C

Compute JWK Thumbprint for RSA and EC Public Keys

See more ECC Examples

Demonstrates how to compute a JSON Web Key thumbprint for a public key (RSA or ECC).

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

C

#include <C_CkPublicKey.h>
#include <C_CkStringBuilder.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkPublicKey pubKey;
    HCkStringBuilder sb;

    success = FALSE;

    pubKey = CkPublicKey_Create();

    // A public key can be loaded from any format (binary DER, PEM, etc.)
    // This example will load the public keys from JWK format, 
    // and will then compute the JWK thumbprint.

    // First do it for an RSA public key...

    sb = CkStringBuilder_Create();
    CkStringBuilder_Append(sb,"{");
    CkStringBuilder_Append(sb,"\"kty\": \"RSA\",");
    CkStringBuilder_Append(sb,"\"n\": \"0vx7agoebGcQSuuPiLJXZptN9nndrQmbXEps2aiAFbWhM78LhWx4cbbfAAt");
    CkStringBuilder_Append(sb,"VT86zwu1RK7aPFFxuhDR1L6tSoc_BJECPebWKRXjBZCiFV4n3oknjhMstn6");
    CkStringBuilder_Append(sb,"4tZ_2W-5JsGY4Hc5n9yBXArwl93lqt7_RN5w6Cf0h4QyQ5v-65YGjQR0_FD");
    CkStringBuilder_Append(sb,"W2QvzqY368QQMicAtaSqzs8KJZgnYb9c7d0zgdAZHzu6qMQvRL5hajrn1n9");
    CkStringBuilder_Append(sb,"1CbOpbISD08qNLyrdkt-bFTWhAI4vMQFh6WeZu0fM4lFd2NcRwr3XPksINH");
    CkStringBuilder_Append(sb,"aQ-G_xBniIqbw0Ls1jF44-csFCur-kEgU8awapJzKnqDKgw\",");
    CkStringBuilder_Append(sb,"\"e\": \"AQAB\",");
    CkStringBuilder_Append(sb,"\"alg\": \"RS256\",");
    CkStringBuilder_Append(sb,"\"kid\": \"2011-04-29\"");
    CkStringBuilder_Append(sb,"}");

    // The JWK format is automatically detected..
    success = CkPublicKey_LoadFromString(pubKey,CkStringBuilder_getAsString(sb));
    if (success != TRUE) {
        printf("%s\n",CkPublicKey_lastErrorText(pubKey));
        CkPublicKey_Dispose(pubKey);
        CkStringBuilder_Dispose(sb);
        return;
    }

    // Get the JWK thumbprint (using SHA256)
    printf("JWK thumbprint: %s\n",CkPublicKey_getJwkThumbprint(pubKey,"SHA256"));

    // Output:
    // JWK thumbprint: NzbLsXh8uDCcd-6MNwXF4W_7noWXFZAfHkxZsRGC9Xs

    // --------------------------------------------------------------
    // Now let's do an EC public key:
    CkStringBuilder_Clear(sb);
    CkStringBuilder_Append(sb,"{ ");
    CkStringBuilder_Append(sb,"  \"kty\": \"EC\",");
    CkStringBuilder_Append(sb,"  \"crv\": \"P-256\",");
    CkStringBuilder_Append(sb,"  \"x\": \"tDeeYABgKEAbWicYPCEEI8sP4SRIhHKcHDW7VqrB4LA\",");
    CkStringBuilder_Append(sb,"  \"y\": \"J08HOoIZ0rX2Me3bNFZUltfxIk1Hrc8FsLu8VaSxsMI\"");
    CkStringBuilder_Append(sb,"}");

    success = CkPublicKey_LoadFromString(pubKey,CkStringBuilder_getAsString(sb));
    if (success != TRUE) {
        printf("%s\n",CkPublicKey_lastErrorText(pubKey));
        CkPublicKey_Dispose(pubKey);
        CkStringBuilder_Dispose(sb);
        return;
    }

    // Get the JWK thumbprint (using SHA256)
    printf("JWK thumbprint: %s\n",CkPublicKey_getJwkThumbprint(pubKey,"SHA256"));

    // Output:
    // JWK thumbprint: 8fm8079s3nu4FLV_7dVJoJ69A8XCXn7Za2mtaWCnxR4


    CkPublicKey_Dispose(pubKey);
    CkStringBuilder_Dispose(sb);

    }