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Add X25519Kyber768Draft00 experimental HPKE KEM #421

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merged 1 commit into from
Apr 12, 2023
+564 −131
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Add X25519Kyber768Draft00 experimental HPKE KEM #421

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13 changes: 8 additions & 5 deletions hpke/aead.go
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Original file line number Diff line number Diff line change
Expand Up @@ -7,11 +7,14 @@ import (

type encdecContext struct {
// Serialized parameters
suite Suite
exporterSecret []byte
key []byte
baseNonce []byte
sequenceNumber []byte
suite Suite
sharedSecret []byte
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secret []byte
keyScheduleContext []byte
exporterSecret []byte
key []byte
baseNonce []byte
sequenceNumber []byte

// Operational parameters
cipher.AEAD
Expand Down
4 changes: 2 additions & 2 deletions hpke/aead_test.go
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Expand Up @@ -44,12 +44,12 @@ func setupAeadTest() (*sealContext, *openContext, error) {

sealer := &sealContext{
&encdecContext{
suite, nil, nil, baseNonce, make([]byte, Nn), aead, make([]byte, Nn),
suite, nil, nil, nil, nil, nil, baseNonce, make([]byte, Nn), aead, make([]byte, Nn),
},
}
opener := &openContext{
&encdecContext{
suite, nil, nil, baseNonce, make([]byte, Nn), aead, make([]byte, Nn),
suite, nil, nil, nil, nil, nil, baseNonce, make([]byte, Nn), aead, make([]byte, Nn),
},
}
return sealer, opener, nil
Expand Down
82 changes: 35 additions & 47 deletions hpke/algs.go
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@ import (
"github.com/cloudflare/circl/dh/x448"
"github.com/cloudflare/circl/ecc/p384"
"github.com/cloudflare/circl/kem"
"github.com/cloudflare/circl/kem/kyber/kyber768"
"golang.org/x/crypto/chacha20poly1305"
"golang.org/x/crypto/hkdf"
)
Expand All @@ -35,6 +36,9 @@ const (
// KEM_X448_HKDF_SHA512 is a KEM using X448 Diffie-Hellman function and
// HKDF with SHA-512.
KEM_X448_HKDF_SHA512 KEM = 0x21
// KEM_X25519_KYBER768_DRAFT00 is a hybrid KEM built on DHKEM(X25519, HKDF-SHA256)
// and Kyber768Draft00
KEM_X25519_KYBER768_DRAFT00 KEM = 0x30
)

// IsValid returns true if the KEM identifier is supported by the HPKE package.
Expand All @@ -44,7 +48,8 @@ func (k KEM) IsValid() bool {
KEM_P384_HKDF_SHA384,
KEM_P521_HKDF_SHA512,
KEM_X25519_HKDF_SHA256,
KEM_X448_HKDF_SHA512:
KEM_X448_HKDF_SHA512,
KEM_X25519_KYBER768_DRAFT00:
return true
default:
return false
Expand All @@ -65,32 +70,8 @@ func (k KEM) Scheme() kem.AuthScheme {
return dhkemx25519hkdfsha256
case KEM_X448_HKDF_SHA512:
return dhkemx448hkdfsha512
default:
panic(ErrInvalidKEM)
}
}

func (k KEM) validatePublicKey(pk kem.PublicKey) bool {
switch k {
case KEM_P256_HKDF_SHA256, KEM_P384_HKDF_SHA384, KEM_P521_HKDF_SHA512:
pub, ok := pk.(*shortKEMPubKey)
return ok && k == pub.scheme.id && pub.Validate()
case KEM_X25519_HKDF_SHA256, KEM_X448_HKDF_SHA512:
pub, ok := pk.(*xKEMPubKey)
return ok && k == pub.scheme.id && pub.Validate()
default:
panic(ErrInvalidKEM)
}
}

func (k KEM) validatePrivateKey(sk kem.PrivateKey) bool {
switch k {
case KEM_P256_HKDF_SHA256, KEM_P384_HKDF_SHA384, KEM_P521_HKDF_SHA512:
priv, ok := sk.(*shortKEMPrivKey)
return ok && k == priv.scheme.id && priv.Validate()
case KEM_X25519_HKDF_SHA256, KEM_X448_HKDF_SHA512:
priv, ok := sk.(*xKEMPrivKey)
return ok && k == priv.scheme.id && priv.Validate()
case KEM_X25519_KYBER768_DRAFT00:
return hybridkemX25519Kyber768
default:
panic(ErrInvalidKEM)
}
Expand Down Expand Up @@ -243,36 +224,43 @@ func (a AEAD) CipherLen(mLen uint) uint {
var (
dhkemp256hkdfsha256, dhkemp384hkdfsha384, dhkemp521hkdfsha512 shortKEM
dhkemx25519hkdfsha256, dhkemx448hkdfsha512 xKEM
hybridkemX25519Kyber768 hybridKEM
)

