CryptoSystem Interface

The CryptoSystem interface provides a uniform API for cryptographic operations such as key generation, encryption, decryption, and homomorphic arithmetic operations. It is designed to abstract different underlying cryptosystem implementations, allowing for CPU or GPU-based backends while maintaining the same interface for users.

Note: The current CPUCryptoSystem class uses pointers for underlying implementations in tensors and vectors. This will be updated in the future to strictly follow the interface described below.

Template Parameters

template <
    typename CryptoSystemImpl,
    typename SecretKeyImpl,
    typename PublicKeyImpl,
    typename PlainTextImpl,
    typename CipherTextImpl,
    typename SecretKeyShareImpl,
    typename PartDecryptionResult
>

CryptoSystemImpl: The implementation of the cryptosystem.
SecretKeyImpl: The type representing the secret key.
PublicKeyImpl: The type representing the public key.
PlainTextImpl: The type representing plaintext data.
CipherTextImpl: The type representing ciphertext data.
SecretKeyShareImpl: The type representing a share of the secret key (used in distributed settings).
PartDecryptionResult: The type representing the result of a partial decryption.

Interface Functions

Key Generation

SecretKeyImpl keygen()
Generates a new secret key.
```
SecretKeyImpl sk = cs.keygen();
```
PublicKeyImpl keygen(SecretKeyImpl sk)
Generates a public key from the given secret key.
```
PublicKeyImpl pk = cs.keygen(sk);
```
Vector<Vector<SecretKeyShareImpl>> keygen(SecretKeyImpl sk, int threshold, int num_parties)
Generates secret key shares for threshold decryption in a distributed setting.
```
auto sk_shares = cs.keygen(sk, threshold, num_parties);
```

Encryption

CipherTextImpl encrypt(PublicKeyImpl pk, PlainTextImpl pt)
Encrypts a plaintext using the public key.
```
CipherTextImpl ct = cs.encrypt(pk, pt);
```
Vector<CipherTextImpl> encrypt(PublicKeyImpl pk, Vector<PlainTextImpl> pts)
Encrypts a vector of plaintexts.
```
Vector<CipherTextImpl> cts = cs.encrypt(pk, pts);
```
Tensor<CipherTextImpl> encrypt_tensor(PublicKeyImpl pk, Tensor<PlainTextImpl> pts)
Encrypts a tensor of plaintexts.
```
Tensor<CipherTextImpl> cts = cs.encrypt_tensor(pk, pts);
```

Decryption

PlainTextImpl decrypt(SecretKeyImpl sk, CipherTextImpl ct)
Decrypts a ciphertext using the secret key.
```
PlainTextImpl pt = cs.decrypt(sk, ct);
```
Vector<PlainTextImpl> decrypt_vector(SecretKeyImpl sk, Vector<CipherTextImpl> cts)
Decrypts a vector of ciphertexts.
```
Vector<PlainTextImpl> pts = cs.decrypt_vector(sk, cts);
```
Tensor<PlainTextImpl> decrypt_tensor(SecretKeyImpl sk, Tensor<CipherTextImpl> cts)
Decrypts a tensor of ciphertexts.
```
Tensor<PlainTextImpl> pts = cs.decrypt_tensor(sk, cts);
```

Partial Decryption (Distributed)

