As suggested in https://pkg.go.dev/golang.org/x/crypto/curve25519#ScalarBaseMult,
use X25519 instead of ScalarBaseMult. When using Basepoint, it may employ
some precomputed values, enhancing performance.
Co-authored-by: Wade Simmons <wade@wades.im>
Co-authored-by: Wade Simmons <wadey@slack-corp.com>