'''This file implements key generation for GSW encryption.'''

from util import *

from math import ceil, log2

import numpy as np

import random

class GSWKeys:

def __init__(self, k, q, t, e, A, B, datatype):

self.n = k

self.q = q

self.l = ceil(log2(q))

self.m = self.n * self.l

self.SK = t

self.e = e

self.A = A

self.PK = B

self.datatype = datatype

def keygen(k):

if k > 29:

datatype = 'object'

else:

datatype = np.int64

# pick a random Sophie Germain prime [q] in the range 2...2**k

# and get its bit length [l]

stat("Generating modulus")

q = generateSophieGermainPrime(k)

l = ceil(log2(q))

print(" "*12 + "q = %d" % q)

#

# the gadget matrix [G] is an n×m matrix (n rows, m = n×l columns)

#

# the secret vector [s] is an (n-1)-dimensional vector,

# the secret key [t] is -s‖1, an n-dimensional vector

#

# the error vector [e] is an m-dimensional vector

#

# the matrix [A] is an (n-1)×m matrix (n-1 rows, m = n×l columns)

#

# the public key [B] is ( A )

# ( sA+e )

#

stat("Generating secret key")

n = k

m = n*l

s = np.random.randint(q, size=n-1, dtype=np.int64).astype(datatype)

t = np.append(s, 1)

stat("Generating error vector")

e = np.rint(np.random.normal(scale=1.0, size=m)).astype(np.int).astype(datatype) # This makes me die a little bit on the inside.

stat("Generating random matrix")

A = np.random.randint(q, size=(n-1, m), dtype=np.int64).astype(datatype)

stat("Generating public key")

B = np.vstack((-A, np.dot(s, A) + e)) % q

check = np.dot(t, B) % q

okay = np.all(check == (e % q))

if okay:

stat("Keygen check passed") # t⋅B == e

else:

stat("\x1B[31;1mKeygen check failed\x1B[0m") # t⋅B != e

return GSWKeys(k, q, t, e, A, B, datatype)

if __name__ == '__main__':

keygen(48)