PartDecryptionResult part_decrypt(SecretKeyShareImpl sks, CipherTextImpl ct)
Performs partial decryption using a secret key share.
```
PartDecryptionResult pdr = cs.part_decrypt(sks, ct);
```
Vector<PartDecryptionResult> part_decrypt_vector(SecretKeyShareImpl sks, Vector<CipherTextImpl> cts)
Partial decryption of a vector of ciphertexts.
```
Vector<PartDecryptionResult> pdrs = cs.part_decrypt_vector(sks, cts);
```
Tensor<PartDecryptionResult> part_decrypt_tensor(SecretKeyShareImpl sks, Tensor<CipherTextImpl> cts)
Partial decryption of a tensor of ciphertexts.
```
Tensor<PartDecryptionResult> pdrs = cs.part_decrypt_tensor(sks, cts);
```
PlainTextImpl combine_part_decryption_results(CipherTextImpl ct, Vector<PartDecryptionResult> pdrs)
Combines partial decryption results to recover the plaintext.
```
PlainTextImpl pt = cs.combine_part_decryption_results(ct, pdrs);
```
Vector<PlainTextImpl> combine_part_decryption_results_vector(CipherTextImpl ct, Vector<PartDecryptionResult> pdrs)
Combines partial decryption results for a vector of ciphertexts.
```
Vector<PlainTextImpl> pts = cs.combine_part_decryption_results_vector(ct, pdrs);
```
Tensor<PlainTextImpl> combine_part_decryption_results_tensor(CipherTextImpl ct, Vector<Tensor<PartDecryptionResult>> pdrs)
Combines partial decryption results for a tensor of ciphertexts.
```
Tensor<PlainTextImpl> pts = cs.combine_part_decryption_results_tensor(ct, pdrs);
```

Homomorphic Operations on Ciphertexts

CipherTextImpl add_ciphertexts(PublicKeyImpl pk, CipherTextImpl ct1, CipherTextImpl ct2)
Adds two ciphertexts homomorphically.
```
CipherTextImpl ct_sum = cs.add_ciphertexts(pk, ct1, ct2);
```
CipherTextImpl scal_ciphertext(PublicKeyImpl pk, PlainTextImpl pt, CipherTextImpl ct)
Multiplies a ciphertext by a plaintext scalar homomorphically.
```
CipherTextImpl ct_scaled = cs.scal_ciphertext(pk, pt, ct);
```
Vector<CipherTextImpl> add_ciphertext_vectors(PublicKeyImpl pk, Vector<CipherTextImpl> cts1, Vector<CipherTextImpl> cts2)
Adds two vectors of ciphertexts element-wise.
```
Vector<CipherTextImpl> cts_sum = cs.add_ciphertext_vectors(pk, cts1, cts2);
```
Vector<CipherTextImpl> scal_ciphertext_vector(PublicKeyImpl pk, PlainTextImpl pt, Vector<CipherTextImpl> cts)
Multiplies each ciphertext in the vector by a plaintext scalar.
```
Vector<CipherTextImpl> cts_scaled = cs.scal_ciphertext_vector(pk, pt, cts);
```
Vector<CipherTextImpl> scal_ciphertext_vector(PublicKeyImpl pk, Vector<PlainTextImpl> pts, Vector<CipherTextImpl> cts)
Multiplies each ciphertext in the vector by corresponding plaintext scalars.
```
Vector<CipherTextImpl> cts_scaled = cs.scal_ciphertext_vector(pk, pts, cts);
```
Tensor<CipherTextImpl> add_ciphertext_tensors(PublicKeyImpl pk, Tensor<CipherTextImpl> cts1, Tensor<CipherTextImpl> cts2)
Adds two tensors of ciphertexts element-wise.
```
Tensor<CipherTextImpl> cts_sum = cs.add_ciphertext_tensors(pk, cts1, cts2);
```
Tensor<CipherTextImpl> scal_ciphertext_tensors(PublicKeyImpl pk, Tensor<PlainTextImpl> pts, Tensor<CipherTextImpl> cts)
Multiplies each ciphertext in the tensor by corresponding plaintext scalars.
```
Tensor<CipherTextImpl> cts_scaled = cs.scal_ciphertext_tensors(pk, pts, cts);
```

