A Pseudo-Random Function (PFR) maps an input to an output that is indistinguishable from an element picked uniformly at random from its image set.
In symmetric cryptography, PRFs can for instance be used for as the round function of a Feistel network, or directly as message authentication codes. However, they have their own direct uses in some high level protocols, in particular for some types of MPC.
In this case, the security requirements are relaxed: only weak PRFs are needed, meaning that we do not need to assume that the attacker can pick the plaintext sent to the black box they are trying to distinguish. Instead, those are picked uniformly at random.
STAP Lounge
The STAP Zoo currently collects information about the following list of STAP PRFs: