Verify a Password against an Argon2 Hash

Demonstrates Crypt2.Argon2VerifyPassword, which verifies a password against a PHC-format Argon2 hash string. The cost parameters are read from the hash string, so none need to be supplied.

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
  crypt: TCrypt2;
  password: string;
  phcHash: string;
  verifyResult: Integer;

begin
  crypt := TCrypt2.Create;

  //  The password should come from a secure source rather than being hard-coded.
  password := 'correct horse battery staple';

  //  A PHC-format Argon2 hash string previously produced by Argon2HashPassword.  All cost options
  //  (variant, version, memory cost, iterations, parallelism, salt, hash length) are read from this
  //  string, so none need to be supplied.
  phcHash := '$argon2id$v=19$m=65536,t=3,p=1$c29tZXJhbmRvbXNhbHQ$3fJ7v1qKcVJ0lHqXjBQZ8mYm3sNTfSPRt0bqDl9kEyM';

  //  Verify the password.  Pass an empty options string when no secret (pepper) or ad was used.
  //  The method returns one of three values:  1 = the password matched, 0 = it did not match, and
  //  -1 = the verification could not be performed (the hash string was invalid or unusable).
  //  Always test for a match with == 1.
  verifyResult := crypt.Argon2VerifyPassword(password,'',phcHash);
  if (verifyResult = 1) then
    begin
      WriteLn('The password is verified.');
    end
  else
    begin
      if (verifyResult = 0) then
        begin
          WriteLn('The password does not match.');
        end
      else
        begin
          WriteLn('The verification could not be performed: ' + crypt.LastErrorText);
        end;
    end;


  crypt.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.