func init() {
dhkemp256hkdfsha256.Curve = elliptic.P256()
dhkemp256hkdfsha256.kemBase.id = KEM_P256_HKDF_SHA256
dhkemp256hkdfsha256.kemBase.name = "HPKE_KEM_P256_HKDF_SHA256"
dhkemp256hkdfsha256.kemBase.Hash = crypto.SHA256
dhkemp256hkdfsha256.kemBase.dhKEM = dhkemp256hkdfsha256
dhkemp256hkdfsha256.dhKemBase.id = KEM_P256_HKDF_SHA256
dhkemp256hkdfsha256.dhKemBase.name = "HPKE_KEM_P256_HKDF_SHA256"
dhkemp256hkdfsha256.dhKemBase.Hash = crypto.SHA256
dhkemp256hkdfsha256.dhKemBase.dhKEM = dhkemp256hkdfsha256

dhkemp384hkdfsha384.Curve = p384.P384()
dhkemp384hkdfsha384.kemBase.id = KEM_P384_HKDF_SHA384
dhkemp384hkdfsha384.kemBase.name = "HPKE_KEM_P384_HKDF_SHA384"
dhkemp384hkdfsha384.kemBase.Hash = crypto.SHA384
dhkemp384hkdfsha384.kemBase.dhKEM = dhkemp384hkdfsha384
dhkemp384hkdfsha384.dhKemBase.id = KEM_P384_HKDF_SHA384
dhkemp384hkdfsha384.dhKemBase.name = "HPKE_KEM_P384_HKDF_SHA384"
dhkemp384hkdfsha384.dhKemBase.Hash = crypto.SHA384
dhkemp384hkdfsha384.dhKemBase.dhKEM = dhkemp384hkdfsha384

dhkemp521hkdfsha512.Curve = elliptic.P521()
dhkemp521hkdfsha512.kemBase.id = KEM_P521_HKDF_SHA512
dhkemp521hkdfsha512.kemBase.name = "HPKE_KEM_P521_HKDF_SHA512"
dhkemp521hkdfsha512.kemBase.Hash = crypto.SHA512
dhkemp521hkdfsha512.kemBase.dhKEM = dhkemp521hkdfsha512
dhkemp521hkdfsha512.dhKemBase.id = KEM_P521_HKDF_SHA512
dhkemp521hkdfsha512.dhKemBase.name = "HPKE_KEM_P521_HKDF_SHA512"
dhkemp521hkdfsha512.dhKemBase.Hash = crypto.SHA512
dhkemp521hkdfsha512.dhKemBase.dhKEM = dhkemp521hkdfsha512

dhkemx25519hkdfsha256.size = x25519.Size
dhkemx25519hkdfsha256.kemBase.id = KEM_X25519_HKDF_SHA256
dhkemx25519hkdfsha256.kemBase.name = "HPKE_KEM_X25519_HKDF_SHA256"
dhkemx25519hkdfsha256.kemBase.Hash = crypto.SHA256
dhkemx25519hkdfsha256.kemBase.dhKEM = dhkemx25519hkdfsha256
dhkemx25519hkdfsha256.dhKemBase.id = KEM_X25519_HKDF_SHA256
dhkemx25519hkdfsha256.dhKemBase.name = "HPKE_KEM_X25519_HKDF_SHA256"
dhkemx25519hkdfsha256.dhKemBase.Hash = crypto.SHA256
dhkemx25519hkdfsha256.dhKemBase.dhKEM = dhkemx25519hkdfsha256

dhkemx448hkdfsha512.size = x448.Size
dhkemx448hkdfsha512.kemBase.id = KEM_X448_HKDF_SHA512
dhkemx448hkdfsha512.kemBase.name = "HPKE_KEM_X448_HKDF_SHA512"
dhkemx448hkdfsha512.kemBase.Hash = crypto.SHA512
dhkemx448hkdfsha512.kemBase.dhKEM = dhkemx448hkdfsha512
dhkemx448hkdfsha512.dhKemBase.id = KEM_X448_HKDF_SHA512
dhkemx448hkdfsha512.dhKemBase.name = "HPKE_KEM_X448_HKDF_SHA512"
dhkemx448hkdfsha512.dhKemBase.Hash = crypto.SHA512
dhkemx448hkdfsha512.dhKemBase.dhKEM = dhkemx448hkdfsha512

