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Add hybrid post-quantum key agreement.
Adds X25519Kyber512Draft00 and X25519Kyber768Draft00 hybrid post-quantum key
agreements with temporary group identifiers.
The hybrid post-quantum key exchanges uses plain X{25519,448} instead
of HPKE, which we assume will be more likely to be adopted. The order
is chosen to match CECPQ2.
Not enabled by default.
Adds CFEvents to detect `HelloRetryRequest`s and to signal which
key agreement was used.
Cf #121 #122 #123 #132
Co-authored-by: Christopher Wood <[email protected]>- Loading branch information
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,208 @@ | ||
| package hybrid | ||
|
|
||
| import ( | ||
| "bytes" | ||
| cryptoRand "crypto/rand" | ||
| "crypto/subtle" | ||
|
|
||
| "circl/dh/x25519" | ||
| "circl/dh/x448" | ||
| "circl/internal/sha3" | ||
| "circl/kem" | ||
| ) | ||
|
|
||
| type xPublicKey struct { | ||
| scheme *xScheme | ||
| key []byte | ||
| } | ||
| type xPrivateKey struct { | ||
| scheme *xScheme | ||
| key []byte | ||
| } | ||
| type xScheme struct { | ||
| size int | ||
| } | ||
|
|
||
| var ( | ||
| x25519Kem = &xScheme{x25519.Size} | ||
| x448Kem = &xScheme{x448.Size} | ||
| ) | ||
|
|
||
| func (sch *xScheme) Name() string { | ||
| switch sch.size { | ||
| case x25519.Size: | ||
| return "X25519" | ||
| case x448.Size: | ||
| return "X448" | ||
| } | ||
| panic(kem.ErrTypeMismatch) | ||
| } | ||
|
|
||
| func (sch *xScheme) PublicKeySize() int { return sch.size } | ||
| func (sch *xScheme) PrivateKeySize() int { return sch.size } | ||
| func (sch *xScheme) SeedSize() int { return sch.size } | ||
| func (sch *xScheme) SharedKeySize() int { return sch.size } | ||
| func (sch *xScheme) CiphertextSize() int { return sch.size } | ||
| func (sch *xScheme) EncapsulationSeedSize() int { return sch.size } | ||
|
|
||
| func (sk *xPrivateKey) Scheme() kem.Scheme { return sk.scheme } | ||
| func (pk *xPublicKey) Scheme() kem.Scheme { return pk.scheme } | ||
|
|
||
| func (sk *xPrivateKey) MarshalBinary() ([]byte, error) { | ||
| ret := make([]byte, len(sk.key)) | ||
| copy(ret, sk.key) | ||
| return ret, nil | ||
| } | ||
|
|
||
| func (sk *xPrivateKey) Equal(other kem.PrivateKey) bool { | ||
| oth, ok := other.(*xPrivateKey) | ||
| if !ok { | ||
| return false | ||
| } | ||
| if oth.scheme != sk.scheme { | ||
| return false | ||
| } | ||
| return subtle.ConstantTimeCompare(oth.key, sk.key) == 1 | ||
| } | ||
|
|
||
| func (sk *xPrivateKey) Public() kem.PublicKey { | ||
| pk := xPublicKey{sk.scheme, make([]byte, sk.scheme.size)} | ||
| switch sk.scheme.size { | ||
| case x25519.Size: | ||
| var sk2, pk2 x25519.Key | ||
| copy(sk2[:], sk.key) | ||
| x25519.KeyGen(&pk2, &sk2) | ||
| copy(pk.key, pk2[:]) | ||
| case x448.Size: | ||
| var sk2, pk2 x448.Key | ||
| copy(sk2[:], sk.key) | ||
| x448.KeyGen(&pk2, &sk2) | ||
| copy(pk.key, pk2[:]) | ||
| } | ||
| return &pk | ||
| } | ||
|
|
||
| func (pk *xPublicKey) Equal(other kem.PublicKey) bool { | ||
| oth, ok := other.(*xPublicKey) | ||
| if !ok { | ||
| return false | ||
| } | ||
| if oth.scheme != pk.scheme { | ||
| return false | ||
| } | ||
| return bytes.Equal(oth.key, pk.key) | ||
| } | ||
|
|
||
| func (pk *xPublicKey) MarshalBinary() ([]byte, error) { | ||
| ret := make([]byte, pk.scheme.size) | ||
