Consolidate external libraries

This commit is contained in:
Pretty Printer
2024-03-21 21:29:31 -05:00
committed by John Freeman
parent dd312c3cc5
commit e2384885f5
184 changed files with 13 additions and 40 deletions

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load("secp256k1_params.sage")
MAX_ORDER = 1000
# Set of (curve) orders we have encountered so far.
orders_done = set()
# Map from (subgroup) orders to [b, int(gen.x), int(gen.y), gen, lambda] for those subgroups.
solutions = {}
# Iterate over curves of the form y^2 = x^3 + B.
for b in range(1, P):
# There are only 6 curves (up to isomorphism) of the form y^2 = x^3 + B. Stop once we have tried all.
if len(orders_done) == 6:
break
E = EllipticCurve(F, [0, b])
print("Analyzing curve y^2 = x^3 + %i" % b)
n = E.order()
# Skip curves with an order we've already tried
if n in orders_done:
print("- Isomorphic to earlier curve")
print()
continue
orders_done.add(n)
# Skip curves isomorphic to the real secp256k1
if n.is_pseudoprime():
assert E.is_isomorphic(C)
print("- Isomorphic to secp256k1")
print()
continue
print("- Finding prime subgroups")
# Map from group_order to a set of independent generators for that order.
curve_gens = {}
for g in E.gens():
# Find what prime subgroups of group generated by g exist.
g_order = g.order()
for f, _ in g.order().factor():
# Skip subgroups that have bad size.
if f < 4:
print(f" - Subgroup of size {f}: too small")
continue
if f > MAX_ORDER:
print(f" - Subgroup of size {f}: too large")
continue
# Construct a generator for that subgroup.
gen = g * (g_order // f)
assert(gen.order() == f)
# Add to set the minimal multiple of gen.
curve_gens.setdefault(f, set()).add(min([j*gen for j in range(1, f)]))
print(f" - Subgroup of size {f}: ok")
for f in sorted(curve_gens.keys()):
print(f"- Constructing group of order {f}")
cbrts = sorted([int(c) for c in Integers(f)(1).nth_root(3, all=true) if c != 1])
gens = list(curve_gens[f])
sol_count = 0
no_endo_count = 0
# Consider all non-zero linear combinations of the independent generators.
for j in range(1, f**len(gens)):
gen = sum(gens[k] * ((j // f**k) % f) for k in range(len(gens)))
assert not gen.is_zero()
assert (f*gen).is_zero()
# Find lambda for endomorphism. Skip if none can be found.
lam = None
for l in cbrts:
if l*gen == E(BETA*gen[0], gen[1]):
lam = l
break
if lam is None:
no_endo_count += 1
else:
sol_count += 1
solutions.setdefault(f, []).append((b, int(gen[0]), int(gen[1]), gen, lam))
print(f" - Found {sol_count} generators (plus {no_endo_count} without endomorphism)")
print()
def output_generator(g, name):
print(f"#define {name} SECP256K1_GE_CONST(\\")
print(" 0x%08x, 0x%08x, 0x%08x, 0x%08x,\\" % tuple((int(g[0]) >> (32 * (7 - i))) & 0xffffffff for i in range(4)))
print(" 0x%08x, 0x%08x, 0x%08x, 0x%08x,\\" % tuple((int(g[0]) >> (32 * (7 - i))) & 0xffffffff for i in range(4, 8)))
print(" 0x%08x, 0x%08x, 0x%08x, 0x%08x,\\" % tuple((int(g[1]) >> (32 * (7 - i))) & 0xffffffff for i in range(4)))
print(" 0x%08x, 0x%08x, 0x%08x, 0x%08x\\" % tuple((int(g[1]) >> (32 * (7 - i))) & 0xffffffff for i in range(4, 8)))
print(")")
def output_b(b):
print(f"#define SECP256K1_B {int(b)}")
print()
print("To be put in src/group_impl.h:")
print()
print("/* Begin of section generated by sage/gen_exhaustive_groups.sage. */")
for f in sorted(solutions.keys()):
# Use as generator/2 the one with lowest b, and lowest (x, y) generator (interpreted as non-negative integers).
b, _, _, HALF_G, lam = min(solutions[f])
output_generator(2 * HALF_G, f"SECP256K1_G_ORDER_{f}")
print("/** Generator for secp256k1, value 'g' defined in")
print(" * \"Standards for Efficient Cryptography\" (SEC2) 2.7.1.")
