def BitDecFullBig(a):
from Compiler.types import sint, regint
from Compiler.library import do_while
p=program.P
bit_length = p.bit_length()
abits = [sint(0)]*bit_length
bbits = [sint(0)]*bit_length
pbits = list(bits(p,bit_length+1))
# Loop until we get some random integers less than p
@do_while
def get_bits_loop():
# How can we do this with a vectorized load of the bits? XXXX
tbits = [sint(0)]*bit_length
for i in range(bit_length):
tbits[i] = sint.get_random_bit()
tbits[i].store_in_mem(i)
c = regint(BitLTFull(tbits, pbits, bit_length).reveal())
return (c!=1)
for i in range(bit_length):
bbits[i]=sint.load_mem(i)
b = SumBits(bbits, bit_length)
c = (a-b).reveal()
czero = (c==0)
d = BitAdd(list(bits(c,bit_length)), bbits)
q = BitLTFull( pbits, d, bit_length+1)
f = list(bits((1<<bit_length)-p,bit_length))
g = [sint(0)]*(bit_length+1)
for i in range(bit_length):
g[i]=f[i]*q;
h = BitAdd(d, g)
for i in range(bit_length):
abits[i] = (1-czero)*h[i]+czero*bbits[i]
return abits
def BitDecFull(a):
from Compiler.types import sint, regint
from Compiler.library import do_while
p = program.P
bit_length = p.bit_length()
if bit_length > 63:
return BitDecFullBig(a)
abits = [sint(0)] * bit_length
bbits = [sint(0)] * bit_length
pbits = list(bits(p, bit_length))
# Loop until we get some random integers less than p
@do_while
def get_bits_loop():
# How can we do this with a vectorized load of the bits? XXXX
tbits = [sint(0)] * bit_length
for i in range(bit_length):
tbits[i] = sint.get_random_bit()
tbits[i].store_in_mem(i)
c = regint(BitLTFull(tbits, pbits, bit_length).reveal())
return (c != 1)
for i in range(bit_length):
bbits[i] = sint.load_mem(i)
b = SumBits(bbits, bit_length)
# Reveal c in the correct range
c = regint((a - b).reveal())
bit = c < 0
c = c + p * bit
czero = (c == 0)
t = (p - c).bit_decompose(bit_length)
q = 1 - BitLTFull(bbits, t, bit_length)
fbar = ((1 << bit_length) + c - p).bit_decompose(bit_length)
fbard = regint(c).bit_decompose(bit_length)
g = [sint(0)] * (bit_length)
for i in range(bit_length):
g[i] = (fbar[i] - fbard[i]) * q + fbard[i]
h = BitAdd(bbits, g)
for i in range(bit_length):
abits[i] = (1 - czero) * h[i] + czero * bbits[i]
return abits
def load_secret_mem(address):
return sint.load_mem(address)
def load_secret_mem(address):
return sint.load_mem(address)
