Pascal (Lazarus/Delphi)

RSA Encrypt and Decrypt Strings

See more RSA Examples

_LANGUAGE_ sample code to RSA public-key encrypt and decrypt strings using public and private keys. Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.PrivateKey,
  Chilkat.Rsa,
  Chilkat.PublicKey;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  rsa: TRsa;
  privKey: TPrivateKey;
  pubKey: TPublicKey;
  plainText: string;
  rsaEncryptor: TRsa;
  usePrivateKey: Boolean;
  encryptedStr: string;
  rsaDecryptor: TRsa;
  decryptedStr: string;

begin
  success := False;

  //  This example assumes the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  rsa := TRsa.Create;

  //  This example also generates the public and private
  //  keys to be used in the RSA encryption.
  //  Normally, you would generate a key pair once,
  //  and distribute the public key to your partner.
  //  Anything encrypted with the public key can be
  //  decrypted with the private key.  The reverse is 
  //  also true: anything encrypted using the private
  //  key can be decrypted using the public key.

  //  Generate a 2048-bit key.  Chilkat RSA supports
  //  key sizes ranging from 512 bits to 4096 bits.
  privKey := TPrivateKey.Create;
  success := rsa.GenKey(2048,privKey);
  if (success = False) then
    begin
      WriteLn(rsa.LastErrorText);
      Exit;
    end;

  pubKey := TPublicKey.Create;
  privKey.ToPublicKey(pubKey);

  plainText := 'Encrypting and decrypting should be easy!';

  //  Start with a new RSA object to demonstrate that all we
  //  need are the keys previously exported:
  rsaEncryptor := TRsa.Create;

  //  Encrypted output is always binary.  In this case, we want
  //  to encode the encrypted bytes in a printable string.
  //  Our choices are "hex", "base64", "url", "quoted-printable".
  rsaEncryptor.EncodingMode := 'hex';

  //  We'll encrypt with the public key and decrypt with the private
  //  key.
  success := rsaEncryptor.UsePublicKey(pubKey);

  usePrivateKey := False;
  encryptedStr := rsaEncryptor.EncryptStringENC(plainText,usePrivateKey);
  WriteLn(encryptedStr);

  //  Now decrypt:
  rsaDecryptor := TRsa.Create;

  rsaDecryptor.EncodingMode := 'hex';
  success := rsaDecryptor.UsePrivateKey(privKey);

  usePrivateKey := True;
  decryptedStr := rsaDecryptor.DecryptStringENC(encryptedStr,usePrivateKey);

  WriteLn(decryptedStr);


  rsa.Free;
  privKey.Free;
  pubKey.Free;
  rsaEncryptor.Free;
  rsaDecryptor.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.