Dear Ivan,
Yes I know about that. But 367 is 3 mod 4 so it should be OK. And the existing
protocol works with 367 only if the two numbers are not equal. If they are, I
got the error mentioned in my first message.
If I can solve the error in the existing protocol, I will be able to continue
my work.
Thank you for your answer,
Jonathan
Le 8 avr. 2010 à 16:26, Ivan Damgård a écrit :
Dear Jonathan,
You cannot expect the protocol to work for primes that are 1 mod 4,
it is based on the fact that for primes p that are 3 mod 4, you can
deterministically
compute a square root mod p by raising to power (p+1)/4.
This does not work if p is 1 mod 4.
regards, Ivan
On 08/04/2010, at 14.11, Jonathan Van den Schrieck wrote:
Hello,
I am trying to modify the equality protocol to make it work for primes
congruent to 5 mod 8 (exists for Blum primes).
The problem is that I have an error with the original protocol. It works
perfectly with p = 211 for example. But for p = 367, it doesn't.
Here is the code I'm using to test it :
from optparse import OptionParser
import viff.reactor
viff.reactor.install()
from twisted.internet import reactor
from viff.field import GF
from viff.runtime import create_runtime, gather_shares
from viff.passive import PassiveRuntime
from viff.equality_ohta import ProbabilisticEqualityMixin2
from viff.equality import ProbabilisticEqualityMixin
from viff.comparison import Toft05Runtime
from viff.config import load_config
from viff.util import rand, find_prime
class EqualityRuntime(PassiveRuntime, ProbabilisticEqualityMixin):
Default mix of :class:`~viff.equality.ProbabilisticEqualityMixin`
and :class:`~viff.passive.PassiveRuntime`.
pass
class Protocol:
def __init__(self, runtime):
# Save the Runtime for later use
self.runtime = runtime
k = runtime.options.security_parameter
print security parameter = , k
Zp = GF(367)
# We must secret share our input with the other parties. They
# will do the same and we end up with three variables
# input is equal to the player id
rand = runtime.prss_share_random(Zp)
#rand1 = runtime.prss_share_random(Zp)
rand1 = rand
print rand = , rand, rand1 = , rand1
#open rand and rand1 to print their value
open_rand = runtime.open(rand)
open_rand1 = runtime.open(rand1)
temp = gather_shares([open_rand, open_rand1])
temp.addCallback(self.results_ready)
# we test if rand == rand1 by using equality protocol
test = (rand == rand1)
test_open = runtime.open(test)
results = gather_shares([test_open])
results.addCallback(self.results_ready)
runtime.schedule_callback(results, lambda _: runtime.synchronize())
runtime.schedule_callback(results, lambda _: runtime.shutdown())
def results_ready(self, results):
print ALGO_QUAD temp results =, results
def mtemp(self, temp):
print local part of shares after callback =
print temp
# Parse command line arguments.
parser = OptionParser()
EqualityRuntime.add_options(parser)
options, args = parser.parse_args()
if len(args) == 0:
parser.error(you must specify a config file)
else:
id, players = load_config(args[0])
# Create a deferred Runtime and ask it to run our protocol when ready.
pre_runtime = create_runtime(id, players, 1, options, EqualityRuntime)
pre_runtime.addCallback(Protocol)
# Start the Twisted event loop.
reactor.run()
as you can see, I simply generate 2 random numbers, then I test if they have
the same value, and I print the result of the test.
This will work if rand != rand1, but if I set rand1 = rand = ERROR.
This error will only happen if p = 367 (and maybe with others primes, but I
couldn't test them all)
Here is the error :
Unhandled error in Deferred:
Traceback (most recent call last):
File
/System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/twisted/internet/defer.py,
line 328, in _runCallbacks
self.result = callback(self.result, *args, **kw)
File /Users/jonathanvds/opt/lib/python/viff/runtime.py, line 239, in
_callback_fired
self.callback(self.results)
File
/System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/twisted/internet/defer.py,
line 243, in callback
self._startRunCallbacks(result)
File
/System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/twisted/internet/defer.py,
line 312, in _startRunCallbacks
self._runCallbacks()
--- exception caught here ---
File
/System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/twisted/internet/defer.py,
line 328, in _runCallbacks
self.result = callback(self.result, *args, **kw)
File /Users/jonathanvds/opt/lib/python/viff/passive.py,
