(Delphi ActiveX) Validate a JWS Using ECDSA P-521 SHA-512

Validates a JSON Web Signature (JWS) that uses ECDSA P-521 SHA-512

Note: This example requires Chilkat v9.5.0.66 or greater.

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

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Chilkat_TLB;

...

procedure TForm1.Button1Click(Sender: TObject);
var
sbPubKey: TChilkatStringBuilder;
pubKey: TPublicKey;
success: Integer;
jws: TChilkatJws;
signatureIndex: Integer;
sbJws: TChilkatStringBuilder;
v: Integer;
joseHeader: IChilkatJsonObject;

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

// Note: This example requires Chilkat v9.5.0.66 or greater.

// This example takes a JSON signature in compact serialization format,
// and uses an ECDSA public key to validate and recover the protected header and payload.

// We only need a public key for signature validation.  This is the ECDSA public key
// that is used:

//      {"kty":"EC", 
//       "crv":"P-521", 
//       "x":"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk", 
//       "y":"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2" 
//      } 

sbPubKey := TChilkatStringBuilder.Create(Self);
sbPubKey.Append('{"kty":"EC",');
sbPubKey.Append('"crv":"P-521",');
sbPubKey.Append('"x":"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk",');
sbPubKey.Append('"y":"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2"');
sbPubKey.Append('}');

pubKey := TPublicKey.Create(Self);
success := pubKey.LoadFromString(sbPubKey.GetAsString());
if (success <> 1) then
  begin
    Memo1.Lines.Add(pubKey.LastErrorText);
    Exit;
  end;

jws := TChilkatJws.Create(Self);

// Set the ECC public key:
signatureIndex := 0;
jws.SetPublicKey(signatureIndex,pubKey.ControlInterface);

// Load the JWS.
sbJws := TChilkatStringBuilder.Create(Self);
sbJws.Append('eyJhbGciOiJFUzUxMiJ9');
sbJws.Append('.');
sbJws.Append('UGF5bG9hZA');
sbJws.Append('.');
sbJws.Append('AdwMgeerwtHoh-l192l60hp9wAHZFVJbLfD_UxMi70cwnZOYaRI1bKPWROc-mZZq');
sbJws.Append('wqT2SI-KGDKB34XO0aw_7XdtAG8GaSwFKdCAPZgoXD2YBJZCPEX3xKpRwcdOO8Kp');
sbJws.Append('EHwJjyqOgzDO7iKvU8vcnwNrmxYbSW9ERBXukOXolLzeO_Jn');

success := jws.LoadJwsSb(sbJws.ControlInterface);
if (success <> 1) then
  begin
    Memo1.Lines.Add(jws.LastErrorText);
    Exit;
  end;

// Validate the 1st (and only) signature at index 0..
v := jws.Validate(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(jws.LastErrorText);
    Exit;
  end;
if (v = 0) then
  begin
    Memo1.Lines.Add('Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.');
    Exit;
  end;

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

// Recover the original content:
Memo1.Lines.Add('Recovered content:');
Memo1.Lines.Add(jws.GetPayload('utf-8'));
Memo1.Lines.Add('--');

// Examine the protected header:
joseHeader := jws.GetProtectedHeader(signatureIndex);
if (jws.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add('No protected header found at the given index.');
    Exit;
  end;
joseHeader.EmitCompact := 0;

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

// Output:
// (the string "Payload" was the content that was signed.)

// 	Signature validated.
// 	--
// 	Recovered content:
// 	Payload
// 	--
// 	Protected (JOSE) header:
// 	{
// 	  "alg": "ES512"
// 	}
end;