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crypto/mlkem: swap order of return values of Encapsulate

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Per FIPS 203 (https://csrc.nist.gov/pubs/fips/203/final), the order of return values should be sharedKey, ciphertext. This commit simply swaps those return values and updates any consumers of the Encapsulate() method to respect the new order.

Fixes #70950

Change-Id: I2a0d605e3baf7fe69510d60d3d35bbac18f883c9
Reviewed-on: https://go-review.googlesource.com/c/go/+/638376
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Austin Clements <austin@google.com>
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
This commit is contained in:
Alec Bakholdin 2024-12-22 20:36:59 -05:00 • committed by Gopher Robot
parent 772f024c61
commit cce75da30b
7 changed files with 25 additions and 25 deletions
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2
src/crypto/internal/fips140/mlkem/cast.go
View file

@ -40,7 +40,7 @@ func init() {
dk := &DecapsulationKey768{}
kemKeyGen(dk, d, z)
ek := dk.EncapsulationKey()
c, Ke := ek.EncapsulateInternal(m)
Ke, c := ek.EncapsulateInternal(m)
Kd, err := dk.Decapsulate(c)
if err != nil {
return err

12
src/crypto/internal/fips140/mlkem/mlkem1024.go
View file

@ -189,7 +189,7 @@ func kemKeyGen1024(dk *DecapsulationKey1024, d, z *[32]byte) {
// the first operational use (if not exported before the first use)."
func kemPCT1024(dk *DecapsulationKey1024) error {
ek := dk.EncapsulationKey()
c, K := ek.Encapsulate()
K, c := ek.Encapsulate()
K1, err := dk.Decapsulate(c)
if err != nil {
return err
@ -204,13 +204,13 @@ func kemPCT1024(dk *DecapsulationKey1024) error {
// encapsulation key, drawing random bytes from a DRBG.
//
// The shared key must be kept secret.
func (ek *EncapsulationKey1024) Encapsulate() (ciphertext, sharedKey []byte) {
func (ek *EncapsulationKey1024) Encapsulate() (sharedKey, ciphertext []byte) {
// The actual logic is in a separate function to outline this allocation.
var cc [CiphertextSize1024]byte
return ek.encapsulate(&cc)
}
func (ek *EncapsulationKey1024) encapsulate(cc *[CiphertextSize1024]byte) (ciphertext, sharedKey []byte) {
func (ek *EncapsulationKey1024) encapsulate(cc *[CiphertextSize1024]byte) (sharedKey, ciphertext []byte) {
var m [messageSize]byte
drbg.Read(m[:])
// Note that the modulus check (step 2 of the encapsulation key check from
@ -221,7 +221,7 @@ func (ek *EncapsulationKey1024) encapsulate(cc *[CiphertextSize1024]byte) (ciphe
// EncapsulateInternal is a derandomized version of Encapsulate, exclusively for
// use in tests.
func (ek *EncapsulationKey1024) EncapsulateInternal(m *[32]byte) (ciphertext, sharedKey []byte) {
func (ek *EncapsulationKey1024) EncapsulateInternal(m *[32]byte) (sharedKey, ciphertext []byte) {
cc := &[CiphertextSize1024]byte{}
return kemEncaps1024(cc, ek, m)
}
@ -229,14 +229,14 @@ func (ek *EncapsulationKey1024) EncapsulateInternal(m *[32]byte) (ciphertext, sh
// kemEncaps1024 generates a shared key and an associated ciphertext.
//
// It implements ML-KEM.Encaps_internal according to FIPS 203, Algorithm 17.
func kemEncaps1024(cc *[CiphertextSize1024]byte, ek *EncapsulationKey1024, m *[messageSize]byte) (c, K []byte) {
func kemEncaps1024(cc *[CiphertextSize1024]byte, ek *EncapsulationKey1024, m *[messageSize]byte) (K, c []byte) {
g := sha3.New512()
g.Write(m[:])
g.Write(ek.h[:])
G := g.Sum(nil)
K, r := G[:SharedKeySize], G[SharedKeySize:]
c = pkeEncrypt1024(cc, &ek.encryptionKey1024, m, r)
return c, K
return K, c
}
// NewEncapsulationKey1024 parses an encapsulation key from its encoded form.

