# HG changeset patch
# User Janus Dam Nielsen <janus.niel...@alexandra.dk>
# Date 1245394849 -7200
# Node ID f780a9ea514acb7de9d70022a8845938599696c8
# Parent 15c0283f7cb6dad3d7a41e9095bb4fd18a30d909
Implemented secret sharing command.
diff --git a/viff/orlandi.py b/viff/orlandi.py
--- a/viff/orlandi.py
+++ b/viff/orlandi.py
@@ -67,3 +67,112 @@
"""Initialize runtime."""
Runtime.__init__(self, player, threshold, options)
self.threshold = self.num_players - 1
+
+ def _Com(self, x, rho):
+ return x + rho[0] + rho[1]
+
+ def output(self, share, receivers=None, threshold=None):
+ return self.open(share, receivers, threshold)
+
+ def _send_orlandi_share(self, other_id, pc, xi, rhoi, Cx):
+ """Send the share xim, rhoi, and the commitment Cx to party
other_id."""
+ self.protocols[other_id].sendShare(pc, xi)
+ self.protocols[other_id].sendShare(pc, rhoi[0])
+ self.protocols[other_id].sendShare(pc, rhoi[1])
+ self.protocols[other_id].sendShare(pc, Cx)
+
+ def _expect_orlandi_share(self, peer_id, field):
+ """Waits for a number x, rho, and the commitment for x. """
+ xi = self._expect_share(peer_id, field)
+ rhoi1 = self._expect_share(peer_id, field)
+ rhoi2 = self._expect_share(peer_id, field)
+ Cx = self._expect_share(peer_id, field)
+ sls = ShareList([xi, rhoi1, rhoi2, Cx])
+ def combine(ls):
+ if len(ls) is not 4:
+ raise OrlandiException("Cannot share number, trying to create
share," + \
+ " but there are too few or too many
components.")
+ s1, xi = ls[0]
+ s2, rhoi1 = ls[1]
+ s3, rhoi2 = ls[2]
+ s4, Cx = ls[3]
+ if not (s1 and s2 and s3 and s4):
+ raise OrlandiException("Cannot share number, trying to create
share," + \
+ " but a component did arrive
properly.")
+ return OrlandiShare(self, field, xi, (rhoi1, rhoi2), Cx)
+ sls.addCallbacks(combine, self.error_handler)
+ return sls
+
+ @increment_pc
+ def secret_share(self, inputters, field, number=None, threshold=None):
+ """Share the value, number, among all the parties using additive
shareing.
+
+ To share an element x in Z_{p}, choose random x_{1}, ..., x_{n-1} in
Z_{p},
+ define x_{n} = x - SUM_{i=1}^{n-1} x_{i} mod p.
+ Choose random values rho_{x,1}, ..., rho_{x,n} in (Z_{p})^2, define
+ rho_x = SUM_{i=1}^{n} rho_{x,i} and C_{x} = Com_{ck}(x, p_{x}).
+
+ Send [x]_{i} = (x_{i}, rho_{x,i}, C_{x}) to party P_{i}.
+ """
+ assert number is None or self.id in inputters
+ self.threshold = self.num_players - 1
+
+ def additive_shares_with_rho(x):
+ """Returns a tuple of a list of tuples (player id, share, rho) and
rho.
+
+ Chooses random elements x_{1}, ..., x_{n-1} in field and x_{n} st.
+ x_{n} = x - Sum_{i=1}^{n-1} x_{i}.
+ Chooses random pair of elements rho_{1}, ..., rho_{n} in field_{2}
+ and define rho_{n} = Sum_{i=1}^{n} rho_{i}.
+ Returns a pair of ((player id, x_{i}, rho_{i}), rho).
+ """
+ shares = []
+ rhos = []
+ sum = field(0)
+ rho1 = field(0)
+ rho2 = field(0)
+ for i in xrange(1, self.num_players):
+ xi = field(rand.randint(0, field.modulus - 1))
+ rhoi1 = field(rand.randint(0, field.modulus - 1))
+ rhoi2 = field(rand.randint(0, field.modulus - 1))
+ sum += xi
+ rho1 += rhoi1
+ rho2 += rhoi2
+ shares.append((i, xi, (rhoi1, rhoi2)))
+ xn = field(x) - sum
+ rhon1 = field(rand.randint(0, field.modulus - 1))
+ rhon2 = field(rand.randint(0, field.modulus - 1))
+ shares.append((self.num_players, xn, (rhon1, rhon2)))
+ rho1 += rhon1
+ rho2 += rhon2
+ return shares, (rho1, rho2)
+
+ # Send [x]_{i} = (x_{i}, rho_{x,i}, C_{x}) to party P_{i}.
+ results = []
+ for peer_id in inputters:
+ if peer_id == self.id:
+ pc = tuple(self.program_counter)
+ shares, rho = additive_shares_with_rho(number)
+ Cx = self._Com(number, rho)
+ # Distribute the shares
+ for other_id, xi, rhoi in shares:
+ if other_id == self.id:
+ results.append(OrlandiShare(self, field, xi, rhoi, Cx))
+ else:
+ # Send xi, rhoi, and commitment
+ self._send_orlandi_share(other_id, pc, xi, rhoi, Cx)
+ else:
+ # Expect xi, rhoi, and commitment
+ results.append(self._expect_orlandi_share(peer_id, field))
+
+ # do actual communication
+ self.activate_reactor()
+
+ # Unpack a singleton list.
+ if len(results) == 1:
+ return results[0]
+ return results
+
+ def error_handler(self, ex):
+ print "Error: ", ex
+ return ex
diff --git a/viff/test/test_orlandi_runtime.py
b/viff/test/test_orlandi_runtime.py
--- a/viff/test/test_orlandi_runtime.py
+++ b/viff/test/test_orlandi_runtime.py
@@ -31,3 +31,21 @@
num_players = 3
runtime_class = OrlandiRuntime
+
+ @protocol
+ def test_secret_share(self, runtime):
+ """Test sharing of random numbers."""
+
+ def check((xi, (rho1, rho2), Cr)):
+ # Check that we got the expected number of shares.
+ self.assert_type(xi, FieldElement)
+ self.assert_type(rho1, FieldElement)
+ self.assert_type(rho2, FieldElement)
+ self.assert_type(Cr, FieldElement)
+
+ if 1 == runtime.id:
+ share = runtime.secret_share([1], self.Zp, 42)
+ else:
+ share = runtime.secret_share([1], self.Zp)
+ share.addCallback(check)
+ return share
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