(Delphi DLL) JWE with Binary Data

Demonstrates how to create a JWE that contains a binary payload (such as a JPG image).

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, BinData, StringBuilder, JsonObject;

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Boolean;
jpgBytes: HCkBinData;
jwe: HCkJwe;
jweProtHdr: HCkJsonObject;
aesWrappingKey: PWideChar;
sbJwe: HCkStringBuilder;
jwe2: HCkJwe;
jpgOriginal: HCkBinData;

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.

// Load a JPG file that will be the JWE payload.
jpgBytes := CkBinData_Create();
success := CkBinData_LoadFile(jpgBytes,'qa_data/jpg/starfish.jpg');
// Make sure your app checks the success/failure of the call to LoadFile..
Memo1.Lines.Add('Original JPG size = ' + IntToStr(CkBinData_getNumBytes(jpgBytes)));

jwe := CkJwe_Create();

jweProtHdr := CkJsonObject_Create();
CkJsonObject_AppendString(jweProtHdr,'alg','A128KW');
CkJsonObject_AppendString(jweProtHdr,'enc','A128CBC-HS256');
CkJwe_SetProtectedHeader(jwe,jweProtHdr);

aesWrappingKey := 'GawgguFyGrWKav7AX4VKUg';
CkJwe_SetWrappingKey(jwe,0,aesWrappingKey,'base64url');

// Encrypt and return the JWE in sbJwe:
sbJwe := CkStringBuilder_Create();
success := CkJwe_EncryptBd(jwe,jpgBytes,sbJwe);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkJwe__lastErrorText(jwe));
    Exit;
  end;

// Show the JWE:
Memo1.Lines.Add(CkStringBuilder__getAsString(sbJwe));
Memo1.Lines.Add('size of JWE: ' + IntToStr(CkStringBuilder_getLength(sbJwe)));

// ---------------------------------------------------------
// Decrypt to get the original JPG file..

jwe2 := CkJwe_Create();
success := CkJwe_LoadJweSb(jwe2,sbJwe);
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.
jpgOriginal := CkBinData_Create();
success := CkJwe_DecryptBd(jwe2,0,jpgOriginal);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkJwe__lastErrorText(jwe2));
    Exit;
  end;
Memo1.Lines.Add('Decrypted JPG size = ' + IntToStr(CkBinData_getNumBytes(jpgOriginal)));

// Save the decrypted JPG to a file.
success := CkBinData_WriteFile(jpgOriginal,'qa_output/jwe_decrypted_starfish.jpg');

Memo1.Lines.Add('success = ' + IntToStr(Ord(success)));

// The output of this program, when tested, was:
// Original JPG size = 6229
// eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.9YFz_wteV ... 7Et3hKhpxnKEXw
// size of JWE: 8473
// Decrypted JPG size = 6229
// success = True

CkBinData_Dispose(jpgBytes);
CkJwe_Dispose(jwe);
CkJsonObject_Dispose(jweProtHdr);
CkStringBuilder_Dispose(sbJwe);
CkJwe_Dispose(jwe2);
CkBinData_Dispose(jpgOriginal);

end;