How the H_p(x) (Hash to a point on the curve), is calculated in Monero?

Question

How the H_p(x) (Hash to a point on the curve), is calculated in Monero?

The reference in [1] state that it calculated directly.

Is it also use keccack?

[1]- Zero to Monero https://getmonero.org/library/Zero-to-Monero-1-0-0.pdf

Answer 1

Hash to point first uses keccak, and then interprets the result as an EC point. The point is multiplied by 8 to ensure that the point is in the group of the base point G. You can see the implementation in the Monero codebase here: https://github.com/monero-project/monero/blob/8f6f674753bae7494e1ee4569004947d47a4e983/src/crypto/crypto.cpp#L481