genericnoauthkem.go raw

   1  package hpke
   2  
   3  // Shim to use generic KEM (kem.Scheme) as HPKE KEM.
   4  
   5  import (
   6  	"github.com/cloudflare/circl/internal/sha3"
   7  	"github.com/cloudflare/circl/kem"
   8  )
   9  
  10  // genericNoAuthKEM wraps a generic KEM (kem.Scheme) to be used as a HPKE KEM.
  11  type genericNoAuthKEM struct {
  12  	kem.Scheme
  13  	name string
  14  }
  15  
  16  func (h genericNoAuthKEM) Name() string { return h.name }
  17  
  18  // HPKE requires DeriveKeyPair() to take any seed larger than the private key
  19  // size, whereas typical KEMs expect a specific seed size. We'll just use
  20  // SHAKE256 to hash it to the right size as in X-Wing.
  21  func (h genericNoAuthKEM) DeriveKeyPair(seed []byte) (kem.PublicKey, kem.PrivateKey) {
  22  	seed2 := make([]byte, h.Scheme.SeedSize())
  23  	hh := sha3.NewShake256()
  24  	_, _ = hh.Write(seed)
  25  	_, _ = hh.Read(seed2)
  26  	return h.Scheme.DeriveKeyPair(seed2)
  27  }
  28