12
src/crypto/internal/fips140/mlkem/mlkem768.go
View file

@ -246,7 +246,7 @@ func kemKeyGen(dk *DecapsulationKey768, d, z *[32]byte) {
// the first operational use (if not exported before the first use)."
func kemPCT(dk *DecapsulationKey768) error {
ek := dk.EncapsulationKey()
c, K := ek.Encapsulate()
K, c := ek.Encapsulate()
K1, err := dk.Decapsulate(c)
if err != nil {
return err
@ -261,13 +261,13 @@ func kemPCT(dk *DecapsulationKey768) error {
// encapsulation key, drawing random bytes from a DRBG.
//
// The shared key must be kept secret.
func (ek *EncapsulationKey768) Encapsulate() (ciphertext, sharedKey []byte) {
func (ek *EncapsulationKey768) Encapsulate() (sharedKey, ciphertext []byte) {
// The actual logic is in a separate function to outline this allocation.
var cc [CiphertextSize768]byte
return ek.encapsulate(&cc)
}
func (ek *EncapsulationKey768) encapsulate(cc *[CiphertextSize768]byte) (ciphertext, sharedKey []byte) {
func (ek *EncapsulationKey768) encapsulate(cc *[CiphertextSize768]byte) (sharedKey, ciphertext []byte) {
var m [messageSize]byte
drbg.Read(m[:])
// Note that the modulus check (step 2 of the encapsulation key check from
@ -278,7 +278,7 @@ func (ek *EncapsulationKey768) encapsulate(cc *[CiphertextSize768]byte) (ciphert
// EncapsulateInternal is a derandomized version of Encapsulate, exclusively for
// use in tests.
func (ek *EncapsulationKey768) EncapsulateInternal(m *[32]byte) (ciphertext, sharedKey []byte) {
func (ek *EncapsulationKey768) EncapsulateInternal(m *[32]byte) (sharedKey, ciphertext []byte) {
cc := &[CiphertextSize768]byte{}
return kemEncaps(cc, ek, m)
}
@ -286,14 +286,14 @@ func (ek *EncapsulationKey768) EncapsulateInternal(m *[32]byte) (ciphertext, sha
// kemEncaps generates a shared key and an associated ciphertext.
//
// It implements ML-KEM.Encaps_internal according to FIPS 203, Algorithm 17.
func kemEncaps(cc *[CiphertextSize768]byte, ek *EncapsulationKey768, m *[messageSize]byte) (c, K []byte) {
func kemEncaps(cc *[CiphertextSize768]byte, ek *EncapsulationKey768, m *[messageSize]byte) (K, c []byte) {
g := sha3.New512()
g.Write(m[:])
g.Write(ek.h[:])
G := g.Sum(nil)
K, r := G[:SharedKeySize], G[SharedKeySize:]
c = pkeEncrypt(cc, &ek.encryptionKey, m, r)
return c, K
return K, c
}
// NewEncapsulationKey768 parses an encapsulation key from its encoded form.

2
src/crypto/mlkem/mlkem1024.go
View file

@ -91,6 +91,6 @@ func (ek *EncapsulationKey1024) Bytes() []byte {
// encapsulation key, drawing random bytes from crypto/rand.
//
// The shared key must be kept secret.
func (ek *EncapsulationKey1024) Encapsulate() (ciphertext, sharedKey []byte) {
func (ek *EncapsulationKey1024) Encapsulate() (sharedKey, ciphertext []byte) {
return ek.key.Encapsulate()
}

2
src/crypto/mlkem/mlkem768.go
View file

@ -101,6 +101,6 @@ func (ek *EncapsulationKey768) Bytes() []byte {
// encapsulation key, drawing random bytes from crypto/rand.
//
// The shared key must be kept secret.
func (ek *EncapsulationKey768) Encapsulate() (ciphertext, sharedKey []byte) {
func (ek *EncapsulationKey768) Encapsulate() (sharedKey, ciphertext []byte) {
return ek.key.Encapsulate()
}

