def check_positive(self, bits=None):
"""
Checks if a LinComb is a positive bitlength-bit integer
Costs bitlength + 2 constraints
"""
from pysnark.boolean import PrivValBool
if bits is None:
bits = bitlength
if is_guard() and self.value.bit_length() <= bits:
ret = PrivValBool(1 if self.value >= 0 else 0)
abs = self.value if self.value >= 0 else -self.value
bits = [PrivValBool((abs & (1 << ix)) >> ix) for ix in range(bits)]
elif ignore_errors():
ret = PrivValBool(0)
bits = [PrivValBool(0) for _ in range(bits)]
else:
raise ValueError(
str(self.value) + " is not a " + str(bits) + "-bit integer")
# If ret == 1, then requires that 2 * self = self + sum, so sum = self
# If ret == 0, this requires that 0 = self + sum, so sum = -self
add_constraint(2 * ret, self, self + LinComb.from_bits(bits))
return ret
def test_mixed_branch(self):
assert if_then_else(PrivValBool(0), PrivVal(1),
PrivValFxp(2.5)).val() == 2.5
assert if_then_else(PrivValBool(1), PrivValFxp(1.5),
PrivValBool(1)).val() == 1.5
assert if_then_else(PrivValBool(1), PrivValBool(1),
PrivVal(2)).val() == 1
def to_bits(self, bits=None):
"""
Splits an integer LinComb into an bitlength-length array of LinCombBool bits
Raises AssertionError if LinComb cannot be represented with bitlength bits
Costs bitlength + 1 constraints to split a LinComb into bits
"""
from pysnark.boolean import PrivValBool
if bits is None:
bits = bitlength
if not ignore_errors():
if self.value < 0 or self.value.bit_length() > bits:
raise AssertionError(
str(self.value) + " is not a " + str(bits) +
"-bit positive integer")
# Construct bits
bits = [
PrivValBool((self.value & (1 << ix)) >> ix) for ix in range(bits)
]
# Check that bits are equal to self
(self - LinComb.from_bits(bits)).assert_zero()
return bits
def test_mul(self):
assert (PrivValBool(1) * PrivValBool(0)).val() == 0
assert (PrivVal(2) * PrivValBool(0)).val() == 0
assert (PrivValBool(0) * PrivVal(2)).val() == 0
assert (PrivVal(2) * PrivValBool(1)).val() == 2
assert (PrivValBool(1) * PrivVal(2)).val() == 2
assert (2 * PrivValBool(1)).val() == 2
assert (PrivValBool(1) * 2).val() == 2
def test_sub(self):
assert (PrivValBool(1) - PrivValBool(1)).val() == 0
assert (PrivVal(1) - PrivValBool(1)).val() == 0
assert (PrivValBool(1) - PrivVal(1)).val() == 0
assert (1 - PrivValBool(1)).val() == 0
assert (PrivValBool(1) - 1).val() == 0
def test_add(self):
assert (PrivValBool(1) + PrivValBool(1)).val() == 2
assert (PrivVal(1) + PrivValBool(1)).val() == 2
assert (PrivValBool(1) + PrivVal(1)).val() == 2
assert (1 + PrivValBool(1)).val() == 2
assert (PrivValBool(1) + 1).val() == 2
def test_priv_val(self):
assert PrivValBool(0).val() == 0
assert PrivValBool(1).val() == 1
def test_lincombbool(self):
from pysnark.poseidon_hash import poseidon_hash
poseidon_hash([PrivValBool(0), PrivValBool(1), PrivValBool(0), PrivValBool(1), PrivValBool(0)])
def test_lincomb_branch(self):
assert if_then_else(PrivValBool(0), PrivVal(1), PrivVal(2)).val() == 2
assert if_then_else(PrivValBool(1), PrivVal(1), PrivVal(2)).val() == 1
def test_lincombfxp_branch(self):
assert if_then_else(PrivValBool(0), PrivValFxp(1.5),
PrivValFxp(2.5)).val() == 2.5
assert if_then_else(PrivValBool(1), PrivValFxp(1.5),
PrivValFxp(2.5)).val() == 1.5