How to use a manual private RSA key for encryption in C#?

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I am trying to encrypt a string using RSA algorithm by using the C # built in library
System.Net.Cryptograhy.RSACryptoServiceProvider.

Suppose I have a private key(e.g):

`  -- -- - BEGIN RSA PRIVATE KEY-- -- -
  MIICXQIBAAKBgQCFf3jKXbhn2GOiCzvAxLTmZ34BdFQyNDKt / 7 B3qQ1thmSPG / NK
nrYG8OIHhDqIsGkT1YcEOQKEHPhgmtGj78Fxrv3AEi56VsYfJUTOJn9GTmqPrpk /
  zscIiD5HkWzx8JfOQS5uPHWwGmQpYftDod82nYinlwuZdAVOcz3 + 7 dShlQIDAQAB
AoGAT2sCJQGUTtMAkso0Bf3 / 0 IIJCDx4SlWbQMA37zf28Q1ejXSHTAEXMRHkpawY
VnD8UfxZkj2ILag + atovlWNwpJ + Qgw4 + t3KvPXEQB1LtMDa0q1fA + I3qU / 5 uiOCq
07 y1IWfhJ6UsfhXYV5gOmADeVrwnuGz6YUIBLQ6at3ebHgECQQDPo + 0 UUFC9z6ZX
x2a6UNIFZB9YPmxy599GMjOQOf3tEYH + qn6tYz9oZu7cWrQzkoEJ7Uw7xQsqXADU
ekfaL2f1AkEApJb6G4 + zB8gCWQy6DrqiK4Y6d1CN3s67uuZXMcpQEuju9jNBHwAj
g8zdwNAf98dksRyt7XICROrxv5i7mvFvIQJAPau5eaQVJxsqk720xDfG + TTwnlwE
B + jYhtfYOskOoz / k9UecUlE8 / vw7i5UhGoQz8UfasZHnrBAhavpapvIXlQJBAIPE
q2 + tV / N + 2 QJaAgsQuAyIZf5n62zZrcov5tbh1cGN4uIQnq4m + kfmmBJpjW5dn + t7
vnM + tzpdrjVqHagqaoECQQCAZl + BLRqEQa9cKH5lpJ4k9L + 3 sX4LQjuwNkFyZTr /
  K6Tw5lZv4eBDWtlYToEL3mtgLR7BKEled5cHCZ6pr1nm
  -- -- - END RSA PRIVATE KEY-- -- -`

And I want to use this private key to encrypt the string.

I have seen most of the examples on internet like these

C#

`string data = "ABC";

RSACryptoServiceProvider crypto = new RSACryptoServiceProvider();

string cipherText = Encrypt(data, rsaCryptoServiceProvider.ExportParameters(false));

public static string Encrypt(string data, RSAParameters key) {

    using(var rsa = new RSACryptoServiceProvider()) {
        rsa.FromXmlString(PrivateKey);
        rsa.ImportParameters(key);
        var byteData = Encoding.UTF8.GetBytes(data);
        var encryptData = rsa.Encrypt(byteData, false);
        return Convert.ToBase64String(encryptData);
        }
    }`

But in this method I am not using the Private Key provided.

Can anyone help in encryption using the provided private key ?

I am expecting to get the proper ciphered text from my private key.

Thank You in Advance.Any help is appreciated.

What I have tried:

I have tried this

C#

`string data = "ABC";

RSACryptoServiceProvider crypto = new RSACryptoServiceProvider();

string cipherText = Encrypt(data, rsaCryptoServiceProvider.ExportParameters(false));

public static string Encrypt(string data, RSAParameters key) {

    using(var rsa = new RSACryptoServiceProvider()) {
        
        rsa.ImportParameters(key);
        var byteData = Encoding.UTF8.GetBytes(data);
        var encryptData = rsa.Encrypt(byteData, false);
        return Convert.ToBase64String(encryptData);
        }
    }`

Posted 31-Mar-23 1:41am

kartik sharma Mar2023

Updated 31-Mar-23 7:35am

PIEBALDconsult

v2

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Comments

Richard MacCutchan 1-Apr-23 4:14am

The RSA implementation uses the public key for encryption. The private key is used for decryption.

kartik sharma Mar2023 2-Apr-23 14:23pm

Would you please explain how to use that?
Thanks for replying btw.

Richard MacCutchan 2-Apr-23 15:01pm

You need tp explain exactly what you are trying to do, and where this data came from. As I said, the private key is not used for encryption.

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OriginalGriff · Answer 1 · 2023-03-31T01:50:00

Solution 1

Try starting here: RSA Private Key Encryption[^]

Posted 31-Mar-23 1:50am

OriginalGriff

Nani Nagendra · Answer 2 · 2024-01-02T22:56:00

public string GetEncryptValue(long connectionNumber)
       {

           long creditCardNumber = (connectionNumber);
           string publicKey = ConfigSettings.GetMobikwickEncrypKey();
           string encryptedCreditCard = EncryptWithRSA(creditCardNumber, publicKey);



           byte[] encryptedBytes = Convert.FromBase64String(encryptedCreditCard);
           string decryptedData = Encoding.UTF8.GetString(encryptedBytes);

           return encryptedCreditCard;
       }

static string EncryptWithRSA(long dataToEncrypt, string publicKey)
       {
           try
           {

               RSAParameters rsaParameters = GetRSAParametersFromKey(publicKey);

               using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
               {

                   //byte[] x509Key = ExportX509Key(rsaParameters);
                   //rsa.ImportCspBlob(x509Key);
                   rsa.ImportParameters(rsaParameters);
                   byte[] dataBytes = BitConverter.GetBytes(dataToEncrypt);
                   Array.Resize(ref dataBytes, 8);
                   byte[] encryptedData = rsa.Encrypt(dataBytes, false);
                   string encryptedBase64 = Convert.ToBase64String(encryptedData);


                   return encryptedBase64;
               }
           }
           catch (Exception ex)
           {
               Console.WriteLine("Encryption failed: " + ex.Message);
           }

           return "";
       }

static RSAParameters GetRSAParametersFromKey(string publicKeyValue)
      {
          byte[] modulusBytes = Encoding.UTF8.GetBytes(publicKeyValue);
          Array.Resize(ref modulusBytes, 256);
          byte[] exponentBytes = { 1, 0, 1 };

          RSAParameters rsaParameters = new RSAParameters
          {
              Modulus = modulusBytes,
              Exponent = exponentBytes
          };

          return rsaParameters;
      }