(C) How to Generate a JSON Web Key (JWK)

Demonstrates how to generate the following types of JSON Web Keys:

• RSA key pair
• EC key pair
• Octet sequence key (HMAC-256)
• 192-bit AES GCM key

Note: This example requires Chilkat v9.5.0.66 or later.

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#include <C_CkRsa.h>
#include <C_CkPrivateKey.h>
#include <C_CkJsonObject.h>
#include <C_CkPrng.h>
#include <C_CkEcc.h>
#include <C_CkCrypt2.h>

void ChilkatSample(void)
    {
    HCkRsa rsa;
    BOOL success;
    HCkPrivateKey rsaKey;
    const char *rsaJwkStr;
    HCkJsonObject json;
    HCkPrng prng;
    HCkEcc ecc;
    HCkPrivateKey ecKey;
    const char *ecJwkStr;
    HCkCrypt2 crypt;
    HCkJsonObject jwkHmac;
    HCkJsonObject jwkAes;

    // This requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // ----------------------------------------------
    // Generate an RSA key pair in JWK format.
    // (Examples for generating other key types are shown below...)
    rsa = CkRsa_Create();
    success = CkRsa_GenerateKey(rsa,2048);
    rsaKey = CkRsa_ExportPrivateKeyObj(rsa);
    rsaJwkStr = CkPrivateKey_getJwk(rsaKey);

    // The string returned is the most compact possible, and therefore it is not
    // very readable.  To pretty-print, load into a JSON object and emit..
    json = CkJsonObject_Create();
    CkJsonObject_putEmitCompact(json,FALSE);
    CkJsonObject_Load(json,rsaJwkStr);
    printf("%s\n",CkJsonObject_emit(json));

    CkPrivateKey_Dispose(rsaKey);

    // Sample RSA JWK:

    // { 
    //   "kty": "RSA",
    //   "n": "6w1Xpof7gKmytJ3yc_yjI5_K3MvVXnBYBDy5Oh2W6Xqu_fOl3W18SjS2AU5xJrTHlB_j84yQjPyXJh_ixjACK4K4dCSYqlLmn3R7QJ84vnHLIEkqwUICqOHdCBjK5xhMrdZxIhuNlJzbARY-3u9RqjsT3HYTjA6JNHUWTYBBRou4gYGm4cJgvX4uexdikqxnze014RmZMaOV_4MR--WL4G8QfNJ2pRBEXQeKyije89H6M5oTSK7KZqFTIqu9hwNtx2oGpGAIcS0Jv5xVl-hDtwXZNwQJaOxMzLw1nwnb2kMliJa67EabQFrQY_xthQNsfzcHJJlpqYiMprW8wRkzmQ",
    //   "e": "AQAB",
    //   "d": "1_bnXMw-SeYhmxAwb19lqVqtMpdaES5ZwHLmoT4EpbsiQ5T1BfENrMSnoaWoEy8w3Kk8cU7qlY-TdOUBIKWFqOKvhY8GciA_Y6zLfgGNSnYVczGmxfBXr0HvKvxUmWZbNbH9OqBkQnKoSmRdGcp7l1Q2mG4o4ZuNdxRJjKXV0_DTrNLUJzst0hsfoZ6mWUrQcn39XGvvLjz9ySS-DYGI1vli3ayx8jVNuw0rU8UXVs9WmPQLvZO_ZDMhoLEeKsdejnNkUNPAUjqxcSOZRojt4BfCmbt-_1slFb0NsoaqnDVZGezd9J9ocxGuyIWHAJu9GGZEcdaFyiDDs_WA1IS_fQ",
    //   "p": "9dU8f6yOklRcpV6ayVMKpyQ6AMuBTF3rZmB498eAvvTkVG1-upm8IkikTVNpPjEalc82Sxuq8oF4N5x1-F33sgVEoCZG-1WFZTn-rnPnXSALES9hqSaVYEwnh61EiY8ckjBVr9jD2nL1JKdbfgVVeo69-9PdjnKYYDVL8eLNPwM",
    //   "q": "9MX2sW0GyaOsZ86AYe3eG2ZgcgKHvhJa573gih5Jvi2e-Nv-L0EVK29_DA7n0Pjm-gl9zVAsGsMMkphJyEF9QgyUlJ-59XLqWnECS5gO6WZdtHrJxVvcO-_AOrLIxeYnYcwhmaVaxs_UEpqGzupKHCWgf4cfXe49lrIsqGKH4jM",
    //   "dp": "IQgj9uvSxGq9gCL0HXUhC1Bc0tqFZyN_i-QOnQybig0R2R5VVvFtTBYCrbk1fPvQHK0ZGIKBN9CZvK8zUsodjDgU_ofmJcNaBz4BsKM2RVcW5Zo-PyJGFAhnj12CxhEKv8Hq4ZP4zROBSQmLy6Uf1TX05S-Up51SSCshJ0FYXs0",
    //   "dq": "RijsMiUfGfL5OvP85pUI4e-xW1yQThHyzpQlZVGTL5jiBVEBhcfw6ndWAj3Pgp2ljyvjTFNboPwhgW93Tpg-8AytFgDGi605sVzNHJ_kPlBiMZY0eYaAFQn-npSaaecziJu7UdAMugneLsruMycCwRij7Ynsmr7sFmLR3B4J9vM",
    //   "qi": "jZE-a1pa8YjflpCSH5oqp1f6f6I6-hpZcLdamLCoAcjVSIPk86gtXtOFES4411-DqYzYIZM6B_g_SRYY6JpKAOuZ40mmMTlnIEoVf8BHiGl3g6bBAiN1yQGXrwXJsg2OYnocyRA-xWNdcMSSFA52SwEdar2Mmw29qVzxtC1QbpA"
    // }

