如何在 RSA 加密 C#（.net 标准 2.0）中使用公钥

Question

I am developing a .net standard(.net standard 2.0) library.

I have a public key, which is created in server side and I have received it by an api call.

Now I have a string to be encrypted using RSA algorithm. Also, I have to use this public key while encrypting the string which I have.

I went through various samples, but nothing helped.

Tried this one RSA public key encryption in C#

But got error "Operation is not supported on this platform.".

Tried this one, but couldn't find a way to use public key which I have recieved from server.

Here is the latest code which I have tried. I am not sure how and where to use my public key string.

static public byte[] Encryption(byte[] Data, RSAParameters RSAKey, bool DoOAEPPadding)
    {
        try
        {
            byte[] encryptedData;
            using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
            {
                RSA.ImportParameters(RSAKey);
                encryptedData = RSA.Encrypt(Data, DoOAEPPadding);
            }
            return encryptedData;
        }
        catch (CryptographicException e)
        {
            Console.WriteLine(e.Message);
            return null;
        }
    }
    static public byte[] Decryption(byte[] Data, RSAParameters RSAKey, bool DoOAEPPadding)
    {
        try
        {
            byte[] decryptedData;
            using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
            {
                RSA.ImportParameters(RSAKey);
                decryptedData = RSA.Decrypt(Data, DoOAEPPadding);
            }
            return decryptedData;
        }
        catch (CryptographicException e)
        {
            Console.WriteLine(e.ToString());
            return null;
        }
    }

Here i can see RSAKey but it doesn't accept string input.

Can anyone guide me with some samples, through which i can encrypt and decrypt a simple text, with the public which i have.

Thanks, Noorul.

Answer 1

Below you find a full working code that encrypts a string with a RSA public key in XML-encoding and decrypts the ciphertext with a RSA private key (as well in XML encoding). The ciphertext is encoded in base64. Here is a link to an online compiler to see the code running: https://repl.it/@javacrypto/CpcCsharpRsaEncryptionOaepSha1String#main.cs

output:

RSA 2048 encryption OAEP SHA-1 string
plaintext: The quick brown fox jumps over the lazy dog

* * * encrypt the plaintext with the RSA public key * * *
ciphertextBase64: lFZwBN5SnlqAKEYktjjTmDUyIAFA86CDIrOyPeRLVXLIManP6wTUgZ3NBSYynfgwXTmVzhPQL3wZ6kngWIgVbl1sMOSiTt6BOvop5HwEU6ejUOrhgDzuxSnA4e8txNG0X8NZ4kt1bzE42gHlbjxHG+CYawAVYECPMyZ4Jc/n7qH8McsUh3n/KUOB2h5R6DULjf2Qfl4aQHppbEeECNmpSFJFUSu3iGBI7hacHbb+1myyLteS1o3FiBuSVbG+L7h8DEokbhE5yVTwamFF+qM+/HTWeGfE+CGC6Kb8cAucP7Zoov6e+Gr7aFYMvhrWjTvApzMBu5XD0j3JzxQD9OmA8g==

* * * decrypt the ciphertext with the RSA private key * * *
ciphertextReceivedBase64: lFZwBN5SnlqAKEYktjjTmDUyIAFA86CDIrOyPeRLVXLIManP6wTUgZ3NBSYynfgwXTmVzhPQL3wZ6kngWIgVbl1sMOSiTt6BOvop5HwEU6ejUOrhgDzuxSnA4e8txNG0X8NZ4kt1bzE42gHlbjxHG+CYawAVYECPMyZ4Jc/n7qH8McsUh3n/KUOB2h5R6DULjf2Qfl4aQHppbEeECNmpSFJFUSu3iGBI7hacHbb+1myyLteS1o3FiBuSVbG+L7h8DEokbhE5yVTwamFF+qM+/HTWeGfE+CGC6Kb8cAucP7Zoov6e+Gr7aFYMvhrWjTvApzMBu5XD0j3JzxQD9OmA8g==
decryptedData: The quick brown fox jumps over the lazy dog

Security warning : the code uses hard coded RSA [sample] keys for demonstration only. The code has no exception handling and is for educational purpose only.

