How to find the privkey to a "symmetric" point?

[MrFreeDragon]

Let's say that I know the private key to the "compressed" public key point:

PubKey (compressed): 039876090275c25b264eb954d46f6c2af38575e495d741f850640c9555f19ee1f4
Address: 1Q4gKeXEyvQmNc4JuYsuiC8S76c6XEGrwr

Private Key for this pub is: 31a03fb0cd14875e59778fb0c3689ebc13d0870bd2acb7bf479178852e331bec

So, now I want to find the private key for a symmetric point (x-coordinate is the same, but y-coordinate is opposite). In the terms of compressed PubKey the first byte of PubKey "03" should be changed to "02".

So, how to find a PrivateKey for the following PubKey:
PubKey: 029876090275c25b264eb954d46f6c2af38575e495d741f850640c9555f19ee1f4
Address: 19gg34q2FRBTa3CHZqx8NeFTybf9Uk6Cd3

[1714754117]

1714754117

[1714754117]

1714754117

[1714754117]

1714754117

[MrFreeDragon]

Here is the answer:

You should deduct the private key for the 1st point from the order value:

PrivKey for "symmetric" point is:

FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 (order) - 31a03fb0cd14875e59778fb0c3689ebc13d0870bd2acb7bf479178852e331bec (privkey for 1st point) =
ce5fc04f32eb78a1a688704f3c976142a6de55dadc9be87c7840e607a2032555

This is the privkey for "symmetric" point with the address 19gg34q2FRBTa3CHZqx8NeFTybf9Uk6Cd3

PS. Wanted to delete my topic, but could not do it. So, better to post the answer here )

[LoyceMobile]

PS. Wanted to delete my topic, but could not do it.

You can move it to Other > Archival instead.