "").Replace("-----END PUBLIC KEY-----", "").Replace("\n", "").Replace("\r", ""); 
 byte[] btPem = Convert.FromBase64String(publicKey);
 int pemModulus = 128, pemPublicExponent = 3;
 byte[] btPemModulus = new byte[128];
 byte[] btPemPublicExponent = new byte[3];
 for (int i = 0; i < pemModulus; i++)
 {
     btPemModulus[i] = btPem[29 + i];
 }
 for (int i = 0; i < pemPublicExponent; i++)
 {
     btPemPublicExponent[i] = btPem[159 + i];
 }

 公鑰解密的方法為

BigInteger biModulus = new BigInteger(1, btPemModulus);
BigInteger biExponent = new BigInteger(1, btPemPublicExponent);
RsaKeyParameters publicParameters = new RsaKeyParameters(false, biModulus, biExponent);
IAsymmetricBlockCipher eng = new Pkcs1Encoding(new RsaEngine());
eng.Init(false, publicParameters);
// 解密已加密的數據
byte[] encryptedData = Convert.FromBase64String(rawData);
encryptedData = eng.ProcessBlock(encryptedData, 0, encryptedData.Length);
string result = Encoding.UTF8.GetString(encryptedData, 0, encryptedData.Length);

公鑰加密的方法為

BigInteger biModulus = new BigInteger(1, btPemModulus);
BigInteger biExponent = new BigInteger(1, btPemPublicExponent);
RsaKeyParameters publicParameters = new RsaKeyParameters(false, biModulus, biExponent);
IAsymmetricBlockCipher eng = new Pkcs1Encoding(new RsaEngine());
eng.Init(true, publicParameters);
// 加密數據
byte[] encryptData = Encoding.UTF8.GetBytes(rawData);
encryptData = eng.ProcessBlock(encryptData, 0, encryptData.Length);
string result = Convert.ToBase64String(encryptData);

私鑰的通過PEM文件格式詳細解析里的圖也可以方便的寫出來，mark下以后寫……(￣o￣) . z Z

順便貼上WP 8.1里自帶的RSA公鑰加密 私鑰解密

　　　　 /// <summary>
        /// WPRT的RSA公鑰加密
        /// </summary>
        /// <param name="rawData">源數據</param>
        /// <returns>加密后的數據</returns>
        public static string PublicEncrypt(string rawData)
        {
            try
            {
                /*將文本轉換成IBuffer*/
                IBuffer bufferRawData = CryptographicBuffer.ConvertStringToBinary(rawData, BinaryStringEncoding.Utf8);

                /*加密算法提供程序*/
                AsymmetricKeyAlgorithmProvider provider = AsymmetricKeyAlgorithmProvider.OpenAlgorithm
                    (AsymmetricAlgorithmNames.RsaPkcs1);

                /*導入公鑰*/
                string PUBLIC_KEY = PUBLICKEY.Replace("-----BEGIN PUBLIC KEY-----", "").Replace("-----END PUBLIC KEY-----", "");
                CryptographicKey publicKey = provider.ImportPublicKey(CryptographicBuffer.DecodeFromBase64String(PUBLIC_KEY));

                //加密
                IBuffer result = CryptographicEngine.Encrypt(publicKey, bufferRawData, null);
                byte[] res;
                CryptographicBuffer.CopyToByteArray(result, out res);
                Debug.WriteLine("WinRT公鑰加密后：" + Convert.ToBase64String(res));
                return Convert.ToBase64String(res);
            }
            catch (Exception e)
            {
                Debug.WriteLine("Encrypt Exception：" + e.StackTrace);
                return rawData;
            }
        }

        /// <summary>
        /// WPRT的RSA私鑰解密
        /// </summary>
        /// <param name="rawData"></param>
        /// <returns></returns>
        public static string PrivateDecrypt(string rawData)
        {
            try
            {
                /*將文本轉換成IBuffer*/
                IBuffer bufferRawData = CryptographicBuffer.ConvertStringToBinary(rawData, BinaryStringEncoding.Utf8);

                /*加密算法提供程序*/
                AsymmetricKeyAlgorithmProvider provider = AsymmetricKeyAlgorithmProvider.OpenAlgorithm
                    (AsymmetricAlgorithmNames.RsaPkcs1);

                /*導入私鑰*/
                string PRIVATE_KEY = PRIVATEKEY.Replace("-----BEGIN RSA PRIVATE KEY-----", "").Replace("-----END RSA PRIVATE KEY-----", "");
                CryptographicKey privateKey = provider.ImportKeyPair(CryptographicBuffer.DecodeFromBase64String(PRIVATE_KEY));

                //解密
                IBuffer result = CryptographicEngine.Decrypt(privateKey, bufferRawData, null);
                byte[] res;
                CryptographicBuffer.CopyToByteArray(result, out res);
                Debug.WriteLine("WinRT私鑰解密后：" + Encoding.UTF8.GetString(res,0,res.Length));
                return Encoding.UTF8.GetString(res,0,res.Length);
            }
            catch (Exception e)
            {
                Debug.WriteLine("Decrypt Exception：" + e.StackTrace);
                return rawData;
            }
        }

 

參考鏈接

PEM文件格式詳細解析

BouncyCastle