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Add mkem scheme for pigeonhole mixnet protocols
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,128 @@ | ||
| // SPDX-FileCopyrightText: Copyright (C) 2024 David Stainton | ||
| // SPDX-License-Identifier: AGPL-3.0-only | ||
|
|
||
| // Package mkem provides multiparty KEM construction. | ||
| package mkem | ||
|
|
||
| import ( | ||
| "crypto/cipher" | ||
| "crypto/rand" | ||
| "errors" | ||
|
|
||
| "github.com/katzenpost/chacha20poly1305" | ||
| "github.com/katzenpost/hpqc/hash" | ||
| "github.com/katzenpost/hpqc/nike" | ||
| ) | ||
|
|
||
| type MKEMCiphertext struct { | ||
| EphemeralPublicKey *PublicKey | ||
| DEKCiphertexts [][]byte | ||
| SecretCiphertext []byte | ||
| } | ||
|
|
||
| // Scheme is an MKEM scheme. | ||
| type Scheme struct { | ||
| nike nike.Scheme | ||
| } | ||
|
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| // FromNIKE creates a new KEM adapter Scheme | ||
| // using the given NIKE Scheme. | ||
| func FromNIKE(nike nike.Scheme) *Scheme { | ||
| if nike == nil { | ||
| panic("NIKE is nil") | ||
| } | ||
| return &Scheme{ | ||
| nike: nike, | ||
| } | ||
| } | ||
|
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| func (s *Scheme) GenerateKeyPair() (*PublicKey, *PrivateKey, error) { | ||
| pubkey, privkey, err := s.nike.GenerateKeyPair() | ||
| if err != nil { | ||
| return nil, nil, err | ||
| } | ||
| return &PublicKey{ | ||
| publicKey: pubkey, | ||
| }, &PrivateKey{ | ||
| privateKey: privkey, | ||
| }, nil | ||
| } | ||
|
|
||
| func (s *Scheme) createCipher(key []byte) cipher.AEAD { | ||
| aead, err := chacha20poly1305.New(key) | ||
| if err != nil { | ||
| panic(err) | ||
| } | ||
| return aead | ||
| } | ||
|
|
||
| func (s *Scheme) encrypt(key []byte, plaintext []byte) []byte { | ||
| aead := s.createCipher(key) | ||
| nonce := make([]byte, aead.NonceSize()) | ||
| _, err := rand.Reader.Read(nonce) | ||
| if err != nil { | ||
| panic(err) | ||
| } | ||
| return aead.Seal(nonce, nonce, plaintext, nil) | ||
| } | ||
|
|
||
| func (s *Scheme) decrypt(key []byte, ciphertext []byte) ([]byte, error) { | ||
| aead := s.createCipher(key) | ||
| nonce := ciphertext[:aead.NonceSize()] | ||
| ciphertext = ciphertext[aead.NonceSize():] | ||
| return aead.Open(nil, nonce, ciphertext, nil) | ||
| } | ||
|
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| func (s *Scheme) Encapsulate(keys []*PublicKey, sharedSecret []byte) *MKEMCiphertext { | ||
| ephPub, ephPriv, err := s.nike.GenerateKeyPair() | ||
| if err != nil { | ||
| panic(err) | ||
| } | ||
|
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||
| secrets := make([][hash.HashSize]byte, len(keys)) | ||
| for i := 0; i < len(keys); i++ { | ||
| secrets[i] = hash.Sum256(s.nike.DeriveSecret(ephPriv, keys[i].publicKey)) | ||
| } | ||
|
|
||
| msgKey := make([]byte, 32) | ||
| _, err = rand.Reader.Read(msgKey) | ||
| if err != nil { | ||
| panic(err) | ||
| } | ||
| secretCiphertext := s.encrypt(msgKey, sharedSecret) | ||
|
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| outCiphertexts := make([][]byte, len(secrets)) | ||
| for i := 0; i < len(secrets); i++ { | ||
| outCiphertexts[i] = s.encrypt(secrets[i][:], msgKey) | ||
| } | ||
|
|
||
| return &MKEMCiphertext{ | ||
| EphemeralPublicKey: &PublicKey{ | ||
| publicKey: ephPub, | ||
| }, | ||
| DEKCiphertexts: outCiphertexts, | ||
| SecretCiphertext: secretCiphertext, | ||
| } | ||
| } | ||
|
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| func (s *Scheme) Decapsulate(privkey *PrivateKey, c *MKEMCiphertext) ([]byte, error) { | ||
| ephSecret := hash.Sum256(s.nike.DeriveSecret(privkey.privateKey, c.EphemeralPublicKey.publicKey)) | ||
| for i := 0; i < len(c.DEKCiphertexts); i++ { | ||
| msgKey, err := s.decrypt(ephSecret[:], c.DEKCiphertexts[i]) | ||
| if err != nil { | ||
| continue | ||
| } | ||
| return s.decrypt(msgKey, c.SecretCiphertext) | ||
| } | ||
| return nil, errors.New("failed to trial decrypt") | ||
| } | ||
|
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| // PrivateKey is an MKEM private key. | ||
| type PrivateKey struct { | ||
| privateKey nike.PrivateKey | ||
| } | ||
|
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||
| // PublicKey is an MKEM public key. | ||
| type PublicKey struct { | ||
| publicKey nike.PublicKey | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,41 @@ | ||
| // SPDX-FileCopyrightText: Copyright (C) 2024 David Stainton | ||
| // SPDX-License-Identifier: AGPL-3.0-only | ||
|
|
||
| // Package mkem provides multiparty KEM construction. | ||
| package mkem | ||
|
|
||
| import ( | ||
| "crypto/rand" | ||
| "testing" | ||
|
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| "github.com/katzenpost/hpqc/nike/schemes" | ||
| "github.com/stretchr/testify/require" | ||
| ) | ||
|
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| func TestMKEMCorrectness(t *testing.T) { | ||
| nikeName := "x25519" | ||
| nike := schemes.ByName(nikeName) | ||
| s := FromNIKE(nike) | ||
|
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| replica1pub, replica1priv, err := s.GenerateKeyPair() | ||
| require.NoError(t, err) | ||
|
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| replica2pub, replica2priv, err := s.GenerateKeyPair() | ||
| require.NoError(t, err) | ||
|
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| secret := make([]byte, 32) | ||
| _, err = rand.Reader.Read(secret) | ||
| require.NoError(t, err) | ||
|
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| ciphertext := s.Encapsulate([]*PublicKey{replica1pub, replica2pub}, secret) | ||
|
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| secret1, err := s.Decapsulate(replica1priv, ciphertext) | ||
| require.NoError(t, err) | ||
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| require.Equal(t, secret, secret1) | ||
|
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| secret2, err := s.Decapsulate(replica2priv, ciphertext) | ||
| require.NoError(t, err) | ||
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| require.Equal(t, secret, secret2) | ||
| } |