Is it possible to evaluate public key sign of bitcoin?
Question
Suppose P is a public key derived from private key -100000. Coordinate of P is (x,y). Here private key is negative. Is it possible to evaluate the sign from the coordinate of P?
Answer 1
A private key of -d is equivalent to a private key of n-d, where n is the secp256k1 curve order. In other words, there is nothing special about such a private key, as it literally just wraps around.
Further more, there is no way to get any information about what number range the private key lies in, just based on the public key. If there, it could be used to break the security of the elliptic curve (and e.g. compute the full private key for a given public key).
So, no.