print(" */")
output_generator(G, "SECP256K1_G")
print("/* These exhaustive group test orders and generators are chosen such that:")
print(" * - The field size is equal to that of secp256k1, so field code is the same.")
print(" * - The curve equation is of the form y^2=x^3+B for some small constant B.")
print(" * - The subgroup has a generator 2*P, where P.x is as small as possible.")
print(f" * - The subgroup has size less than {MAX_ORDER} to permit exhaustive testing.")
print(" * - The subgroup admits an endomorphism of the form lambda*(x,y) == (beta*x,y).")
print(" */")
print("#if defined(EXHAUSTIVE_TEST_ORDER)")
first = True
for f in sorted(solutions.keys()):
b, _, _, _, lam = min(solutions[f])
print(f"# {'if' if first else 'elif'} EXHAUSTIVE_TEST_ORDER == {f}")
first = False
print()
print(f"static const secp256k1_ge secp256k1_ge_const_g = SECP256K1_G_ORDER_{f};")
output_b(b)
print()
print("# else")
print("# error No known generator for the specified exhaustive test group order.")
print("# endif")
print("#else")
print()
print("static const secp256k1_ge secp256k1_ge_const_g = SECP256K1_G;")
output_b(7)
print()
print("#endif")
print("/* End of section generated by sage/gen_exhaustive_groups.sage. */")
print()
print()
print("To be put in src/scalar_impl.h:")
print()
print("/* Begin of section generated by sage/gen_exhaustive_groups.sage. */")
first = True
for f in sorted(solutions.keys()):
_, _, _, _, lam = min(solutions[f])
print("# %s EXHAUSTIVE_TEST_ORDER == %i" % ("if" if first else "elif", f))
first = False
print("# define EXHAUSTIVE_TEST_LAMBDA %i" % lam)
print("# else")
print("# error No known lambda for the specified exhaustive test group order.")
print("# endif")
print("/* End of section generated by sage/gen_exhaustive_groups.sage. */")

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""" Generates the constants used in secp256k1_scalar_split_lambda.
See the comments for secp256k1_scalar_split_lambda in src/scalar_impl.h for detailed explanations.
"""
load("secp256k1_params.sage")
def inf_norm(v):
"""Returns the infinity norm of a vector."""
return max(map(abs, v))
def gauss_reduction(i1, i2):
v1, v2 = i1.copy(), i2.copy()
while True:
if inf_norm(v2) < inf_norm(v1):
v1, v2 = v2, v1
# This is essentially
# m = round((v1[0]*v2[0] + v1[1]*v2[1]) / (inf_norm(v1)**2))
# (rounding to the nearest integer) without relying on floating point arithmetic.
m = ((v1[0]*v2[0] + v1[1]*v2[1]) + (inf_norm(v1)**2) // 2) // (inf_norm(v1)**2)
if m == 0:
return v1, v2
v2[0] -= m*v1[0]
v2[1] -= m*v1[1]
def find_split_constants_gauss():
"""Find constants for secp256k1_scalar_split_lamdba using gauss reduction."""
(v11, v12), (v21, v22) = gauss_reduction([0, N], [1, int(LAMBDA)])
# We use related vectors in secp256k1_scalar_split_lambda.
A1, B1 = -v21, -v11
A2, B2 = v22, -v21
return A1, B1, A2, B2
def find_split_constants_explicit_tof():
"""Find constants for secp256k1_scalar_split_lamdba using the trace of Frobenius.