hybridkemX25519Kyber768.kemBase.id = KEM_X25519_KYBER768_DRAFT00
hybridkemX25519Kyber768.kemBase.name = "HPKE_KEM_X25519_KYBER768_HKDF_SHA256"
hybridkemX25519Kyber768.kemBase.Hash = crypto.SHA256
hybridkemX25519Kyber768.kemA = dhkemx25519hkdfsha256
hybridkemX25519Kyber768.kemB = kyber768.Scheme()
}
26 changes: 1 addition & 25 deletions hpke/hpke.go
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Expand Up @@ -105,10 +105,6 @@ type Sender struct {

// NewSender creates a Sender with knowledge of the receiver's public-key.
func (suite Suite) NewSender(pkR kem.PublicKey, info []byte) (*Sender, error) {
if !suite.kemID.validatePublicKey(pkR) {
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As part of this checking, the validation also checks whether the KEM in the suite is compatible with the KEM key.

The same applies to other checking.

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Let's address that in a separate PR?

return nil, ErrInvalidKEMPublicKey
}

return &Sender{
state: state{Suite: suite, info: info},
pkR: pkR,
Expand All @@ -127,10 +123,6 @@ func (s *Sender) Setup(rnd io.Reader) (enc []byte, seal Sealer, err error) {
func (s *Sender) SetupAuth(rnd io.Reader, skS kem.PrivateKey) (
enc []byte, seal Sealer, err error,
) {
if !s.kemID.validatePrivateKey(skS) {
return nil, nil, ErrInvalidKEMPrivateKey
}

s.modeID = modeAuth
s.state.skS = skS
return s.allSetup(rnd)
Expand All @@ -152,10 +144,6 @@ func (s *Sender) SetupPSK(rnd io.Reader, psk, pskID []byte) (
func (s *Sender) SetupAuthPSK(rnd io.Reader, skS kem.PrivateKey, psk, pskID []byte) (
enc []byte, seal Sealer, err error,
) {
if !s.kemID.validatePrivateKey(skS) {
return nil, nil, ErrInvalidKEMPrivateKey
}

s.modeID = modeAuthPSK
s.state.skS = skS
s.state.psk = psk
Expand All @@ -174,10 +162,6 @@ type Receiver struct {
func (suite Suite) NewReceiver(skR kem.PrivateKey, info []byte) (
*Receiver, error,
) {
if !suite.kemID.validatePrivateKey(skR) {
return nil, ErrInvalidKEMPrivateKey
}

return &Receiver{state: state{Suite: suite, info: info}, skR: skR}, nil
}

Expand All @@ -192,10 +176,6 @@ func (r *Receiver) Setup(enc []byte) (Opener, error) {
// SetupAuth generates a new HPKE context used for Auth Mode encryption.
// SetupAuth takes an encapsulated key and a public key, and returns an Opener.
func (r *Receiver) SetupAuth(enc []byte, pkS kem.PublicKey) (Opener, error) {
if !r.kemID.validatePublicKey(pkS) {
return nil, ErrInvalidKEMPublicKey
}

r.modeID = modeAuth
r.enc = enc
r.state.pkS = pkS
Expand All @@ -219,10 +199,6 @@ func (r *Receiver) SetupPSK(enc, psk, pskID []byte) (Opener, error) {
func (r *Receiver) SetupAuthPSK(
enc, psk, pskID []byte, pkS kem.PublicKey,
) (Opener, error) {
if !r.kemID.validatePublicKey(pkS) {
return nil, ErrInvalidKEMPublicKey
}

r.modeID = modeAuthPSK
r.enc = enc
r.state.psk = psk
Expand All @@ -237,7 +213,7 @@ func (s *Sender) allSetup(rnd io.Reader) ([]byte, Sealer, error) {
if rnd == nil {
rnd = rand.Reader
}
seed := make([]byte, scheme.SeedSize())
seed := make([]byte, scheme.EncapsulationSeedSize())
_, err := io.ReadFull(rnd, seed)
if err != nil {
return nil, nil, err
Expand Down
1 change: 1 addition & 0 deletions hpke/hybrid-x25119-kyber768-test-vectors.json
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