Pascal (Lazarus/Delphi)

Use RSAES-OAEP Padding for Encrypted Email

Demonstrates the Chilkat Email.OaepPadding property, which selects the RSA encryption scheme used when encrypting email. The default is false, which selects RSAES PKCS1-v1_5; setting it to true selects RSAES-OAEP. This affects the RSA key-encryption step used for S/MIME encryption — it does not change the symmetric content-encryption algorithm chosen by Pkcs7CryptAlg. This example enables OAEP padding.

Background: Recall that S/MIME encrypts the message body with a one-time symmetric key, then encrypts that key with RSA. "Padding" is how the key bytes are formatted before RSA is applied. The older PKCS1-v1_5 padding has known theoretical weaknesses, while RSAES-OAEP adds randomness and a hash-based construction that is provably more secure and is the modern recommendation. Both endpoints must agree, so a recipient's software has to support OAEP to read the message.

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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.Email;

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

procedure RunDemo;
var
  email: TEmail;

begin
  //  Demonstrates the Email.OaepPadding property, which selects the RSA encryption scheme
  //  used when encrypting email.  The default is false (RSAES PKCS1-v1_5).  Set it to true
  //  to use RSAES-OAEP.  This affects only the RSA key-encryption step, not the symmetric
  //  content-encryption algorithm selected by Pkcs7CryptAlg.

  email := TEmail.Create;
  email.Subject := 'Encrypted with RSAES-OAEP';
  email.Body := 'This message uses OAEP padding for the RSA key encryption.';

  //  Use RSAES-OAEP instead of the older PKCS1-v1_5 scheme.
  email.OaepPadding := True;

  WriteLn('OaepPadding = ' + email.OaepPadding);


  email.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.