using System;
using System.Security.Cryptography;
using System.Text;
using System.IO;

class RsaEncryptionOaepSha1 {
    static void Main() {
    Console.WriteLine("RSA 2048 encryption OAEP SHA-1 string");
    string dataToEncryptString = "The quick brown fox jumps over the lazy dog";
    Console.WriteLine("plaintext: " + dataToEncryptString);

    // # # # usually we would load the private and public key from a file or keystore # # #
    // # # # here we use hardcoded keys for demonstration - don't do this in real programs # # #
    string filenamePrivateKeyXml = "privatekey2048.xml";
    string filenamePublicKeyXml = "publickey2048.xml";

        try {
      // encryption
        Console.WriteLine("\n* * * encrypt the plaintext with the RSA public key * * *");
        //string publicKeyLoad = loadRsaPublicKeyPem();
        // use this in production
        string publicKeyLoad = File.ReadAllText(filenamePublicKeyXml);
        byte[] dataToEncrypt = Encoding.UTF8.GetBytes(dataToEncryptString);
        string ciphertextBase64 = Base64Encoding(rsaEncryptionOaepSha1(publicKeyLoad, dataToEncrypt));
        //string ciphertextBase64 = "";
        Console.WriteLine("ciphertextBase64: " + ciphertextBase64);

        // transport the encrypted data to recipient

        // receiving the encrypted data, decryption
        Console.WriteLine("\n* * * decrypt the ciphertext with the RSA private key * * *");
        string ciphertextReceivedBase64 = ciphertextBase64;
        Console.WriteLine("ciphertextReceivedBase64: " + ciphertextReceivedBase64);
        //string privateKeyLoad = loadRsaPrivateKeyPem();
        // use this in production
        string privateKeyLoad = File.ReadAllText(filenamePrivateKeyXml);
        byte[] ciphertextReceived = Base64Decoding(ciphertextReceivedBase64);
        byte[] decryptedtextByte = rsaDecryptionOaepSha1(privateKeyLoad, ciphertextReceived);
        Console.WriteLine("decryptedData: " + Encoding.UTF8.GetString(decryptedtextByte, 0, decryptedtextByte.Length));
        }
        catch(ArgumentNullException) {
            Console.WriteLine("The data was not RSA encrypted");
        }
    }

  public static byte[] rsaEncryptionOaepSha1(string publicKeyXml, byte[] plaintext) {
    RSACryptoServiceProvider RSAalg = new RSACryptoServiceProvider(2048);
        RSAalg.PersistKeyInCsp = false;
        RSAalg.FromXmlString(publicKeyXml);
        return RSAalg.Encrypt(plaintext, true);
  }

  public static byte[] rsaDecryptionOaepSha1(string privateKeyXml, byte[] ciphertext) {
    RSACryptoServiceProvider RSAalg = new RSACryptoServiceProvider(2048);
        RSAalg.PersistKeyInCsp = false;
        RSAalg.FromXmlString(privateKeyXml);
    return RSAalg.Decrypt(ciphertext, true);
  }

  static string Base64Encoding(byte[] input) {
    return Convert.ToBase64String(input);
  }

  static byte[] Base64Decoding(String input) {
    return Convert.FromBase64String(input);
  }

  public static string loadRsaPublicKeyPem() {
    return "<RSAKeyValue><Modulus>8EmWJUZ/Osz4vXtUU2S+0M4BP9+s423gjMjoX+qP1iCnlcRcFWxthQGN2CWSMZwR/vY9V0un/nsIxhZSWOH9iKzqUtZD4jt35jqOTeJ3PCSr48JirVDNLet7hRT37Ovfu5iieMN7ZNpkjeIG/CfT/QQl7R+kO/EnTmL3QjLKQNV/HhEbHS2/44x7PPoHqSqkOvl8GW0qtL39gTLWgAe801/w5PmcQ38CKG0oT2gdJmJqIxNmAEHkatYGHcMDtXRBpOhOSdraFj6SmPyHEmLBishaq7Jm8NPPNK9QcEQ3q+ERa5M6eM72PpF93g2p5cjKgyzzfoIV09Zb/LJ2aW2gQw==</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>";
  }

