(PHP 7 >= 7.2.0, PHP 8)
sodium_crypto_scalarmult — Compute a shared secret given a user's secret key and another user's public key
$n, string $p): stringElliptic Curve Diffie-Hellman. Calculates scalar n times point p, on an elliptic curve.
nscalar, which is typically a secret key
ppoint (x-coordinate), which is typically a public key
A 32-byte random string.