(Delphi DLL) 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 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, Jwe, StringBuilder, JsonObject;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
plaintext: PWideChar;
jwe: HCkJwe;
jweProtHdr: HCkJsonObject;
aesWrappingKey: PWideChar;
strJwe: PWideChar;
jwe2: HCkJwe;
originalPlaintext: PWideChar;
sbJwe: HCkStringBuilder;

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 := CkJwe_Create();

// First build the JWE Protected Header: {"alg":"A128KW","enc":"A128CBC-HS256"}
jweProtHdr := CkJsonObject_Create();
CkJsonObject_AppendString(jweProtHdr,'alg','A128KW');
CkJsonObject_AppendString(jweProtHdr,'enc','A128CBC-HS256');
CkJwe_SetProtectedHeader(jwe,jweProtHdr);

Memo1.Lines.Add('JWE Protected Header: ' + CkJsonObject__emit(jweProtHdr));
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';
CkJwe_SetWrappingKey(jwe,0,aesWrappingKey,'base64url');

// Encrypt and return the JWE:
strJwe := CkJwe__encrypt(jwe,plaintext,'utf-8');
if (CkJwe_getLastMethodSuccess(jwe) <> True) then
  begin
    Memo1.Lines.Add(CkJwe__lastErrorText(jwe));
    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 := CkJwe_Create();
success := CkJwe_LoadJwe(jwe2,strJwe);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkJwe__lastErrorText(jwe2));
    Exit;
  end;
// Set the AES wrap key.
CkJwe_SetWrappingKey(jwe2,0,aesWrappingKey,'base64url');

// Decrypt.
originalPlaintext := CkJwe__decrypt(jwe2,0,'utf-8');
if (CkJwe_getLastMethodSuccess(jwe2) <> True) then
  begin
    Memo1.Lines.Add(CkJwe__lastErrorText(jwe2));
    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 := CkStringBuilder_Create();
CkStringBuilder_Append(sbJwe,'eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.');
CkStringBuilder_Append(sbJwe,'6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ.');
CkStringBuilder_Append(sbJwe,'AxY8DCtDaGlsbGljb3RoZQ.');
CkStringBuilder_Append(sbJwe,'KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.');
CkStringBuilder_Append(sbJwe,'U0m_YmjN04DJvceFICbCVQ');

success := CkJwe_LoadJweSb(jwe2,sbJwe);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkJwe__lastErrorText(jwe2));
    Exit;
  end;

CkJwe_SetWrappingKey(jwe2,0,aesWrappingKey,'base64url');

// Decrypt.
originalPlaintext := CkJwe__decrypt(jwe2,0,'utf-8');
if (CkJwe_getLastMethodSuccess(jwe2) <> True) then
  begin
    Memo1.Lines.Add(CkJwe__lastErrorText(jwe2));
    Exit;
  end;

Memo1.Lines.Add(originalPlaintext);

CkJwe_Dispose(jwe);
CkJsonObject_Dispose(jweProtHdr);
CkJwe_Dispose(jwe2);
CkStringBuilder_Dispose(sbJwe);

end;