  public static string loadRsaPrivateKeyPem() {
    return "<RSAKeyValue><Modulus>8EmWJUZ/Osz4vXtUU2S+0M4BP9+s423gjMjoX+qP1iCnlcRcFWxthQGN2CWSMZwR/vY9V0un/nsIxhZSWOH9iKzqUtZD4jt35jqOTeJ3PCSr48JirVDNLet7hRT37Ovfu5iieMN7ZNpkjeIG/CfT/QQl7R+kO/EnTmL3QjLKQNV/HhEbHS2/44x7PPoHqSqkOvl8GW0qtL39gTLWgAe801/w5PmcQ38CKG0oT2gdJmJqIxNmAEHkatYGHcMDtXRBpOhOSdraFj6SmPyHEmLBishaq7Jm8NPPNK9QcEQ3q+ERa5M6eM72PpF93g2p5cjKgyzzfoIV09Zb/LJ2aW2gQw==</Modulus><Exponent>AQAB</Exponent><P>/8atV5DmNxFrxF1PODDjdJPNb9pzNrDF03TiFBZWS4Q+2JazyLGjZzhg5Vv9RJ7VcIjPAbMy2Cy5BUffEFE+8ryKVWfdpPxpPYOwHCJSw4Bqqdj0Pmp/xw928ebrnUoCzdkUqYYpRWx0T7YVRoA9RiBfQiVHhuJBSDPYJPoP34k=</P><Q>8H9wLE5L8raUn4NYYRuUVMa+1k4Q1N3XBixm5cccc/Ja4LVvrnWqmFOmfFgpVd8BcTGaPSsqfA4j/oEQp7tmjZqggVFqiM2mJ2YEv18cY/5kiDUVYR7VWSkpqVOkgiX3lK3UkIngnVMGGFnoIBlfBFF9uo02rZpC5o5zebaDIms=</Q><DP>BPXecL9Pp6u/0kwY+DcCgkVHi67J4zqka4htxgP04nwLF/o8PF0tlRfj0S7qh4UpEIimsxq9lrGvWOne6psYxG5hpGxiQQvgIqBGLxV/U2lPKEIb4oYAOmUTYnefBCrmSQW3v93pOP50dwNKAFcGWTDRiB/e9j+3EmZm/7iVzDk=</DP><DQ>rBWkAC/uLDf01Ma5AJMpahfkCZhGdupdp68x2YzFkTmDSXLJ/P15GhIQ+Lxkp2swrvwdL1OpzKaZnsxfTIXNddmEq8PEBSuRjnNzRjQaLnqjGMtTBvF3G5tWkjClb/MW2q4fgWUG8cusetQqQn2k/YQKAOh2jXXqFOstOZQc9Q0=</DQ><InverseQ>BtiIiTnpBkd6hkqJnHLh6JxBLSxUopFvbhlR37Thw1JN94i65dmtgnjwluvR/OMgzcR8e8uCH2sBn5od78vzgiDXsqITF76rJgeO639ILTA4MO3Mz+O2umrJhrkmgSk8hpRKA+5Mf9aE7dwOzHrc8hbj8J102zyYJIE6pOehrGE=</InverseQ><D>hXGYfOMFzXX/vds8HYQZpISDlSF3NmbTCdyZkIsHjndcGoSOTyeEOxV93MggxIRUSjAeKNjPVzikyr2ixdHbp4fAKnjsAjvcfnOOjBp09WW4QCi3/GCfUh0w39uhRGZKPjiqIj8NzBitN06LaoYD6MPg/CtSXiezGIlFn/Hs+MuEzNFu8PFDj9DhOFhfCgQaIgEEr+IHdnl5HuUVrwTnIBrEzZA/08Q0Gv86qQZctZWoD9hPGzeAC+RSMyGVJw6Ls8zBFf0eysB4spsu4LUom/WnZMdS1ls4eqsAX+7AdqPKBRuUVpr8FNyRM3s8pJUiGns6KFsPThtJGuH6c6KVwQ==</D></RSAKeyValue>";
  }

}