Function hpke::SetupPSKS

pub fn SetupPSKS(
    config: HPKEConfig, 
    pkR: &HpkePublicKey, 
    info: &Info, 
    psk: &Psk, 
    psk_id: &PskId, 
    randomness: Randomness
) -> SenderContextResult

Authentication using a Pre-Shared Key - Sender

This variant extends the base mechanism by allowing the recipient to authenticate that the sender possessed a given PSK. The PSK also improves confidentiality guarantees in certain adversary models, as described in the security properties. We assume that both parties have been provisioned with both the PSK value psk and another byte string psk_id that is used to identify which PSK should be used. The primary difference from the base case is that the psk and psk_id values are used as ikm inputs to the KDF (instead of using the empty string). The PSK MUST have at least 32 bytes of entropy and SHOULD be of length Nh bytes or longer. See the PSK Recommendations for a more detailed discussion.

def SetupPSKS(pkR, info, psk, psk_id):
  shared_secret, enc = Encap(pkR)
  return enc, KeyScheduleS(mode_psk, shared_secret, info, psk, psk_id)