CryptoSys PKI C# Interface

Our new .NET Class Library for the CryptoSys PKI provides a safer, cleaner interface to .NET methods. These can be used in an almost identical manner in both C# and VB.NET projects. For more details see .NET Class Library Interface.

Doing RSA Encryption and Signing with C#

public static byte[] RsaEncryptBytes(byte[] inputData, string certFile) { StringBuilder sbPublicKey; byte[] block; byte[] outputData; int klen; // 1. Read the public key from the recipient's X.509 certificate sbPublicKey = Rsa.GetPublicKeyFromCert(certFile); if (sbPublicKey.Length == 0) { Console.WriteLine("ERROR reading certificate"); return new byte[0]; } // 2. Make an RSA data block of same length in bytes as key // using EME-PKCS1-v1_5 encoding klen = Rsa.KeyBytes(sbPublicKey.ToString()); if (klen <= 0) { Console.WriteLine("ERROR: invalid public key"); return new byte[0]; } block = Rsa.EncodeMsg(klen, inputData, Rsa.EncodeFor.Encryption); // 3. Encrypt with RSA public key outputData = Rsa.RawPublic(block, sbPublicKey.ToString()); if (outputData.Length == 0) { Console.WriteLine("ERROR: failed to encrypt"); return new byte[0]; } // 4. Clean up Wipe.Data(block); Wipe.String(sbPublicKey); // 5. Output "ciphertext" return outputData; }

byte[] inputData = System.Text.Encoding.Default.GetBytes("Hello world!"); string certFile = "BobRSASignByCarl.cer"; // Output: byte array of "ciphertext" byte[] outputData = RsaEncryptBytes(inputData, certFile); // Display output in hex format Console.WriteLine("ENC={0}", Cnv.ToHex(outputData));

public static byte[] RsaDecryptBytes(byte[] inputData, string priKeyFile, string password) { StringBuilder sbPrivateKey; byte[] block; byte[] outputData; // 1. Read in the private key from the encrypted key file sbPrivateKey = Rsa.ReadEncPrivateKey(priKeyFile, password); if (sbPrivateKey.ToString().Length == 0) { Console.WriteLine("ERROR reading private key file"); return new byte[0]; } // 2. Decrypt with private key block = Rsa.RawPrivate(inputData, sbPrivateKey.ToString()); if (block.Length == 0) { Console.WriteLine("Decryption error"); return new byte[0]; } // 3. Extract the message from the encryption block outputData = Rsa.DecodeMsg(block, Rsa.EncodeFor.Encryption); if (outputData.Length == 0) { Console.WriteLine("Decryption error"); return new byte[0]; } // 4. Clean up - NB should do this on error, too. Wipe.Data(block); Wipe.String(sbPrivateKey); // 5. Output "plaintext" return outputData; }

Download the full source code that demonstrates this encryption and decryption, as well as methods to carry out signing and verification in RsaExample.cs (zipped version, 3 kB). To compile, add this item to a new C# Console Application project and create a reference to diCrSysPKINet.dll. The test certficates and private key files used in the example are in pkiCsharpTestFiles.zip.

References