Plaintext Operations

PlainTextImpl generate_random_plaintext()
Generates a random plaintext.
```
PlainTextImpl random_pt = cs.generate_random_plaintext();
```
Vector<PlainTextImpl> generate_random_beavers_triplet()
Generates a Beaver's triplet for secure multiplication.
```
Vector<PlainTextImpl> triplet = cs.generate_random_beavers_triplet();
```
PlainTextImpl add_plaintexts(PlainTextImpl pt1, PlainTextImpl pt2)
Adds two plaintexts.
```
PlainTextImpl pt_sum = cs.add_plaintexts(pt1, pt2);
```
PlainTextImpl multiply_plaintexts(PlainTextImpl pt1, PlainTextImpl pt2)
Multiplies two plaintexts.
```
PlainTextImpl pt_product = cs.multiply_plaintexts(pt1, pt2);
```
Tensor<PlainTextImpl> add_plaintext_tensors(Tensor<PlainTextImpl> pts1, Tensor<PlainTextImpl> pts2)
Adds two tensors of plaintexts element-wise.
```
Tensor<PlainTextImpl> pts_sum = cs.add_plaintext_tensors(pts1, pts2);
```
Tensor<PlainTextImpl> multiply_plaintext_tensors(Tensor<PlainTextImpl> pts1, Tensor<PlainTextImpl> pts2)
Multiplies two tensors of plaintexts element-wise.
```
Tensor<PlainTextImpl> pts_product = cs.multiply_plaintext_tensors(pts1, pts2);
```

Negation Operations

PlainTextImpl negate_plaintext(PlainTextImpl pt)
Negates a plaintext.
```
PlainTextImpl pt_neg = cs.negate_plaintext(pt);
```
Tensor<PlainTextImpl> negate_plain_tensor(Tensor<PlainTextImpl> pts)
Negates each plaintext in a tensor.
```
Tensor<PlainTextImpl> pts_neg = cs.negate_plain_tensor(pts);
```
CipherTextImpl negate_ciphertext(PublicKeyImpl pk, CipherTextImpl ct)
Negates a ciphertext homomorphically.
```
CipherTextImpl ct_neg = cs.negate_ciphertext(pk, ct);
```
Tensor<CipherTextImpl> negate_ciphertext_tensor(PublicKeyImpl pk, Tensor<CipherTextImpl> cts)
Negates each ciphertext in a tensor homomorphically.
```
Tensor<CipherTextImpl> cts_neg = cs.negate_ciphertext_tensor(pk, cts);
```

Plaintext Creation and Retrieval

PlainTextImpl make_plaintext(float value)
Creates a plaintext from a floating-point value.
```
PlainTextImpl pt = cs.make_plaintext(3.14f);
```
float get_float_from_plaintext(PlainTextImpl pt)
Retrieves the floating-point value from a plaintext.
```
float value = cs.get_float_from_plaintext(pt);
```

Serialization

String serialize()
Serializes the cryptosystem instance.
```
String serialized_cs = cs.serialize();
```
String serialize_secret_key(SecretKeyImpl sk)
Serializes a secret key.
```
String serialized_sk = cs.serialize_secret_key(sk);
```
String serialize_secret_key_share(SecretKeyShareImpl sks)
Serializes a secret key share.
```
String serialized_sks = cs.serialize_secret_key_share(sks);
```
String serialize_public_key(PublicKeyImpl pk)
Serializes a public key.
```
String serialized_pk = cs.serialize_public_key(pk);
```
String serialize_plaintext(PlainTextImpl pt)
Serializes a plaintext.
```
String serialized_pt = cs.serialize_plaintext(pt);
```
String serialize_ciphertext(CipherTextImpl ct)
Serializes a ciphertext.
```
String serialized_ct = cs.serialize_ciphertext(ct);
```
String serialize_part_decryption_result(PartDecryptionResult pdr)
Serializes a partial decryption result.
```
String serialized_pdr = cs.serialize_part_decryption_result(pdr);
```
String serialize_plaintext_tensor(Tensor<PlainTextImpl> pts)
Serializes a tensor of plaintexts.
```
String serialized_pts = cs.serialize_plaintext_tensor(pts);
```
String serialize_ciphertext_tensor(Tensor<CipherTextImpl> cts)
Serializes a tensor of ciphertexts.
```
String serialized_cts = cs.serialize_ciphertext_tensor(cts);
```
String serialize_part_decryption_result_tensor(Tensor<PartDecryptionResult> pdrs)
Serializes a tensor of partial decryption results.
```
String serialized_pdrs = cs.serialize_part_decryption_result_tensor(pdrs);
```