    // ----------------------------------------------
    // Generate an EC P-256 key pair in JWK format

    prng = CkPrng_Create();
    ecc = CkEcc_Create();
    ecKey = CkEcc_GenEccKey(ecc,"P-256",prng);
    if (CkEcc_getLastMethodSuccess(ecc) != TRUE) {
        printf("%s\n",CkEcc_lastErrorText(ecc));
        CkRsa_Dispose(rsa);
        CkJsonObject_Dispose(json);
        CkPrng_Dispose(prng);
        CkEcc_Dispose(ecc);
        return;
    }

    ecJwkStr = CkPrivateKey_getJwk(ecKey);
    CkJsonObject_Load(json,ecJwkStr);
    printf("%s\n",CkJsonObject_emit(json));

    CkPrivateKey_Dispose(ecKey);

    // Sample EC JWK Key:
    // { 
    //   "kty": "EC",
    //   "crv": "P-256",
    //   "x": "tDeeYABgKEAbWicYPCEEI8sP4SRIhHKcHDW7VqrB4LA",
    //   "y": "J08HOoIZ0rX2Me3bNFZUltfxIk1Hrc8FsLu8VaSxsMI",
    //   "d": "-bqt1T0wNAN8sP5ruycQZRVlMlt3V_dSwlJ60xAX5io"
    // }

    // ----------------------------------------------
    // Octet sequence keys are intended for representing secret keys, such as HMAC keys and AES keys.

    // We'll use crypt to generate a random UUID..
    crypt = CkCrypt2_Create();

    // AES and HMAC keys are simply random arrays of bytes
    // For these, we can just build the JSON directly,
    // with the help of the PRNG object.

    jwkHmac = CkJsonObject_Create();
    CkJsonObject_putEmitCompact(jwkHmac,FALSE);

    // Generate a 256-bit HMAK key (32 bytes)
    CkJsonObject_AppendString(jwkHmac,"kty","oct");
    // Give the key an optional ID, which can be anything, even strings as simple as "1", "2", etc.
    CkJsonObject_AppendString(jwkHmac,"kid",CkCrypt2_generateUuid(crypt));
    // Indicate the intended key alg (optional)
    CkJsonObject_AppendString(jwkHmac,"alg","HS256");
    // Generate the actual key bytes
    CkJsonObject_AppendString(jwkHmac,"k",CkPrng_genRandom(prng,32,"base64url"));

    printf("%s\n",CkJsonObject_emit(jwkHmac));

    // Sample HMAC-256 JWK:

    // { 
    //   "kty": "oct",
    //   "kid": "06c2515d-41fb-e436-e405-3abb361f5f7a",
    //   "alg": "HS256",
    //   "k": "wR32w7yiMe5Lhb1vkW2koBpoMxpXTFYuxOYCCIEKjdE"
    // }

    // ----------------------------------------------
    // Now generate a 192-bit (24 byte) key that could be used with AES192GCM

    jwkAes = CkJsonObject_Create();
    CkJsonObject_putEmitCompact(jwkAes,FALSE);

    CkJsonObject_AppendString(jwkAes,"kty","oct");
    CkJsonObject_AppendString(jwkAes,"kid","2");
    CkJsonObject_AppendString(jwkAes,"k",CkPrng_genRandom(prng,24,"base64url"));

    printf("%s\n",CkJsonObject_emit(jwkAes));

    // Sample AES key:
    // { 
    //   "kty": "oct",
    //   "kid": "2",
    //   "k": "akAkq-L_ZTZ6-tEIhDUMtU2ENhsEgL-p"
    // }


    CkRsa_Dispose(rsa);
    CkJsonObject_Dispose(json);
    CkPrng_Dispose(prng);
    CkEcc_Dispose(ecc);
    CkCrypt2_Dispose(crypt);
    CkJsonObject_Dispose(jwkHmac);
    CkJsonObject_Dispose(jwkAes);

    }