Lazarus Pascal

AES Encrypt and Decrypt a File

_LANGUAGE_ demonstrates how to AES encrypt a file of any size, and then decrypt. Lazarus Pascal

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.Crypt2;

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

procedure RunDemo;
var
  success: Boolean;
  crypt: TCrypt2;
  ivHex: string;
  keyHex: string;
  inFile: string;
  outFile: string;
  decrypt: TCrypt2;

begin
  success := False;

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

  crypt := TCrypt2.Create;

  crypt.CryptAlgorithm := 'aes';

  //  CipherMode may be "ecb" or "cbc"
  crypt.CipherMode := 'cbc';

  //  KeyLength may be 128, 192, 256
  crypt.KeyLength := 256;

  //  The padding scheme determines the contents of the bytes
  //  that are added to pad the result to a multiple of the
  //  encryption algorithm's block size.  AES has a block
  //  size of 16 bytes, so encrypted output is always
  //  a multiple of 16.
  crypt.PaddingScheme := 0;

  //  An initialization vector is required if using CBC mode.
  //  ECB mode does not use an IV.
  //  The length of the IV is equal to the algorithm's block size.
  //  It is NOT equal to the length of the key.
  ivHex := '000102030405060708090A0B0C0D0E0F';
  crypt.SetEncodedIV(ivHex,'hex');

  //  The secret key must equal the size of the key.  For
  //  256-bit encryption, the binary secret key is 32 bytes.
  //  For 128-bit encryption, the binary secret key is 16 bytes.
  keyHex := '000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F';
  crypt.SetEncodedKey(keyHex,'hex');

  //  Encrypt a file, producing the .aes as output.
  //  The input file is unchanged, the output .aes contains the encrypted
  //  contents of the input file.

  //  Note: The .aes output file has no file format.  It is simply a stream
  //  of bytes that resembles random binary data.
  inFile := '/Users/chilkat/testData/pdf/sample.pdf';
  outFile := '/Users/chilkat/testData/p7m/sample.pdf.aes';
  success := crypt.CkEncryptFile(inFile,outFile);
  if (success <> True) then
    begin
      WriteLn(crypt.LastErrorText);
      Exit;
    end;

  //  For demonstration purposes, a different instance of the object will be used
  //  for decryption.
  decrypt := TCrypt2.Create;

  //  All settings must match to be able to decrypt:
  decrypt.CryptAlgorithm := 'aes';
  decrypt.CipherMode := 'cbc';
  decrypt.KeyLength := 256;
  decrypt.PaddingScheme := 0;
  decrypt.SetEncodedIV(ivHex,'hex');
  decrypt.SetEncodedKey(keyHex,'hex');

  //  Decrypt the .aes
  inFile := '/Users/chilkat/testData/p7m/sample.pdf.aes';
  outFile := '/Users/chilkat/testData/pdf/recovered.pdf';
  success := decrypt.CkDecryptFile(inFile,outFile);
  if (success = False) then
    begin
      WriteLn(decrypt.LastErrorText);
      Exit;
    end;

  WriteLn('Success!');


  crypt.Free;
  decrypt.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.