def TruncRoundNearest(a, k, m, kappa):
"""
Returns a / 2^m, rounded to the nearest integer.
k: bit length of m
m: compile-time integer
"""
from types import sint, cint
from library import reveal, load_int_to_secret
if m == 1:
lsb = sint()
Mod2(lsb, a, k, kappa, False)
return (a + lsb) / 2
r_dprime = sint()
r_prime = sint()
r = [sint() for i in range(m)]
u = sint()
PRandM(r_dprime, r_prime, r, k, m, kappa)
c = reveal((cint(1) << (k - 1)) + a + (cint(1) << m) * r_dprime + r_prime)
c_prime = c % (cint(1) << (m - 1))
if const_rounds:
BitLTC1(u, c_prime, r[:-1], kappa)
else:
BitLTL(u, c_prime, r[:-1], kappa)
bit = ((c - c_prime) / (cint(1) << (m - 1))) % 2
xor = bit + u - 2 * bit * u
prod = xor * r[-1]
# u_prime = xor * u + (1 - xor) * r[-1]
u_prime = bit * u + u - 2 * bit * u + r[-1] - prod
a_prime = (c % (cint(1) << m)) - r_prime + (cint(1) << m) * u_prime
d = (a - a_prime) / (cint(1) << m)
rounding = xor + r[-1] - 2 * prod
return d + rounding
def TruncRoundNearest(a, k, m, kappa):
"""
Returns a / 2^m, rounded to the nearest integer.
k: bit length of m
m: compile-time integer
"""
from types import sint, cint
from library import reveal, load_int_to_secret
if m == 1:
if program.options.ring:
lsb = Mod2mRing(None, a, k, 1, False)
return TruncRing(None, a + lsb, k + 1, 1, False)
else:
lsb = sint()
Mod2(lsb, a, k, kappa, False)
return (a + lsb) / 2
r_dprime = sint()
r_prime = sint()
r = [sint() for i in range(m)]
u = sint()
PRandM(r_dprime, r_prime, r, k, m, kappa)
c = reveal((cint(1) << (k - 1)) + a + (cint(1) << m) * r_dprime + r_prime)
c_prime = c % (cint(1) << (m - 1))
if const_rounds:
BitLTC1(u, c_prime, r[:-1], kappa)
else:
BitLTL(u, c_prime, r[:-1], kappa)
bit = ((c - c_prime) >> (m - 1)) % 2
xor = bit + u - 2 * bit * u
prod = xor * r[-1]
# u_prime = xor * u + (1 - xor) * r[-1]
u_prime = bit * u + u - 2 * bit * u + r[-1] - prod
a_prime = (c % (cint(1) << m)) - r_prime + (cint(1) << m) * u_prime
d = (a - a_prime) >> m
rounding = xor + r[-1] - 2 * prod
return d + rounding