(C) 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.

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#include <C_CkJwe.h>
#include <C_CkJsonObject.h>
#include <C_CkPrng.h>

void ChilkatSample(void)
    {
    BOOL success;
    const char *plaintext;
    HCkJwe jwe;
    HCkJsonObject jweProtHdr;
    HCkPrng prng;
    int recipientIndex;
    const char *strJwe;
    HCkJwe jwe2;
    const char *originalPlaintext;

    // 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.

    plaintext = "Live long and prosper.";

    jwe = CkJwe_Create();

    // First build the JWE Protected Header..
    jweProtHdr = CkJsonObject_Create();
    CkJsonObject_AppendString(jweProtHdr,"alg","PBES2-HS256+A128KW");
    CkJsonObject_AppendString(jweProtHdr,"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.
    prng = CkPrng_Create();
    CkJsonObject_AppendString(jweProtHdr,"p2s",CkPrng_genRandom(prng,16,"base64url"));
    CkJsonObject_AppendString(jweProtHdr,"p2c","1000");

    printf("JWE Protected Header: %s\n",CkJsonObject_emit(jweProtHdr));
    printf("--\n");

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

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

    // Encrypt and return the JWE:
    strJwe = CkJwe_encrypt(jwe,plaintext,"utf-8");
    if (CkJwe_getLastMethodSuccess(jwe) != TRUE) {
        printf("%s\n",CkJwe_lastErrorText(jwe));
        CkJwe_Dispose(jwe);
        CkJsonObject_Dispose(jweProtHdr);
        CkPrng_Dispose(prng);
        return;
    }

    // Show the JWE we just created:
    printf("%s\n",strJwe);

    // Decrypt the JWE.
    jwe2 = CkJwe_Create();
    success = CkJwe_LoadJwe(jwe2,strJwe);
    if (success != TRUE) {
        printf("%s\n",CkJwe_lastErrorText(jwe2));
        CkJwe_Dispose(jwe);
        CkJsonObject_Dispose(jweProtHdr);
        CkPrng_Dispose(prng);
        CkJwe_Dispose(jwe2);
        return;
    }

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

    // Decrypt.
    originalPlaintext = CkJwe_decrypt(jwe2,0,"utf-8");
    if (CkJwe_getLastMethodSuccess(jwe2) != TRUE) {
        printf("%s\n",CkJwe_lastErrorText(jwe2));
        CkJwe_Dispose(jwe);
        CkJsonObject_Dispose(jweProtHdr);
        CkPrng_Dispose(prng);
        CkJwe_Dispose(jwe2);
        return;
    }

    printf("original text: \n");
    printf("%s\n",originalPlaintext);

    // 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.


    CkJwe_Dispose(jwe);
    CkJsonObject_Dispose(jweProtHdr);
    CkPrng_Dispose(prng);
    CkJwe_Dispose(jwe2);

    }