uses XceedEncryptionLib_TLB 

var
  xEnc : TXceedEncryption; 
  xRijndael : DXceedRijndaelEncryptionMethod; 
  vaBytesRead : OleVariant;  
begin
  xEnc := TXceedEncryption.Create( self ); 
  xEnc.License( 'your license key' ); 

  xRijndael := CoXceedRijndaelEncryptionMethod.Create();  

  try 
    xRijndael.SetSecretKeyFromPassPhrase( 'This is a weak pass phrase!', 128 ); 

    xEnc. EncryptionMethod := xRijndael; 
    xEnc.ReadFile( 'c:\temp\source.txt', 0, 0, efpEncrypt, true, vaBytesRead ); 

    ShowMessage( 'Encryption successful!' ); 
  except 
    on xErr : Exception do 
      ShowMessage( xErr.Message ); 
  end;  

  xEnc.Free; 
end;