18
src/crypto/mlkem/mlkem_test.go
View file

@ -43,7 +43,7 @@ func testRoundTrip[E encapsulationKey, D decapsulationKey[E]](
t.Fatal(err)
}
ek := dk.EncapsulationKey()
c, Ke := ek.Encapsulate()
Ke, c := ek.Encapsulate()
Kd, err := dk.Decapsulate(c)
if err != nil {
t.Fatal(err)
@ -66,7 +66,7 @@ func testRoundTrip[E encapsulationKey, D decapsulationKey[E]](
if !bytes.Equal(dk.Bytes(), dk1.Bytes()) {
t.Fail()
}
c1, Ke1 := ek1.Encapsulate()
Ke1, c1 := ek1.Encapsulate()
Kd1, err := dk1.Decapsulate(c1)
if err != nil {
t.Fatal(err)
@ -86,7 +86,7 @@ func testRoundTrip[E encapsulationKey, D decapsulationKey[E]](
t.Fail()
}
c2, Ke2 := dk.EncapsulationKey().Encapsulate()
Ke2, c2 := dk.EncapsulationKey().Encapsulate()
if bytes.Equal(c, c2) {
t.Fail()
}
@ -115,7 +115,7 @@ func testBadLengths[E encapsulationKey, D decapsulationKey[E]](
}
ek := dk.EncapsulationKey()
ekBytes := dk.EncapsulationKey().Bytes()
c, _ := ek.Encapsulate()
_, c := ek.Encapsulate()
for i := 0; i < len(dkBytes)-1; i++ {
if _, err := newDecapsulationKey(dkBytes[:i]); err == nil {
@ -189,7 +189,7 @@ func TestAccumulated(t *testing.T) {
o.Write(ek.Bytes())
s.Read(msg[:])
ct, k := ek.key.EncapsulateInternal(&msg)
k, ct := ek.key.EncapsulateInternal(&msg)
o.Write(ct)
o.Write(k)
@ -244,7 +244,7 @@ func BenchmarkEncaps(b *testing.B) {
if err != nil {
b.Fatal(err)
}
c, K := ek.key.EncapsulateInternal(&m)
K, c := ek.key.EncapsulateInternal(&m)
sink ^= c[0] ^ K[0]
}
}
@ -255,7 +255,7 @@ func BenchmarkDecaps(b *testing.B) {
b.Fatal(err)
}
ek := dk.EncapsulationKey()
c, _ := ek.Encapsulate()
_, c := ek.Encapsulate()
b.ResetTimer()
for i := 0; i < b.N; i++ {
K, _ := dk.Decapsulate(c)
@ -270,7 +270,7 @@ func BenchmarkRoundTrip(b *testing.B) {
}
ek := dk.EncapsulationKey()
ekBytes := ek.Bytes()
c, _ := ek.Encapsulate()
_, c := ek.Encapsulate()
if err != nil {
b.Fatal(err)
}
@ -296,7 +296,7 @@ func BenchmarkRoundTrip(b *testing.B) {
if err != nil {
b.Fatal(err)
}
cS, Ks := ek.Encapsulate()
Ks, cS := ek.Encapsulate()
if err != nil {
b.Fatal(err)
}

2
src/crypto/tls/handshake_server_tls13.go
View file

@ -280,7 +280,7 @@ func (hs *serverHandshakeStateTLS13) processClientHello() error {
c.sendAlert(alertIllegalParameter)
return errors.New("tls: invalid X25519MLKEM768 client key share")
}
ciphertext, mlkemSharedSecret := k.Encapsulate()
mlkemSharedSecret, ciphertext := k.Encapsulate()
// draft-kwiatkowski-tls-ecdhe-mlkem-02, Section 3.1.3: "For
// X25519MLKEM768, the shared secret is the concatenation of the ML-KEM
// shared secret and the X25519 shared secret. The shared secret is 64