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Can I store a public key used to verify a Schnorr signature in PEM format?

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Razvan Marian

I want to ask if there is any way to store a Schnorr signature key in PEM format, or any other standardized format.

And, if possible, I would like to know if that's possible to be done in C language; here's my code so far:

EC_KEY *key = EC_KEY_new();
EC_KEY_set_group(*key, group);
EC_KEY_set_private_key(*key, *a);
EC_KEY_set_public_key(*key, *Q);
...
FILE* fout2 = fopen("pub.key", "wb");
PEM_write_EC_PUBKEY(fout2, Key);
fclose(fout2);

which generates the following public key in PEM format:

-----BEGIN PUBLIC KEY-----
MFYwEAYHKoZIzj0CAQYFK4EEAAoDQgAE6F0upHIXEB8DIEYIBOt+Ps/m3GErnhWy
D35+HMDogZhgrQ0r3Bs4Dm0lIgTKYUU/Mg997FStJx4IrmNqeH5zwQ==
-----END PUBLIC KEY-----

I tried to implement a way of storing Schnorr keys using the EC_KEY structure from openssl. I would like to know if there is any other way or if what i did is correct. Thanks :)

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Maarten Bodewes avatar
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Maarten Bodewes
It looks to me that Schnorr uses the exact same key generation as the related ECDSA. As your key is encoded as bog standard [X.509 EC public key](https://lapo.it/asn1js/#MFYwEAYHKoZIzj0CAQYFK4EEAAoDQgAE6F0upHIXEB8DIEYIBOt-Ps_m3GErnhWyD35-HMDogZhgrQ0r3Bs4Dm0lIgTKYUU_Mg997FStJx4IrmNqeH5zwQ) using the named secp256k1 Koblitz curve, I would assume that this is correct.
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Maarten Bodewes avatar
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Maarten Bodewes
PS Didn't answer because I didn't do any practical work with Schnorr sigs. Please always [edit] additional info into questions instead of posting a hard to read comment.
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