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PublicKey Cryptography

using System; using System.Security.Cryptography;   class Class1   {     static void Main(string[] args)     {       string dataToSign = "this is a test.";       byte[] data_Bytes = System.Text.Encoding.ASCII.GetBytes( dataToSign );              SHA1Managed sha1 = new SHA1Managed();       byte[] hash_Bytes = sha1.ComputeHash( data_Bytes );            DSACryptoServiceProvider dsa = new DSACryptoServiceProvider();        DSASignatureFormatter sigFormatter = new DSASignatureFormatter(dsa);       sigFormatter.SetHashAlgorithm("SHA1");       byte[] signedHash = sigFormatter.CreateSignature( hash_Bytes );       byte[] remote_SignedHash = signedHash;       byte[] remote_HashedValue = hash_Bytes;       DSASignatureDeformatter sigDeformatter = new DSASignatureDeformatter( dsa );       sigDeformatter.SetHashAlgorithm( "SHA1" );       Console.WriteLine(sigDeformatter.VerifySignature( remote_HashedValue, remote_SignedHash ));       RSACryptoServiceProvider rsa=  new RSACryptoServiceProvider();       byte[] dataToEncrypt = System.Text.Encoding.Unicode.GetBytes( "Encrypt THIS!" );       byte[] encrypted_Bytes;       byte[] decrypted_Bytes;       encrypted_Bytes = rsa.Encrypt( dataToEncrypt, false );       Console.WriteLine("RSA-encrypted data is {0} bytes long.", encrypted_Bytes.Length);       decrypted_Bytes = rsa.Decrypt( encrypted_Bytes, false );       Console.WriteLine("RSA-decrypted string is {0}.", System.Text.Encoding.Unicode.GetString( decrypted_Bytes ));     }   }