crypto: public X,Y from fixed private key

[3052]

Proposal Details

I am seeing no way to return the public X,Y from a fixed private key. this creates a fixed private key:

https://pkg.go.dev/crypto/ecdh#Curve.NewPrivateKey

then you can get the public key:

https://pkg.go.dev/crypto/ecdh#PrivateKey.PublicKey

but it stops after that because they X,Y are not available. you can create a private key like this:

https://pkg.go.dev/crypto/ecdsa#GenerateKey

then get X,Y via

1. https://pkg.go.dev/crypto/ecdsa#PrivateKey.PublicKey
2. https://pkg.go.dev/crypto/ecdsa#PublicKey.X
3. https://pkg.go.dev/crypto/ecdsa#PublicKey.Y

but I see no way to create a fixed private key. even if you constructed a deterministic rand:

func GenerateKey(c elliptic.Curve, rand io.Reader) (*PrivateKey, error)

it seems it wouldnt matter:

Note that the returned key does not depend deterministically on the bytes read from rand, and may change between calls and/or between versions.

for prior art, you can do this with Python:

https://pycryptodome.readthedocs.io/en/latest/src/public_key/ecc.html#Crypto.PublicKey.ECC.EccKey

[gabyhelp]

Related Issues

• proposal: crypto/ecdh: allow external curve and key implementations #69863
• crypto/ecdh: new package #52221 (closed)
• proposal: crypto/ed25519: change GenerateKey to return private key only #37431 (closed)

Related Documentation

• Package elliptic > func GenerateKey ¶
• Package ecdh > type Curve ¶ 1.20

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[seankhliao]

the x509 marshal/unmarshal will get you an ecdsa key.

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