See Benjamin Smith: "Easy scalar decompositions for efficient scalar multiplication on
elliptic curves and genus 2 Jacobians" (https://eprint.iacr.org/2013/672), Example 2
"""
assert P % 3 == 1 # The paper says P % 3 == 2 but that appears to be a mistake, see [10].
assert C.j_invariant() == 0
t = C.trace_of_frobenius()
c = Integer(sqrt((4*P - t**2)/3))
A1 = Integer((t - c)/2 - 1)
B1 = c
A2 = Integer((t + c)/2 - 1)
B2 = Integer(1 - (t - c)/2)
# We use a negated b values in secp256k1_scalar_split_lambda.
B1, B2 = -B1, -B2
return A1, B1, A2, B2
A1, B1, A2, B2 = find_split_constants_explicit_tof()
# For extra fun, use an independent method to recompute the constants.
assert (A1, B1, A2, B2) == find_split_constants_gauss()
# PHI : Z[l] -> Z_n where phi(a + b*l) == a + b*lambda mod n.
def PHI(a,b):
return Z(a + LAMBDA*b)
# Check that (A1, B1) and (A2, B2) are in the kernel of PHI.
assert PHI(A1, B1) == Z(0)
assert PHI(A2, B2) == Z(0)
# Check that the parallelogram generated by (A1, A2) and (B1, B2)
# is a fundamental domain by containing exactly N points.
# Since the LHS is the determinant and N != 0, this also checks that
# (A1, A2) and (B1, B2) are linearly independent. By the previous
# assertions, (A1, A2) and (B1, B2) are a basis of the kernel.
assert A1*B2 - B1*A2 == N
# Check that their components are short enough.
assert (A1 + A2)/2 < sqrt(N)
assert B1 < sqrt(N)
assert B2 < sqrt(N)
G1 = round((2**384)*B2/N)
G2 = round((2**384)*(-B1)/N)
def rnddiv2(v):
if v & 1:
v += 1
return v >> 1
def scalar_lambda_split(k):
"""Equivalent to secp256k1_scalar_lambda_split()."""
c1 = rnddiv2((k * G1) >> 383)
c2 = rnddiv2((k * G2) >> 383)
c1 = (c1 * -B1) % N
c2 = (c2 * -B2) % N
r2 = (c1 + c2) % N
r1 = (k + r2 * -LAMBDA) % N
return (r1, r2)
# The result of scalar_lambda_split can depend on the representation of k (mod n).
SPECIAL = (2**383) // G2 + 1
assert scalar_lambda_split(SPECIAL) != scalar_lambda_split(SPECIAL + N)
print(' A1 =', hex(A1))
print(' -B1 =', hex(-B1))
print(' A2 =', hex(A2))
print(' -B2 =', hex(-B2))
print(' =', hex(Z(-B2)))
print(' -LAMBDA =', hex(-LAMBDA))
print(' G1 =', hex(G1))
print(' G2 =', hex(G2))

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# This code supports verifying group implementations which have branches
# or conditional statements (like cmovs), by allowing each execution path
# to independently set assumptions on input or intermediary variables.
#
# The general approach is:
# * A constraint is a tuple of two sets of symbolic expressions:
# the first of which are required to evaluate to zero, the second of which
# are required to evaluate to nonzero.
# - A constraint is said to be conflicting if any of its nonzero expressions
# is in the ideal with basis the zero expressions (in other words: when the
# zero expressions imply that one of the nonzero expressions are zero).
# * There is a list of laws that describe the intended behaviour, including
# laws for addition and doubling. Each law is called with the symbolic point
# coordinates as arguments, and returns:
# - A constraint describing the assumptions under which it is applicable,
# called "assumeLaw"
# - A constraint describing the requirements of the law, called "require"
# * Implementations are transliterated into functions that operate as well on
# algebraic input points, and are called once per combination of branches
# executed. Each execution returns:
# - A constraint describing the assumptions this implementation requires
# (such as Z1=1), called "assumeFormula"
# - A constraint describing the assumptions this specific branch requires,
# but which is by construction guaranteed to cover the entire space by
# merging the results from all branches, called "assumeBranch"
# - The result of the computation
# * All combinations of laws with implementation branches are tried, and:
# - If the combination of assumeLaw, assumeFormula, and assumeBranch results
# in a conflict, it means this law does not apply to this branch, and it is
# skipped.
# - For others, we try to prove the require constraints hold, assuming the
# information in assumeLaw + assumeFormula + assumeBranch, and if this does
# not succeed, we fail.
# + To prove an expression is zero, we check whether it belongs to the
# ideal with the assumed zero expressions as basis. This test is exact.
# + To prove an expression is nonzero, we check whether each of its
# factors is contained in the set of nonzero assumptions' factors.
# This test is not exact, so various combinations of original and
# reduced expressions' factors are tried.
# - If we succeed, we print out the assumptions from assumeFormula that
# weren't implied by assumeLaw already. Those from assumeBranch are skipped,
# as we assume that all constraints in it are complementary with each other.
#
# Based on the sage verification scripts used in the Explicit-Formulas Database
# by Tanja Lange and others, see https://hyperelliptic.org/EFD
class fastfrac:
"""Fractions over rings."""
