def maskField(a, k, kappa):
r_dprime = types.sint()
r_prime = types.sint()
c = types.cint()
r = [types.sint() for i in range(k)]
comparison.PRandM(r_dprime, r_prime, r, k, k, kappa)
asm_open(c, a + two_power(k) * r_dprime + r_prime) # + 2**(k-1))
return c, r
def EQZ(a, k, kappa):
r_dprime = types.sint()
r_prime = types.sint()
c = types.cint()
d = [None] * k
r = [types.sint() for i in range(k)]
comparison.PRandM(r_dprime, r_prime, r, k, k, kappa)
asm_open(c, a + two_power(k) * r_dprime + r_prime) # + 2**(k-1))
for i, b in enumerate(bits(c, k)):
d[i] = b + r[i] - 2 * b * r[i]
return 1 - KOR(d, kappa)
def TruncPrField(a, k, m, kappa=None):
if kappa is None:
kappa = 40
b = two_power(k-1) + a
r_prime, r_dprime = types.sint(), types.sint()
comparison.PRandM(r_dprime, r_prime, [types.sint() for i in range(m)],
k, m, kappa)
two_to_m = two_power(m)
r = two_to_m * r_dprime + r_prime
c = (b + r).reveal()
c_prime = c % two_to_m
a_prime = c_prime - r_prime
d = (a - a_prime) / two_to_m
return d
def TruncPr(a, k, m, kappa=None):
""" Probabilistic truncation [a/2^m + u]
where Pr[u = 1] = (a % 2^m) / 2^m
"""
if kappa is None:
kappa = 40
b = two_power(k-1) + a
r_prime, r_dprime = types.sint(), types.sint()
comparison.PRandM(r_dprime, r_prime, [types.sint() for i in range(m)],
k, m, kappa)
two_to_m = two_power(m)
r = two_to_m * r_dprime + r_prime
c = (b + r).reveal()
c_prime = c % two_to_m
a_prime = c_prime - r_prime
d = (a - a_prime) / two_to_m
return d
def BitDec(a, k, m, kappa, bits_to_compute=None):
r_dprime = types.sint()
r_prime = types.sint()
c = types.cint()
r = [types.sint() for i in range(m)]
comparison.PRandM(r_dprime, r_prime, r, k, m, kappa)
#assert(r_prime.value == sum(r[i].value*2**i for i in range(m)) % comparison.program.P)
pow2 = two_power(k + kappa)
asm_open(c, pow2 + two_power(k) + a - two_power(m) * r_dprime - r_prime)
#rval = 2**m*r_dprime.value + r_prime.value
#assert(rval % 2**m == r_prime.value)
#assert(rval == (2**m*r_dprime.value + sum(r[i].value*2**i for i in range(m)) % comparison.program.P ))
try:
pass #assert(c.value == (2**(k + kappa) + 2**k + (a.value%2**k) - rval) % comparison.program.P)
except AssertionError:
print 'BitDec assertion failed'
print 'a =', a.value
print 'a mod 2^%d =' % k, (a.value % 2**k)
return BitAdd(list(bits(c, m)), r, bits_to_compute)[:-1]
