(Delphi DLL) Create JWS Using Private Key on a Smart Card

See more JSON Web Signatures (JWS) Examples

Creates and validates a JSON Web Signature (JWS) using the private key associated with a certificate on a smart card.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, PublicKey, PrivateKey, Jws, Cert, JsonObject;

...

procedure TForm1.Button1Click(Sender: TObject);
var
cert: HCkCert;
success: Boolean;
privKey: HCkPrivateKey;
jwsProtHdr: HCkJsonObject;
jws: HCkJws;
signatureIndex: Integer;
bIncludeBom: Boolean;
payloadStr: PWideChar;
jwsCompact: PWideChar;
jws2: HCkJws;
rsaPubKey: HCkPublicKey;
v: Integer;
joseHeader: HCkJsonObject;

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

// Load the certificate from a smart card.
cert := CkCert_Create();
success := CkCert_LoadFromSmartcard(cert,'');
if (success = False) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

// Note: Chilkat provides many different ways to load a certificate from a smartcard or USB token,
// such as selecting a certificate if the card contains multiple certificates with private keys,
// or working with lower-level PKCS11 or ScMinidriver API's (both of which Chilkat provides).

// If the associated private key was present on the smartcard, then you can simply
// get it from the Chilkat cert object:
privKey := CkCert_ExportPrivateKey(cert);
if (CkCert_getLastMethodSuccess(cert) = False) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

// You can check the key type to make sure it's RSA.
// This will output "rsa" if the key is RSA.
Memo1.Lines.Add('Key type = ' + CkPrivateKey__keyType(privKey));

// Create the JWS Protected Header
jwsProtHdr := CkJsonObject_Create();
CkJsonObject_AppendString(jwsProtHdr,'alg','RS256');

jws := CkJws_Create();

// Set the protected header:
signatureIndex := 0;
CkJws_SetProtectedHeader(jws,signatureIndex,jwsProtHdr);

// Set the RSA key:
CkJws_SetPrivateKey(jws,signatureIndex,privKey);

// Set the payload.
bIncludeBom := False;
payloadStr := 'In our village, folks say God crumbles up the old moon into stars.';
CkJws_SetPayload(jws,payloadStr,'utf-8',bIncludeBom);

// Create the JWS
// By default, the compact serialization is used.
jwsCompact := CkJws__createJws(jws);
if (CkJws_getLastMethodSuccess(jws) <> True) then
  begin
    Memo1.Lines.Add(CkJws__lastErrorText(jws));
    CkPrivateKey_Dispose(privKey);
    Exit;
  end;

Memo1.Lines.Add('JWS: ' + jwsCompact);

// sample output:
// JWS: eyJhbGciOiJQUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.TRWhwRo5dMv9-8OzrInfJTwmUGYgjLfHk8lqF072ND-FmLWEBnUTOpY8oJXp8FdWw2SalbdOeNlrtlJjwk4XK8Ql2iJ_2qMCtxsvLPhKBOqFoAF4aBvTOEDVJDxf0DaBSiydEEtfTVV2iwBcjWabu5J2XieR5y7QZQtuHsn7T3qKBvCcCejN3Y2oqAT3qMHvu1fTms1r_91wBn_K7Wjd9UkZ1n02qQcUHJznR_OF2BgN7_KWIDAF9ZS9keoju2NPpPelO4yxa2XUPnehY3G7dHKoCxUEQR4d2Xc5voqDASTVCDqQS4PVOZdvT3Ein6-SanAlCwbWBbkvT8g6-5PImQ

// Now load the JWS, validate, and recover the original text.
jws2 := CkJws_Create();

// Load the JWS.
success := CkJws_LoadJws(jws2,jwsCompact);

rsaPubKey := CkPrivateKey_GetPublicKey(privKey);
CkPrivateKey_Dispose(privKey);

// Set the RSA public key used for validation.
signatureIndex := 0;
CkJws_SetPublicKey(jws2,signatureIndex,rsaPubKey);
CkPublicKey_Dispose(rsaPubKey);

// Validate the 1st (and only) signature at index 0..
v := CkJws_Validate(jws2,signatureIndex);
if (v < 0) then
  begin
    // Perhaps Chilkat was not unlocked or the trial expired..
    Memo1.Lines.Add('Method call failed for some other reason.');
    Memo1.Lines.Add(CkJws__lastErrorText(jws2));
    Exit;
  end;
if (v = 0) then
  begin
    Memo1.Lines.Add('Invalid signature.  The RSA key was incorrect, the JWS was invalid, or both.');
    Exit;
  end;

// If we get here, the signature was validated..
Memo1.Lines.Add('Signature validated.');

// Recover the original content:
Memo1.Lines.Add(CkJws__getPayload(jws2,'utf-8'));

// Examine the protected header:
joseHeader := CkJws_GetProtectedHeader(jws2,signatureIndex);
if (CkJws_getLastMethodSuccess(jws2) <> True) then
  begin
    Memo1.Lines.Add('No protected header found at the given index.');
    Exit;
  end;
CkJsonObject_putEmitCompact(joseHeader,False);

Memo1.Lines.Add('Protected (JOSE) header:');
Memo1.Lines.Add(CkJsonObject__emit(joseHeader));
CkJsonObject_Dispose(joseHeader);

// Output:

// 	Signature validated.
// 	In our village, folks say God crumbles up the old moon into stars.
// 	Protected (JOSE) header:
// 	{ 
// 	  "alg": "RS256"
// 	}

CkCert_Dispose(cert);
CkJsonObject_Dispose(jwsProtHdr);
CkJws_Dispose(jws);
CkJws_Dispose(jws2);

end;