(MFC) JWE using "dir" Direct use of Shared Symmetric Key

Demonstrates how to create a JWE using the "dir" alg -- which is to directly use a shared symmetric key.

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 <CkJwe.h>
#include <CkJsonObject.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;
    const char *plaintext = "Live long and prosper.";

    CkJwe jwe;

    // First build the JWE Protected Header..
    CkJsonObject jweProtHdr;
    jweProtHdr.AppendString("alg","dir");
    jweProtHdr.AppendString("enc","A128GCM");

    // Don't forget to actually provide the protected header to the JWE object:
    jwe.SetProtectedHeader(jweProtHdr);

    // The JWE is to use 128-bit AES GCM encryption as specified by the "enc" parameter.
    // Given that the "alg" = "dir", we are to directly specify the AES GCM key.
    // (It is assumed that the decrypting side also has knowledge of the direct key to be used..)

    // Our key will be these 16 hex bytes: 000102030405060708090A0B0C0D0E0F

    // The SetWrappingKey method is also used for "dir" direct keys.
    // However, if there are multiple recipients, they must all share the same CEK (Content Encryption Key),
    // which is specified by calling SetWrappingKey with an index of 0.

    int recipientIndex = 0;
    jwe.SetWrappingKey(recipientIndex,"000102030405060708090A0B0C0D0E0F","hex");

    // Encrypt and return the JWE:
    const char *strJwe = jwe.encrypt(plaintext,"utf-8");
    if (jwe.get_LastMethodSuccess() != true) {
        strOut.append(jwe.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Show the JWE we just created:
    strOut.append(strJwe);
    strOut.append("\r\n");

    // Decrypt the JWE.
    CkJwe jwe2;
    success = jwe2.LoadJwe(strJwe);
    if (success != true) {
        strOut.append(jwe2.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    jwe2.SetWrappingKey(0,"000102030405060708090A0B0C0D0E0F","hex");

    // Decrypt.
    const char *originalPlaintext = jwe2.decrypt(0,"utf-8");
    if (jwe2.get_LastMethodSuccess() != true) {
        strOut.append(jwe2.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("original text: ");
    strOut.append("\r\n");
    strOut.append(originalPlaintext);
    strOut.append("\r\n");

    // Sample output:
    // eyJhbGciOiJkaXIiLCJlbmMiOiJBMTI4R0NNIn0..20HX5Huc7f1nQC4pBUtiCQ.axFZIxtZy5j0ifJQUzGXLKIpsBuxJA.eBrOC-NrsreN6JeGuOPk1g
    // original text: 
    // Live long and prosper.


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }