Exportation of ECC Keys

[yuanxun6844]

I have two questions one question related to the exportation of ECC keys:

1. Alternatively, is Is it possible to export (and import) ECC public keys as a bytestring of length 33, as is done by Bitcoin Core and other programs?

https://en.bitcoin.it/wiki/Elliptic_Curve_Digital_Signature_Algorithm

It would seem that someone has brought this matter up before, or a related issue, but I do not understand the final result, whether or not it was implemented:

#34

Thanks for your help.

[karel-m]

Use the following:

ecc_get_key(buf, &buflen, PK_PUBLIC|PK_COMPRESSED, &key);

To load the exported key you need to use the following sequence:

ltc_ecc_curve *cu;
ecc_key pubkey;
ecc_get_curve("SECP256K1", &cu); /* bitcoin curve */
ecc_set_dp(cu, &pubkey);
ecc_set_key(buf, buflen, PK_PUBLIC, &pubkey);

IMPORTANT NOTICE: the API above is currently only in develop branch (and is expected to be part of libtomcrypt 1.19.x series)

[karel-m]

UPDATE: we have renamed some of the functions recently in develop branch, now you should use:

ltc_ecc_curve *cu;
ecc_key pubkey;
ecc_find_curve("SECP256K1", &cu); /* bitcoin curve */
ecc_set_curve(cu, &pubkey);
ecc_set_key(buf, buflen, PK_PUBLIC, &pubkey);

Unless you have more questions I will close this issue on 13 July.

[yuanxun6844]

Thanks. You have been most helpful.