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?


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.

  • 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. Feb 27 '19 at 4:36
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    Even 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. Feb 27 '19 at 7:02

No you can't convert them since they are defined over different curves.

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