(C++) 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.

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

void ChilkatSample(void)
    {
    // 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: {"alg":"A128KW","enc":"A128CBC-HS256"}
    CkJsonObject jweProtHdr;
    jweProtHdr.AppendString("alg","A128KW");
    jweProtHdr.AppendString("enc","A128CBC-HS256");
    jwe.SetProtectedHeader(jweProtHdr);

    std::cout << "JWE Protected Header: " << jweProtHdr.emit() << "\r\n";
    std::cout << "--" << "\r\n";

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

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

    // Show the JWE we just created:
    std::cout << strJwe << "\r\n";

    // Decrypt the JWE that was just produced.
    // 1) Load the JWE.
    // 2) Set the AES wrapping key.
    // 3) Decrypt.
    CkJwe jwe2;
    success = jwe2.LoadJwe(strJwe);
    if (success != true) {
        std::cout << jwe2.lastErrorText() << "\r\n";
        return;
    }

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

    // Decrypt.
    const char *originalPlaintext = jwe2.decrypt(0,"utf-8");
    if (jwe2.get_LastMethodSuccess() != true) {
        std::cout << jwe2.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "original text: " << "\r\n";
    std::cout << originalPlaintext << "\r\n";

    // ---------------------------------------------------------------------------------
    // 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.

    CkStringBuilder sbJwe;
    sbJwe.Append("eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0.");
    sbJwe.Append("6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ.");
    sbJwe.Append("AxY8DCtDaGlsbGljb3RoZQ.");
    sbJwe.Append("KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY.");
    sbJwe.Append("U0m_YmjN04DJvceFICbCVQ");

    success = jwe2.LoadJweSb(sbJwe);
    if (success != true) {
        std::cout << jwe2.lastErrorText() << "\r\n";
        return;
    }

    jwe2.SetWrappingKey(0,aesWrappingKey,"base64url");

    // Decrypt.
    originalPlaintext = jwe2.decrypt(0,"utf-8");
    if (jwe2.get_LastMethodSuccess() != true) {
        std::cout << jwe2.lastErrorText() << "\r\n";
        return;
    }

    std::cout << originalPlaintext << "\r\n";
    }