Pascal (Lazarus/Delphi)

Compute a Public Key's JWK Thumbprint

Demonstrates the Chilkat PublicKey.GetJwkThumbprint method, which returns the RFC 7638 JWK thumbprint for the public key. The only argument is the hash algorithm (for example sha256).

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: A JWK thumbprint is a canonical hash of the key's public parameters — a compact fingerprint that identifies the key regardless of formatting. It is the standard way to derive a stable key ID (kid) and to check whether two representations are the same key. Chilkat builds the required canonical JSON, hashes it with the named algorithm, and returns the result.

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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.PublicKey;

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

procedure RunDemo;
var
  success: Boolean;
  pubKey: TPublicKey;
  thumbprint: string;

begin
  success := False;

  //  Load a public key to export.  LoadFromFile inspects the content, so it accepts DER, PEM, XML,
  //  JWK, and other supported representations.
  pubKey := TPublicKey.Create;
  success := pubKey.LoadFromFile('qa_data/public.pem');
  if (success = False) then
    begin
      WriteLn(pubKey.LastErrorText);
      Exit;
    end;

  //  Compute the RFC 7638 JWK thumbprint of the public key using the named hash algorithm.  Common
  //  values include "sha256".
  thumbprint := pubKey.GetJwkThumbprint('sha256');
  if (pubKey.LastMethodSuccess = False) then
    begin
      WriteLn(pubKey.LastErrorText);
      Exit;
    end;
  WriteLn('JWK thumbprint: ' + thumbprint);


  pubKey.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.