C

JWE using "dir" Direct use of Shared Symmetric Key

See more JSON Web Encryption (JWE) Examples

Demonstrates how to create a JWE using the "dir" alg -- which is to directly use a shared symmetric key.

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

C

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

void ChilkatSample(void)
    {
    BOOL success;
    const char *plaintext;
    HCkJwe jwe;
    HCkJsonObject jweProtHdr;
    int recipientIndex;
    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.

    // 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","dir");
    CkJsonObject_AppendString(jweProtHdr,"enc","A128GCM");

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

    // The JWE is to use 128-bit AES GCM encryption as specified by the "enc" parameter.
    // Given that the "alg" = "dir", we are to directly specify the AES GCM key.
    // (It is assumed that the decrypting side also has knowledge of the direct key to be used..)

    // Our key will be these 16 hex bytes: 000102030405060708090A0B0C0D0E0F

    // The SetWrappingKey method is also used for "dir" direct keys.
    // However, if there are multiple recipients, they must all share the same CEK (Content Encryption Key),
    // which is specified by calling SetWrappingKey with an index of 0.

    recipientIndex = 0;
    CkJwe_SetWrappingKey(jwe,recipientIndex,"000102030405060708090A0B0C0D0E0F","hex");

    // 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);
        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);
        CkJwe_Dispose(jwe2);
        return;
    }

    CkJwe_SetWrappingKey(jwe2,0,"000102030405060708090A0B0C0D0E0F","hex");

    // 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);
        CkJwe_Dispose(jwe2);
        return;
    }

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

    // Sample output:
    // eyJhbGciOiJkaXIiLCJlbmMiOiJBMTI4R0NNIn0..20HX5Huc7f1nQC4pBUtiCQ.axFZIxtZy5j0ifJQUzGXLKIpsBuxJA.eBrOC-NrsreN6JeGuOPk1g
    // original text: 
    // Live long and prosper.


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

    }