(MFC) JWE using PBES2 Key Wrapping

Demonstrates how to create and decrypt a JWE that using PBES2 key wrapping.

This example demonstrates PBES2 with HMAC SHA-256 and A128KW wrapping. It is also possible to do the following by simply changing the "alg" parameter:

• PBES2 with HMAC SHA-384 and A192KW wrapping
• PBES2 with HMAC SHA-512 and A256KW wrapping

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>
#include <CkPrng.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","PBES2-HS256+A128KW");
    jweProtHdr.AppendString("enc","A128GCM");

    // PBES2 requires two additional parameters:
    // 1) A random salt parameter ("p2s") containing 8 or more bytes in base64url format.
    // 2) An iteration count parameter ("p2c").  A minimum count of 1000 is recommended.
    //    The iteration count is intended to make the PBES2 computation more expensive (time consuming)
    //    to prevent brute-force attacks.
    CkPrng prng;
    jweProtHdr.AppendString("p2s",prng.genRandom(16,"base64url"));
    jweProtHdr.AppendString("p2c","1000");

    strOut.append("JWE Protected Header: ");
    strOut.append(jweProtHdr.emit());
    strOut.append("\r\n");
    strOut.append("--");
    strOut.append("\r\n");

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

    // Set the PBES2 password
    int recipientIndex = 0;
    jwe.SetPassword(recipientIndex,"top secret");

    // 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;
    }

    // Set the PBES2 password
    jwe2.SetPassword(recipientIndex,"top secret");

    // 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:

    // JWE Protected Header: {"alg":"PBES2-HS256+A128KW","enc":"A128GCM","p2s":"z39rTEfRy1T1Yn_D1mZRlg","p2c":"1000"}
    // --
    // eyJhbGciOiJQQkVTMi1IUzI1NitBMTI4S1ciLCJlbmMiOiJBMTI4R0NNIiwicDJzIjoiejM5clRFZlJ5MVQxWW5fRDFtWlJsZyIsInAyYyI6IjEwMDAifQ.koYt6PrFmYwcwdcT7ZcvXHA1d-Xez5h4.luGlbvEnZp-7IsBOj42Yhw.YMTcfLf8Qe4zazozGV2OAu3cUdQ8Kg.rWub47ESWkc6IqZJTvSTmg
    // original text: 
    // Live long and prosper.


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }