mamonraab / pybv

A Python Implementation of the BV Homomorphic Encryption Scheme

PyBV

A Python Implementation of the BV Homomorphic Encryption Scheme

The scheme was proposed by Lauter et al. in Can Homomorphic Encryption be Practical? which was a variant of a homomorphic encryption scheme given by Brakerski et al. in Fully Homomorphic Encryption from Ring-LWE and Security for Key Dependent Messages.

The API can be imported using the command "import BV". It currently supports the following functions and classes:

Running

1. Install Docker

   • If you're on macOS and use Homebrew, run brew cask install docker; open -a docker

2. Run these commands:

make build
make run

Development

1. Install Docker

   • If you're on macOS and use Homebrew, run brew cask install docker; open -a docker

2. Run make build

3. Edit source code as you wish

4. Run make dev

API

Functions:

pari_init(pari_size, max_prime)

pari_init() is the function that needs to be called before dealing with this API. On importing the module, the module executes this statement automatically. pari_size defines the size of stack we'll be using, and max_prime defines the pre-computed prime table. By default, pari_size is set to 2000000000, and max_prime is set to 2.

Arguments: pari_size (int), max_prime (int)

pari_close()

pari_close() function has to be called at the end of each program to clear the memory used.

Classes:

pari_GEN

This class abstracts the GEN variable in C++, making it available through a Python interface. The class is compatible with +, *, /, -, __getitem__ , %, and print.

• Class Data:

  1. value (GEN)

• __init__(self, x)

  The constructor converts x to a GEN variable.

  Arguments: x(int)

parameters

• Class Data:
  1. n, Q, sigma (ints)
  2. q, t, F (pari_GEN)

secret_key

• Class Data:

  1. sk (pari_GEN)
  2. params (parameters)

• __init__(self, sk = None, parmas = None) The constructor initiates class data.

  Arguments: sk (pari_GEN), params (parameters)

• decrypt(self, ct)
decrypt() method returns the plaintext (pari_GEN) encrypted in ciphertext ct.

  Arguments: ct (pari_GEN)

• serialize(self)
  TO BE IMPLEMENTED

public_key

• Class Data:

  1. pk (pari_GEN)
  2. params (parameters*)

• __init__(self, pk = None, params = None)
  The constructor initiates the class data.

  Arguments: pk (pari_GEN), params (parameters*)

• encrypt(self, pt)
encrypt() method returns the ciphertext (pari_GEN) which encrypts plaintext pt.

  Arguments: pt (pari_GEN)

• serialize(self)
  TO BE IMPLEMENTED

key_pair

• Class Data:
  1. sk (secret_key)
  2. pk (public_key)

key_gen

• generate_key(self, n, Q, T, sigma)

  generate_key() method returns the keys, which is of type key_pair.

  Arguments: n (int), Q (int), T (int), sigma (int)

• deserialize(self)
  TO BE IMPLEMENTED

ciphertext

The class is compatible with '+', '*', and '-' operators. It also supports multiplication with plaintext (int) and batching.

• Class Data:

  1. value (pari_GEN)
  2. pk (public_key*)

• __init__(self, plaintext = None, pk)

  The plaintext variable is either an int variable, or it is an int_list variable. The size of list has to be less than the degree of polynomials (paramter n) in the polynomial ring.

  Arguments: plaintext (int or int_list), pk (public_key*)

• decrypt(self, sk)

  decrypt() method returns the decrypted ciphertext which is pari_GEN variable.

  Arguments: sk (secret_key*)

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