(Delphi ActiveX) JWE using AES Key Wrap and AES_128_CBC_HMAC_SHA_256

This example duplicates the example A.3 in RFC 7516 for JSON Web Encryption (JWE).

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
success: Integer;
plaintext: WideString;
jwe: TChilkatJwe;
jweProtHdr: TChilkatJsonObject;
aesWrappingKey: WideString;
strJwe: WideString;
jwe2: TChilkatJwe;
originalPlaintext: WideString;
sbJwe: TChilkatStringBuilder;

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.

plaintext := 'Live long and prosper.';

jwe := TChilkatJwe.Create(Self);

// First build the JWE Protected Header: {"alg":"A128KW","enc":"A128CBC-HS256"}
jweProtHdr := TChilkatJsonObject.Create(Self);
jweProtHdr.AppendString('alg','A128KW');
jweProtHdr.AppendString('enc','A128CBC-HS256');
jwe.SetProtectedHeader(jweProtHdr.ControlInterface);

Memo1.Lines.Add('JWE Protected Header: ' + jweProtHdr.Emit());
Memo1.Lines.Add('--');

// The example A.3 in RFC 7516 uses the following 128-bit AES key,
// specified in JWK (JSON Web Key) format:
//      {"kty":"oct",
//       "k":"GawgguFyGrWKav7AX4VKUg"
//      }
// This is just a way of saying: The key type ("kty") is 
// a bunch of octets ("k") in base64url encoding.
// We can simply set the AES wrapping key like this:
aesWrappingKey := 'GawgguFyGrWKav7AX4VKUg';
jwe.SetWrappingKey(0,aesWrappingKey,'base64url');

// Encrypt and return the JWE:
strJwe := jwe.Encrypt(plaintext,'utf-8');
if (jwe.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(jwe.LastErrorText);
    Exit;
  end;

// Show the JWE we just created:
Memo1.Lines.Add(strJwe);

// Decrypt the JWE that was just produced.
// 1) Load the JWE.
// 2) Set the AES wrapping key.
// 3) Decrypt.
jwe2 := TChilkatJwe.Create(Self);
success := jwe2.LoadJwe(strJwe);
if (success <> 1) then
  begin
    Memo1.Lines.Add(jwe2.LastErrorText);
    Exit;
  end;
// Set the AES wrap key.
jwe2.SetWrappingKey(0,aesWrappingKey,'base64url');

// Decrypt.
originalPlaintext := jwe2.Decrypt(0,'utf-8');
if (jwe2.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(jwe2.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add('original text: ');
Memo1.Lines.Add(originalPlaintext);

// ---------------------------------------------------------------------------------
// It should also be possible to decrypt the JWE as shown in RFC 7516, Appendix A.3.7
// because it was produced using the same AES Wrap key.

sbJwe := TChilkatStringBuilder.Create(Self);
sbJwe.Append('eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.');
sbJwe.Append('6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ.');
sbJwe.Append('AxY8DCtDaGlsbGljb3RoZQ.');
sbJwe.Append('KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.');
sbJwe.Append('U0m_YmjN04DJvceFICbCVQ');

success := jwe2.LoadJweSb(sbJwe.ControlInterface);
if (success <> 1) then
  begin
    Memo1.Lines.Add(jwe2.LastErrorText);
    Exit;
  end;

jwe2.SetWrappingKey(0,aesWrappingKey,'base64url');

// Decrypt.
originalPlaintext := jwe2.Decrypt(0,'utf-8');
if (jwe2.LastMethodSuccess <> 1) then
  begin
    Memo1.Lines.Add(jwe2.LastErrorText);
    Exit;
  end;

Memo1.Lines.Add(originalPlaintext);
end;