Cryptography, Cryptocurrency, Go, Mathematics, Security.
http://andrea.corbellini.name/images/point-addition-mod-p.png As stated Finite Fields elements can’t be negative. If you want to find -R: ( rx, -ry ) and you know R: ( rx, ry ) you can find -ry by simply computing the modular inverse of ry on the order of the Field: p. We’ll go though adding 2