| copy(ret, pk.key) | ||
| return ret, nil | ||
| } | ||
|
|
||
| func (sch *xScheme) GenerateKeyPair() (kem.PublicKey, kem.PrivateKey, error) { | ||
| seed := make([]byte, sch.SeedSize()) | ||
| _, err := cryptoRand.Read(seed) | ||
| if err != nil { | ||
| return nil, nil, err | ||
| } | ||
| pk, sk := sch.DeriveKeyPair(seed) | ||
| return pk, sk, nil | ||
| } | ||
|
|
||
| func (sch *xScheme) DeriveKeyPair(seed []byte) (kem.PublicKey, kem.PrivateKey) { | ||
| if len(seed) != sch.SeedSize() { | ||
| panic(kem.ErrSeedSize) | ||
| } | ||
| sk := xPrivateKey{scheme: sch, key: make([]byte, sch.size)} | ||
|
|
||
| h := sha3.NewShake256() | ||
| _, _ = h.Write(seed) | ||
| _, _ = h.Read(sk.key) | ||
|
|
||
| return sk.Public(), &sk | ||
| } | ||
|
|
||
| func (sch *xScheme) Encapsulate(pk kem.PublicKey) (ct, ss []byte, err error) { | ||
| seed := make([]byte, sch.EncapsulationSeedSize()) | ||
| _, err = cryptoRand.Read(seed) | ||
| if err != nil { | ||
| return | ||
| } | ||
| return sch.EncapsulateDeterministically(pk, seed) | ||
| } | ||
|
|
||
| func (pk *xPublicKey) X(sk *xPrivateKey) []byte { | ||
| if pk.scheme != sk.scheme { | ||
| panic(kem.ErrTypeMismatch) | ||
| } | ||
|
|
||
| switch pk.scheme.size { | ||
| case x25519.Size: | ||
| var ss2, pk2, sk2 x25519.Key | ||
| copy(pk2[:], pk.key) | ||
| copy(sk2[:], sk.key) | ||
| x25519.Shared(&ss2, &sk2, &pk2) | ||
| return ss2[:] | ||
| case x448.Size: | ||
| var ss2, pk2, sk2 x448.Key | ||
| copy(pk2[:], pk.key) | ||
| copy(sk2[:], sk.key) | ||
| x448.Shared(&ss2, &sk2, &pk2) | ||
| return ss2[:] | ||
| } | ||
| panic(kem.ErrTypeMismatch) | ||
| } | ||
|
|
||
| func (sch *xScheme) EncapsulateDeterministically( | ||
| pk kem.PublicKey, seed []byte, | ||
| ) (ct, ss []byte, err error) { | ||
| if len(seed) != sch.EncapsulationSeedSize() { | ||
| return nil, nil, kem.ErrSeedSize | ||
| } | ||
| pub, ok := pk.(*xPublicKey) | ||
| if !ok || pub.scheme != sch { | ||
| return nil, nil, kem.ErrTypeMismatch | ||
| } | ||
|
|
||
| pk2, sk2 := sch.DeriveKeyPair(seed) | ||
| ss = pub.X(sk2.(*xPrivateKey)) | ||
| ct, _ = pk2.MarshalBinary() | ||
| return | ||
| } | ||
|
|
||
| func (sch *xScheme) Decapsulate(sk kem.PrivateKey, ct []byte) ([]byte, error) { | ||
| if len(ct) != sch.CiphertextSize() { | ||
| return nil, kem.ErrCiphertextSize | ||
| } | ||
|
|
||
| priv, ok := sk.(*xPrivateKey) | ||
| if !ok || priv.scheme != sch { | ||
| return nil, kem.ErrTypeMismatch | ||
| } | ||
|
|
||
| pk, err := sch.UnmarshalBinaryPublicKey(ct) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| ss := pk.(*xPublicKey).X(priv) | ||
| return ss, nil | ||
| } | ||
|
|
||
| func (sch *xScheme) UnmarshalBinaryPublicKey(buf []byte) (kem.PublicKey, error) { | ||
| if len(buf) != sch.PublicKeySize() { | ||
| return nil, kem.ErrPubKeySize | ||
| } | ||
| ret := xPublicKey{sch, make([]byte, sch.size)} | ||
| copy(ret.key, buf) | ||
| return &ret, nil | ||
| } | ||
|
|
||
| func (sch *xScheme) UnmarshalBinaryPrivateKey(buf []byte) (kem.PrivateKey, error) { | ||
| if len(buf) != sch.PrivateKeySize() { | ||
| return nil, kem.ErrPrivKeySize | ||
| } | ||
| ret := xPrivateKey{sch, make([]byte, sch.size)} | ||
| copy(ret.key, buf) | ||
| return &ret, nil | ||
| } |
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