C

JWE using A256GCMKW

See more JSON Web Encryption (JWE) Examples

This example demonstrates creating a JCE with AES GCM key wrap. C

#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;
    const char *aesWrappingKey;
    const char *strJwe;
    HCkJwe jwe2;
    const char *originalPlaintext;

    success = FALSE;

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

    plaintext = "My text to enrypt";

    jwe = CkJwe_Create();

    // First build the JWE Protected Header: 

    //         {
    //             "alg": "A256GCMKW",
    //             "kid": "18ec08e1-bfa9-4d95-b205-2b4dd1d4321d",
    //             "tag": "kfPduVQ3T3H6vnewt--ksw",
    //             "iv": "KkYT0GX_2jHlfqN_",
    //             "enc": "A128CBC-HS256"
    //         }

    jweProtHdr = CkJsonObject_Create();
    CkJsonObject_AppendString(jweProtHdr,"alg","A256GCMKW");
    // kid is optional
    CkJsonObject_AppendString(jweProtHdr,"kid","18ec08e1-bfa9-4d95-b205-2b4dd1d4321d");
    // tag is optional
    CkJsonObject_AppendString(jweProtHdr,"tag","kfPduVQ3T3H6vnewt--ksw");
    CkJsonObject_AppendString(jweProtHdr,"enc","A256GCM");
    // the iv should be 16 random chars.
    prng = CkPrng_Create();
    CkJsonObject_AppendString(jweProtHdr,"iv",CkPrng_randomString(prng,16,TRUE,TRUE,TRUE));
    CkJwe_SetProtectedHeader(jwe,jweProtHdr);

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

    // Given that we have 256-bit AES, our key should be 32 bytes.
    // The ascii string here is 32 bytes, therefore the 2nd arg is "ascii" to use these
    // ascii chars directly as the key.
    aesWrappingKey = "2baf4f730f5e4542b428593ef9cceb0e";
    CkJwe_SetWrappingKey(jwe,0,aesWrappingKey,"ascii");

    // 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 that was just produced.
    // 1) Load the JWE.
    // 2) Set the AES wrapping key.
    // 3) Decrypt.
    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 AES wrap key.  Important to use "ascii"
    CkJwe_SetWrappingKey(jwe2,0,aesWrappingKey,"ascii");

    // 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);


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

    }