Save a Public Key as a DER File

Demonstrates the Chilkat PublicKey.SaveDerFile method, which saves the public key as binary DER. The first argument selects the representation (as for GetPem) and the second is the destination path.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: DER is the compact binary encoding many libraries and protocols consume directly. Saving to a .der file is the choice when a consumer wants raw binary rather than Base64 PEM. The first argument picks the traditional (PKCS #1) versus modern (SubjectPublicKeyInfo) structure.

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#include <C_CkPublicKey.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkPublicKey pubKey;
    BOOL preferPkcs1;

    success = FALSE;

    //  Load a public key to export.  LoadFromFile inspects the content, so it accepts DER, PEM, XML,
    //  JWK, and other supported representations.
    pubKey = CkPublicKey_Create();
    success = CkPublicKey_LoadFromFile(pubKey,"qa_data/public.pem");
    if (success == FALSE) {
        printf("%s\n",CkPublicKey_lastErrorText(pubKey));
        CkPublicKey_Dispose(pubKey);
        return;
    }

    //  Save the public key as binary DER.  The 1st argument selects the representation and the 2nd is
    //  the destination path.
    preferPkcs1 = FALSE;
    success = CkPublicKey_SaveDerFile(pubKey,preferPkcs1,"qa_output/public.der");
    if (success == FALSE) {
        printf("%s\n",CkPublicKey_lastErrorText(pubKey));
        CkPublicKey_Dispose(pubKey);
        return;
    }

    printf("Saved.\n");


    CkPublicKey_Dispose(pubKey);

    }