Use secp256k1 in Go

Question

I'm trying to use the elliptic curve secp256k1 in Go with the library "crypto/x509". After the key pair generation, I obtain respectively the public key pubKey and the private key privKey. After that, I want to generate a certificate that include the public key, but before I want to store the private key in a .pem file:

keyDer, err := x509.MarshalECPrivateKey(privKey) if err != nil { log.Fatalf("Failed to serialize ECDSA key: %s\n", err) }

but when I try to marshal an EC private key into ASN.1, DER format and to compile the code, I receive an error that said:

Failed to serialize ECDSA key: x509: unknown elliptic curve

In this case it's necessary for me to work with that particular curve, so I cannot change to prime256v1 or ''similar curve''. Is there a solution that permits to add the support for secp256k1 in crypto/x509 library, or another way/suggestion?

@VictorOliveira I'm working with the library: github.com/btcsuite/btcutil/hdkeychain. I'm generating the key as: privKey, err := hdkeychain.NewMaster(seed, &chaincfg.MainNetParams) //EC Private Key sKey, err := privKey.ECPrivKey() and finally as the question's code: keyDer, err := x509.MarshalECPrivateKey(privKey.ToECDSA()) — CipherX
– CipherX, Commented Mar 25, 2018 at 14:27
why not just use the secp256k1 C library instead. You can still compile with cgo. — rny
– rny, Commented Apr 10, 2018 at 3:02
I used this github.com/sour-is/koblitz, then clone the Golang x509 package by starting from x509.ParseCertificate() and resolving all dependencies. Noted: i'm not affiliated in anyway with the lib — trung
– trung, Commented Jul 1, 2019 at 18:01
@trung is there a public repository where your modified x509 package can be found? — Gaëtan Lehmann
– Gaëtan Lehmann, Commented Jun 11, 2020 at 11:57

0xFrenky · Accepted Answer · 2022-04-07 09:02:30Z

6

You can use secp256k1 module by decred/dcrd. It is currently used by btcsuite/btcd repo.

answered Apr 7, 2022 at 9:02

0xFrenky

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Comments

Gilles-Antoine Nys · Accepted Answer · 2020-08-21 04:17:01Z

There is no secp256k1 curve type in go.

How did you created key-pairs?

I faced this problem. In my case, I used the go-ethereum package to create this curve type. So, I used the same package's function to parse the key.

So you have to use same package's specified function to parse the key-pair.

This x509.MarshalECPrivateKey(privKey) will only helps to Marshal go's standard curve type.

be aware that this go-ethereum implementation of secp256k1 is not fully supported without cgo enabled github.com/ethereum/go-ethereum/blob/v1.11.5/crypto/secp256k1/…

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