def __init__(self,R,top,bot=1):
"""Construct a fractional, given a ring, a numerator, and denominator."""
self.R = R
if parent(top) == ZZ or parent(top) == R:
self.top = R(top)
self.bot = R(bot)
elif top.__class__ == fastfrac:
self.top = top.top
self.bot = top.bot * bot
else:
self.top = R(numerator(top))
self.bot = R(denominator(top)) * bot
def iszero(self,I):
"""Return whether this fraction is zero given an ideal."""
return self.top in I and self.bot not in I
def reduce(self,assumeZero):
zero = self.R.ideal(list(map(numerator, assumeZero)))
return fastfrac(self.R, zero.reduce(self.top)) / fastfrac(self.R, zero.reduce(self.bot))
def __add__(self,other):
"""Add two fractions."""
if parent(other) == ZZ:
return fastfrac(self.R,self.top + self.bot * other,self.bot)
if other.__class__ == fastfrac:
return fastfrac(self.R,self.top * other.bot + self.bot * other.top,self.bot * other.bot)
return NotImplemented
def __sub__(self,other):
"""Subtract two fractions."""
if parent(other) == ZZ:
return fastfrac(self.R,self.top - self.bot * other,self.bot)
if other.__class__ == fastfrac:
return fastfrac(self.R,self.top * other.bot - self.bot * other.top,self.bot * other.bot)
return NotImplemented
def __neg__(self):
"""Return the negation of a fraction."""
return fastfrac(self.R,-self.top,self.bot)
def __mul__(self,other):
"""Multiply two fractions."""
if parent(other) == ZZ:
return fastfrac(self.R,self.top * other,self.bot)
if other.__class__ == fastfrac:
return fastfrac(self.R,self.top * other.top,self.bot * other.bot)
return NotImplemented
def __rmul__(self,other):
"""Multiply something else with a fraction."""
return self.__mul__(other)
def __truediv__(self,other):
"""Divide two fractions."""
if parent(other) == ZZ:
return fastfrac(self.R,self.top,self.bot * other)
if other.__class__ == fastfrac:
return fastfrac(self.R,self.top * other.bot,self.bot * other.top)
return NotImplemented
# Compatibility wrapper for Sage versions based on Python 2
def __div__(self,other):
"""Divide two fractions."""
return self.__truediv__(other)
def __pow__(self,other):
"""Compute a power of a fraction."""
if parent(other) == ZZ:
if other < 0:
# Negative powers require flipping top and bottom
return fastfrac(self.R,self.bot ^ (-other),self.top ^ (-other))
else:
return fastfrac(self.R,self.top ^ other,self.bot ^ other)
return NotImplemented
def __str__(self):
return "fastfrac((" + str(self.top) + ") / (" + str(self.bot) + "))"
def __repr__(self):
return "%s" % self
def numerator(self):
return self.top
class constraints:
"""A set of constraints, consisting of zero and nonzero expressions.
Constraints can either be used to express knowledge or a requirement.
Both the fields zero and nonzero are maps from expressions to description
strings. The expressions that are the keys in zero are required to be zero,
and the expressions that are the keys in nonzero are required to be nonzero.
Note that (a != 0) and (b != 0) is the same as (a*b != 0), so all keys in
nonzero could be multiplied into a single key. This is often much less
efficient to work with though, so we keep them separate inside the
constraints. This allows higher-level code to do fast checks on the individual
nonzero elements, or combine them if needed for stronger checks.
We can't multiply the different zero elements, as it would suffice for one of
the factors to be zero, instead of all of them. Instead, the zero elements are
typically combined into an ideal first.
