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package hpke
// Shim to use generic KEM (kem.Scheme) as HPKE KEM.
import (
"github.com/cloudflare/circl/internal/sha3"
"github.com/cloudflare/circl/kem"
)
// genericNoAuthKEM wraps a generic KEM (kem.Scheme) to be used as a HPKE KEM.
type genericNoAuthKEM struct {
kem.Scheme
name string
}
func (h genericNoAuthKEM) Name() string { return h.name }
// HPKE requires DeriveKeyPair() to take any seed larger than the private key
// size, whereas typical KEMs expect a specific seed size. We'll just use
// SHAKE256 to hash it to the right size as in X-Wing.
func (h genericNoAuthKEM) DeriveKeyPair(seed []byte) (kem.PublicKey, kem.PrivateKey) {
seed2 := make([]byte, h.Scheme.SeedSize())
hh := sha3.NewShake256()
_, _ = hh.Write(seed)
_, _ = hh.Read(seed2)
return h.Scheme.DeriveKeyPair(seed2)
}
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