Hi Cxdinter,

If you define HAVE_ECC_BRAINPOOL then it will enable the Brainpool curves, however you must create the ECC key using wc_ecc_make_key_ex to tell the ECC layer you want to use that curve type:

ecc_key key;
ret = wc_ecc_init(&key);
ret = wc_ecc_make_key_ex(rng, 32, &key, ECC_BRAINPOOLP256R1);

Then you can call wc_SignatureGenerate.

The best way to add defines if not using ./configure is to globally define WOLFSSL_USER_SETTINGS (like in your CFLAGS) and add a new user_settings.h file somewhere in your include path.

There is a good user_settings.h example here:
https://github.com/wolfSSL/wolfssl/blob … settings.h

Also, if you haven't seen it there is a great signature/verify example here:
https://github.com/wolfSSL/wolfssl-exam … /signature
Although its missing the custom ECC curve example above, so I'm going to add that soon.

Thanks,
David Garske, wolfSSL

Hi Cxdinter,

Good find. It looks like the wc_EccPrivateKeyDecode doesn't support importing a custom key and passing the OID to the "wc_ecc_import_private_key" function. I did the implementation for the custom curve ECC support, but missed this import path. I've pushed changes to support this to pull-request 631.
https://github.com/wolfSSL/wolfssl/pull/631

I tested it using the following:

ecc_key key;
byte der[4096];
byte buf[4096];
word32 idx = 0;
FILE* derFile;
size_t sz;

RNG rng;

wc_InitRng(&rng);
wc_ecc_init(&key);

if (wc_ecc_make_key_ex(&rng, 32, &key, ECC_BRAINPOOLP256R1) != 0) {
    printf("error making ecc key\n");
    return -1;
}

/* write private key */
if (wc_EccKeyToDer(&key, der, sizeof(der)) < 0) {
    printf("error in ecc to der\n");
    return -1;
}
printf("writing private key to ecc-key.der\n");
derFile = fopen("ecc-key.der", "w");
if (!derFile) {
    printf("error loading file\n");
    return -1;
}

sz = fwrite(der, 1, 4096, derFile);
fclose(derFile);
wc_ecc_free(&key);


/* open and read from der file */
printf("reading in private key\n");
derFile = fopen("ecc-key.der", "rb");
if (!derFile) {
    printf("error reading from file\n");
    return -1;
}

sz = fread(buf, 1, 4096, derFile);
fclose(derFile);

/* load private ecc key */
printf("storing private key in ecc struct\n");
wc_ecc_init(&key);
if (wc_EccPrivateKeyDecode(buf, &idx, &key, (word32)sz) != 0) {
    printf("error decoding private key\n");
    return -1;
}
wc_ecc_free(&key);

wc_FreeRng(&rng);

Please give it a try and let me know how it goes.

Thanks,
David Garske, wolfSSL

Hi Cxdinter,

The underlying math used for our Ed/Curve implementation is not the same and is highly optimized for that curve. That is the reason Ed/Curve 25519 is not in the ecc_sets table. However I think it would be good to have it in there optionally for those who want to keep the code size down. I'm adding it to our feature list. Thanks for the idea and your reports. Let me know if there is anything else.

Thanks,
David Garske, wolfSSL