3
If I have secp256k1 keypair that is widely known, like a Bitcoin address, can I convert that into a Ed25519 key pair such that someone could access a .onion address in a deterministic way?
Can a Bitcoin (secp256k1) key be converted to a Ed25519 (Tor v3) key?
Answers
1
The bitcoin key could sign a message containing the onion address. There are several other alternatives but there isn't any way to do this without the key holder producing a message of some kind.
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No you can't convert them since they are defined over different curves.
Thanks. It makes sense now that I think about it because there is no way to get the ECC coordinates from the hashed address alone. – Kristopher Ives – 2019-02-27T04:36:48.123
2Even if you had the full public key, you can't convert it to a ed25519 public key in such a way that the private key can be converted in a compatible manner. The secp256k1 and ed25519 have different structure. – Pieter Wuille – 2019-02-27T07:02:26.643