Deserialization

CryptoSystemImpl::deserialize(String data)
Deserializes a cryptosystem instance from a string.
```
CryptoSystemImpl cs = CryptoSystemImpl::deserialize(serialized_cs);
```
SecretKeyImpl deserialize_secret_key(String data)
Deserializes a secret key from a string.
```
SecretKeyImpl sk = cs.deserialize_secret_key(serialized_sk);
```
SecretKeyShareImpl deserialize_secret_key_share(String data)
Deserializes a secret key share from a string.
```
SecretKeyShareImpl sks = cs.deserialize_secret_key_share(serialized_sks);
```
PublicKeyImpl deserialize_public_key(String data)
Deserializes a public key from a string.
```
PublicKeyImpl pk = cs.deserialize_public_key(serialized_pk);
```
PlainTextImpl deserialize_plaintext(String data)
Deserializes a plaintext from a string.
```
PlainTextImpl pt = cs.deserialize_plaintext(serialized_pt);
```
CipherTextImpl deserialize_ciphertext(String data)
Deserializes a ciphertext from a string.
```
CipherTextImpl ct = cs.deserialize_ciphertext(serialized_ct);
```
PartDecryptionResult deserialize_part_decryption_result(String data)
Deserializes a partial decryption result from a string.
```
PartDecryptionResult pdr = cs.deserialize_part_decryption_result(serialized_pdr);
```
Tensor<PlainTextImpl> deserialize_plaintext_tensor(String data)
Deserializes a tensor of plaintexts from a string.
```
Tensor<PlainTextImpl> pts = cs.deserialize_plaintext_tensor(serialized_pts);
```
Tensor<CipherTextImpl> deserialize_ciphertext_tensor(String data)
Deserializes a tensor of ciphertexts from a string.
```
Tensor<CipherTextImpl> cts = cs.deserialize_ciphertext_tensor(serialized_cts);
```
Tensor<PartDecryptionResult> deserialize_part_decryption_result_tensor(String data)
Deserializes a tensor of partial decryption results from a string.
```
Tensor<PartDecryptionResult> pdrs = cs.deserialize_part_decryption_result_tensor(serialized_pdrs);
```

Notes

Serialization and deserialization facilitate the storage and transmission over network of cryptographic objects.

Example Usage

Key Generation and Encryption

// Generate keys
SecretKeyImpl sk = cs.keygen();
PublicKeyImpl pk = cs.keygen(sk);

// Create a plaintext
PlainTextImpl pt = cs.make_plaintext(42.0f);

// Encrypt the plaintext
CipherTextImpl ct = cs.encrypt(pk, pt);

Homomorphic Addition and Decryption

// Encrypt two plaintexts
PlainTextImpl pt1 = cs.make_plaintext(10.0f);
PlainTextImpl pt2 = cs.make_plaintext(15.0f);
CipherTextImpl ct1 = cs.encrypt(pk, pt1);
CipherTextImpl ct2 = cs.encrypt(pk, pt2);

// Perform homomorphic addition
CipherTextImpl ct_sum = cs.add_ciphertexts(pk, ct1, ct2);

// Decrypt the result
PlainTextImpl pt_sum = cs.decrypt(sk, ct_sum);
float result = cs.get_float_from_plaintext(pt_sum); // result should be 25.0f

Serialization and Deserialization

// Serialize keys and ciphertext
String serialized_sk = cs.serialize_secret_key(sk);
String serialized_pk = cs.serialize_public_key(pk);
String serialized_ct = cs.serialize_ciphertext(ct);

// Deserialize keys and ciphertext
SecretKeyImpl deserialized_sk = cs.deserialize_secret_key(serialized_sk);
PublicKeyImpl deserialized_pk = cs.deserialize_public_key(serialized_pk);
CipherTextImpl deserialized_ct = cs.deserialize_ciphertext(serialized_ct);

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