(MFC) 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 C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkBinData.h>
#include <CkJwe.h>
#include <CkJsonObject.h>
#include <CkStringBuilder.h>

void ChilkatSample(void)
    {
    CkString strOut;

    // 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.

    bool success;

    // Load a JPG file that will be the JWE payload.
    CkBinData jpgBytes;
    success = jpgBytes.LoadFile("qa_data/jpg/starfish.jpg");
    // Make sure your app checks the success/failure of the call to LoadFile..
    strOut.append("Original JPG size = ");
    strOut.appendInt(jpgBytes.get_NumBytes());
    strOut.append("\r\n");

    CkJwe jwe;

    CkJsonObject jweProtHdr;
    jweProtHdr.AppendString("alg","A128KW");
    jweProtHdr.AppendString("enc","A128CBC-HS256");
    jwe.SetProtectedHeader(jweProtHdr);

    const char *aesWrappingKey = "GawgguFyGrWKav7AX4VKUg";
    jwe.SetWrappingKey(0,aesWrappingKey,"base64url");

    // Encrypt and return the JWE in sbJwe:
    CkStringBuilder sbJwe;
    success = jwe.EncryptBd(jpgBytes,sbJwe);
    if (success != true) {
        strOut.append(jwe.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Show the JWE:
    strOut.append(sbJwe.getAsString());
    strOut.append("\r\n");
    strOut.append("size of JWE: ");
    strOut.appendInt(sbJwe.get_Length());
    strOut.append("\r\n");

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

    CkJwe jwe2;
    success = jwe2.LoadJweSb(sbJwe);
    if (success != true) {
        strOut.append(jwe2.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Set the AES wrap key.
    jwe2.SetWrappingKey(0,aesWrappingKey,"base64url");

    // Decrypt.
    CkBinData jpgOriginal;
    success = jwe2.DecryptBd(0,jpgOriginal);
    if (success != true) {
        strOut.append(jwe2.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("Decrypted JPG size = ");
    strOut.appendInt(jpgOriginal.get_NumBytes());
    strOut.append("\r\n");

    // Save the decrypted JPG to a file.
    success = jpgOriginal.WriteFile("qa_output/jwe_decrypted_starfish.jpg");

    strOut.append("success = ");
    strOut.appendInt(success);
    strOut.append("\r\n");

    // 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


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }