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| 1 | +package xwing |
| 2 | + |
| 3 | +import ( |
| 4 | + "bytes" |
| 5 | + cryptoRand "crypto/rand" |
| 6 | + "crypto/subtle" |
| 7 | + |
| 8 | + "github.com/cloudflare/circl/kem" |
| 9 | + "github.com/cloudflare/circl/kem/mlkem/mlkem768" |
| 10 | +) |
| 11 | + |
| 12 | +// This file contains the boilerplate code to connect X-Wing to the |
| 13 | +// generic KEM API. |
| 14 | + |
| 15 | +// Returns the generic KEM interface for X-Wing PQ/T hybrid KEM. |
| 16 | +func Scheme() kem.Scheme { return &xwing } |
| 17 | + |
| 18 | +type scheme struct{} |
| 19 | + |
| 20 | +var xwing scheme |
| 21 | + |
| 22 | +func (*scheme) Name() string { return "X-Wing" } |
| 23 | +func (*scheme) PublicKeySize() int { return PublicKeySize } |
| 24 | +func (*scheme) PrivateKeySize() int { return PrivateKeySize } |
| 25 | +func (*scheme) SeedSize() int { return SeedSize } |
| 26 | +func (*scheme) EncapsulationSeedSize() int { return EncapsulationSeedSize } |
| 27 | +func (*scheme) SharedKeySize() int { return SharedKeySize } |
| 28 | +func (*scheme) CiphertextSize() int { return CiphertextSize } |
| 29 | +func (*PrivateKey) Scheme() kem.Scheme { return &xwing } |
| 30 | +func (*PublicKey) Scheme() kem.Scheme { return &xwing } |
| 31 | + |
| 32 | +func (sch *scheme) Encapsulate(pk kem.PublicKey) (ct, ss []byte, err error) { |
| 33 | + var seed [EncapsulationSeedSize]byte |
| 34 | + _, err = cryptoRand.Read(seed[:]) |
| 35 | + if err != nil { |
| 36 | + return |
| 37 | + } |
| 38 | + return sch.EncapsulateDeterministically(pk, seed[:]) |
| 39 | +} |
| 40 | + |
| 41 | +func (sch *scheme) EncapsulateDeterministically( |
| 42 | + pk kem.PublicKey, seed []byte, |
| 43 | +) ([]byte, []byte, error) { |
| 44 | + if len(seed) != EncapsulationSeedSize { |
| 45 | + return nil, nil, kem.ErrSeedSize |
| 46 | + } |
| 47 | + pub, ok := pk.(*PublicKey) |
| 48 | + if !ok { |
| 49 | + return nil, nil, kem.ErrTypeMismatch |
| 50 | + } |
| 51 | + var ( |
| 52 | + ct [CiphertextSize]byte |
| 53 | + ss [SharedKeySize]byte |
| 54 | + ) |
| 55 | + pub.EncapsulateTo(ct[:], ss[:], seed) |
| 56 | + return ct[:], ss[:], nil |
| 57 | +} |
| 58 | + |
| 59 | +func (*scheme) UnmarshalBinaryPublicKey(buf []byte) (kem.PublicKey, error) { |
| 60 | + var pk PublicKey |
| 61 | + if len(buf) != PublicKeySize { |
| 62 | + return nil, kem.ErrPubKeySize |
| 63 | + } |
| 64 | + |
| 65 | + if err := pk.Unpack(buf); err != nil { |
| 66 | + return nil, err |
| 67 | + } |
| 68 | + return &pk, nil |
| 69 | +} |
| 70 | + |
| 71 | +func (*scheme) UnmarshalBinaryPrivateKey(buf []byte) (kem.PrivateKey, error) { |
| 72 | + var sk PrivateKey |
| 73 | + if len(buf) != PrivateKeySize { |
| 74 | + return nil, kem.ErrPrivKeySize |
| 75 | + } |
| 76 | + |
| 77 | + sk.Unpack(buf) |
| 78 | + return &sk, nil |
| 79 | +} |
| 80 | + |
| 81 | +func (sk *PrivateKey) MarshalBinary() ([]byte, error) { |
| 82 | + var ret [PrivateKeySize]byte |
| 83 | + sk.Pack(ret[:]) |
| 84 | + return ret[:], nil |
| 85 | +} |
| 86 | + |
| 87 | +func (sk *PrivateKey) Equal(other kem.PrivateKey) bool { |
| 88 | + oth, ok := other.(*PrivateKey) |
| 89 | + if !ok { |
| 90 | + return false |
| 91 | + } |
| 92 | + return sk.m.Equal(&oth.m) && |
| 93 | + subtle.ConstantTimeCompare(oth.x[:], sk.x[:]) == 1 |
| 94 | +} |
| 95 | + |
| 96 | +func (sk *PrivateKey) Public() kem.PublicKey { |
| 97 | + var pk PublicKey |
| 98 | + pk.m = *(sk.m.Public().(*mlkem768.PublicKey)) |
| 99 | + pk.x = sk.xpk |
| 100 | + return &pk |
| 101 | +} |
| 102 | + |
| 103 | +func (pk *PublicKey) Equal(other kem.PublicKey) bool { |
| 104 | + oth, ok := other.(*PublicKey) |
| 105 | + if !ok { |
| 106 | + return false |
| 107 | + } |
| 108 | + return pk.m.Equal(&oth.m) && bytes.Equal(pk.x[:], oth.x[:]) |
| 109 | +} |
| 110 | + |
| 111 | +func (pk *PublicKey) MarshalBinary() ([]byte, error) { |
| 112 | + var ret [PublicKeySize]byte |
| 113 | + pk.Pack(ret[:]) |
| 114 | + return ret[:], nil |
| 115 | +} |
| 116 | + |
| 117 | +func (*scheme) DeriveKeyPair(seed []byte) (kem.PublicKey, kem.PrivateKey) { |
| 118 | + sk, pk := DeriveKeyPair(seed) |
| 119 | + return pk, sk |
| 120 | +} |
| 121 | + |
| 122 | +func (sch *scheme) GenerateKeyPair() (kem.PublicKey, kem.PrivateKey, error) { |
| 123 | + sk, pk, err := GenerateKeyPair(nil) |
| 124 | + return pk, sk, err |
| 125 | +} |
| 126 | + |
| 127 | +func (*scheme) Decapsulate(sk kem.PrivateKey, ct []byte) ([]byte, error) { |
| 128 | + if len(ct) != CiphertextSize { |
| 129 | + return nil, kem.ErrCiphertextSize |
| 130 | + } |
| 131 | + |
| 132 | + var ss [SharedKeySize]byte |
| 133 | + |
| 134 | + priv, ok := sk.(*PrivateKey) |
| 135 | + if !ok { |
| 136 | + return nil, kem.ErrTypeMismatch |
| 137 | + } |
| 138 | + |
| 139 | + priv.DecapsulateTo(ss[:], ct[:]) |
| 140 | + |
| 141 | + return ss[:], nil |
| 142 | +} |
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