xs/vendor/blitter.com/go/newhope/newhope_simple.go

167 lines
4.2 KiB
Go
Raw Normal View History

// newhope_simple.go - NewHope-Simple interface.
//
// To the extent possible under law, Yawning Angel has waived all copyright
// and related or neighboring rights to newhope, using the Creative
// Commons "CC0" public domain dedication. See LICENSE or
// <http://creativecommons.org/publicdomain/zero/1.0/> for full details.
package newhope
import (
"io"
"golang.org/x/crypto/sha3"
)
const (
// HighBytes is the length of the encoded secret in bytes.
HighBytes = 384
// SendASimpleSize is the length of Alice's NewHope-Simple public key in
// bytes.
SendASimpleSize = PolyBytes + SeedBytes
// SendBSimpleSize is the length of Bob's NewHope-Simple public key in
// bytes.
SendBSimpleSize = PolyBytes + HighBytes
)
func encodeBSimple(r []byte, b *poly, v *poly) {
b.toBytes(r)
v.compress(r[PolyBytes:])
}
func decodeBSimple(b *poly, v *poly, r []byte) {
b.fromBytes(r)
v.decompress(r[PolyBytes:])
}
// PublicKeySimpleAlice is Alice's NewHope-Simple public key.
type PublicKeySimpleAlice struct {
Send [SendASimpleSize]byte
}
// PrivateKeySimpleAlice is Alice's NewHope-Simple private key.
type PrivateKeySimpleAlice struct {
sk poly
}
// Reset clears all sensitive information such that it no longer appears in
// memory.
func (k *PrivateKeySimpleAlice) Reset() {
k.sk.reset()
}
// GenerateKeyPairSimpleAlice returns a NewHope-Simple private/public key pair.
// The private key is generated using the given reader, which must return
// random data. The receiver side of the key exchange (aka "Bob") MUST use
// KeyExchangeSimpleBob() instead of this routine.
func GenerateKeyPairSimpleAlice(rand io.Reader) (*PrivateKeySimpleAlice, *PublicKeySimpleAlice, error) {
var a, e, pk, r poly
var seed, noiseSeed [SeedBytes]byte
if _, err := io.ReadFull(rand, seed[:]); err != nil {
return nil, nil, err
}
seed = sha3.Sum256(seed[:]) // Don't send output of system RNG.
a.uniform(&seed, TorSampling)
if _, err := io.ReadFull(rand, noiseSeed[:]); err != nil {
return nil, nil, err
}
defer memwipe(noiseSeed[:])
privKey := new(PrivateKeySimpleAlice)
privKey.sk.getNoise(&noiseSeed, 0)
privKey.sk.ntt()
e.getNoise(&noiseSeed, 1)
e.ntt()
pubKey := new(PublicKeySimpleAlice)
r.pointwise(&privKey.sk, &a)
pk.add(&e, &r)
encodeA(pubKey.Send[:], &pk, &seed)
return privKey, pubKey, nil
}
// PublicKeySimpleBob is Bob's NewHope-Simple public key.
type PublicKeySimpleBob struct {
Send [SendBSimpleSize]byte
}
// KeyExchangeSimpleBob is the Responder side of the NewHope-Simple key
// exchange. The shared secret and "public key" are generated using the
// given reader, which must return random data.
func KeyExchangeSimpleBob(rand io.Reader, alicePk *PublicKeySimpleAlice) (*PublicKeySimpleBob, []byte, error) {
var pka, a, sp, ep, bp, v, epp, m poly
var seed, noiseSeed [SeedBytes]byte
if _, err := io.ReadFull(rand, noiseSeed[:]); err != nil {
return nil, nil, err
}
defer memwipe(noiseSeed[:])
var sharedKey [SharedSecretSize]byte
if _, err := io.ReadFull(rand, sharedKey[:]); err != nil {
return nil, nil, err
}
defer memwipe(sharedKey[:])
sharedKey = sha3.Sum256(sharedKey[:])
m.fromMsg(sharedKey[:])
decodeA(&pka, &seed, alicePk.Send[:])
a.uniform(&seed, TorSampling)
sp.getNoise(&noiseSeed, 0)
sp.ntt()
ep.getNoise(&noiseSeed, 1)
ep.ntt()
bp.pointwise(&a, &sp)
bp.add(&bp, &ep)
v.pointwise(&pka, &sp)
v.invNtt()
epp.getNoise(&noiseSeed, 2)
v.add(&v, &epp)
v.add(&v, &m) // add key
pubKey := new(PublicKeySimpleBob)
encodeBSimple(pubKey.Send[:], &bp, &v)
mu := sha3.Sum256(sharedKey[:])
// Scrub the sensitive stuff...
sp.reset()
v.reset()
m.reset()
return pubKey, mu[:], nil
}
// KeyExchangeSimpleAlice is the Initiaitor side of the NewHope-Simple key
// exchange. The provided private key is obliterated prior to returning.
func KeyExchangeSimpleAlice(bobPk *PublicKeySimpleBob, aliceSk *PrivateKeySimpleAlice) ([]byte, error) {
var v, bp, k poly
decodeBSimple(&bp, &v, bobPk.Send[:])
k.pointwise(&aliceSk.sk, &bp)
k.invNtt()
k.sub(&k, &v)
var sharedKey [SharedSecretSize]byte
k.toMsg(sharedKey[:])
// mu <- Sha3-256(v')
mu := sha3.Sum256(sharedKey[:])
// Scrub the sensitive stuff...
memwipe(sharedKey[:])
k.reset()
aliceSk.Reset()
return mu[:], nil
}