<p>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.</p>

CC BY-SA 4.0
2019-02-27T04:36:48.123Z
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
CC BY-SA 4.0
2019-02-27T07:02:26.643Z
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.
Pieter Wuille
CC BY-SA 4.0
2019-02-27T04:13:52.870Z
2019-02-27T06:06:29.980Z
2019-02-27T06:06:29.980Z
G. Maxwell
<p>No you can't convert them since they are defined over different curves.</p>

CC BY-SA 4.0
2019-02-27T11:22:36.360Z
2019-02-27T11:22:36.360Z
halius
<p>If I have <code>secp256k1</code> keypair that is widely known, like a Bitcoin address, can I convert that into a <code>Ed25519</code> key pair such that someone could access a .onion address in a deterministic way?</p>

<tor><secp256k1>
Can a Bitcoin (secp256k1) key be converted to a Ed25519 (Tor v3) key?
Kristopher Ives
# Can a Bitcoin (secp256k1) key be converted to a Ed25519 (Tor v3) key?

(Asked by: username_0 on 2019-02-27)

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?

**Tags:** tor, secp256k1


---

## 2 answers

### Answer by username_1 on 2019-02-27. Score: 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.

> **Comments:**
> **username_0**: 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.  
> **username_2**: 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.  

---

### Answer by username_3 on 2019-02-27. Score: -1

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


---