"""
def __init__(self, **kwargs):
if 'zero' in kwargs:
self.zero = dict(kwargs['zero'])
else:
self.zero = dict()
if 'nonzero' in kwargs:
self.nonzero = dict(kwargs['nonzero'])
else:
self.nonzero = dict()
def negate(self):
return constraints(zero=self.nonzero, nonzero=self.zero)
def map(self, fun):
return constraints(zero={fun(k): v for k, v in self.zero.items()}, nonzero={fun(k): v for k, v in self.nonzero.items()})
def __add__(self, other):
zero = self.zero.copy()
zero.update(other.zero)
nonzero = self.nonzero.copy()
nonzero.update(other.nonzero)
return constraints(zero=zero, nonzero=nonzero)
def __str__(self):
return "constraints(zero=%s,nonzero=%s)" % (self.zero, self.nonzero)
def __repr__(self):
return "%s" % self
def normalize_factor(p):
"""Normalizes the sign of primitive polynomials (as returned by factor())
This function ensures that the polynomial has a positive leading coefficient.
This is necessary because recent sage versions (starting with v9.3 or v9.4,
we don't know) are inconsistent about the placement of the minus sign in
polynomial factorizations:
```
sage: R.<ax,bx,ay,by,Az,Bz,Ai,Bi> = PolynomialRing(QQ,8,order='invlex')
sage: R((-2 * (bx - ax)) ^ 1).factor()
(-2) * (bx - ax)
sage: R((-2 * (bx - ax)) ^ 2).factor()
(4) * (-bx + ax)^2
sage: R((-2 * (bx - ax)) ^ 3).factor()
(8) * (-bx + ax)^3
```
"""
# Assert p is not 0 and that its non-zero coeffients are coprime.
# (We could just work with the primitive part p/p.content() but we want to be
# aware if factor() does not return a primitive part in future sage versions.)
assert p.content() == 1
# Ensure that the first non-zero coefficient is positive.
return p if p.lc() > 0 else -p
def conflicts(R, con):
"""Check whether any of the passed non-zero assumptions is implied by the zero assumptions"""
zero = R.ideal(list(map(numerator, con.zero)))
if 1 in zero:
return True
# First a cheap check whether any of the individual nonzero terms conflict on
# their own.
for nonzero in con.nonzero:
if nonzero.iszero(zero):
return True
# It can be the case that entries in the nonzero set do not individually
# conflict with the zero set, but their combination does. For example, knowing
# that either x or y is zero is equivalent to having x*y in the zero set.
# Having x or y individually in the nonzero set is not a conflict, but both
# simultaneously is, so that is the right thing to check for.
if reduce(lambda a,b: a * b, con.nonzero, fastfrac(R, 1)).iszero(zero):
return True
return False
def get_nonzero_set(R, assume):
"""Calculate a simple set of nonzero expressions"""
zero = R.ideal(list(map(numerator, assume.zero)))
nonzero = set()
for nz in map(numerator, assume.nonzero):
for (f,n) in nz.factor():
nonzero.add(normalize_factor(f))
rnz = zero.reduce(nz)
for (f,n) in rnz.factor():
nonzero.add(normalize_factor(f))
return nonzero
def prove_nonzero(R, exprs, assume):
"""Check whether an expression is provably nonzero, given assumptions"""
zero = R.ideal(list(map(numerator, assume.zero)))
nonzero = get_nonzero_set(R, assume)
expl = set()
ok = True
for expr in exprs:
if numerator(expr) in zero:
return (False, [exprs[expr]])
allexprs = reduce(lambda a,b: numerator(a)*numerator(b), exprs, 1)
for (f, n) in allexprs.factor():
if normalize_factor(f) not in nonzero:
ok = False
if ok:
return (True, None)
ok = True
for (f, n) in zero.reduce(allexprs).factor():
if normalize_factor(f) not in nonzero:
ok = False
if ok:
return (True, None)
ok = True
for expr in exprs:
for (f,n) in numerator(expr).factor():
if normalize_factor(f) not in nonzero:
ok = False
if ok:
return (True, None)
ok = True
for expr in exprs:
for (f,n) in zero.reduce(numerator(expr)).factor():
if normalize_factor(f) not in nonzero:
expl.add(exprs[expr])
if expl:
return (False, list(expl))
else:
return (True, None)
def prove_zero(R, exprs, assume):
"""Check whether all of the passed expressions are provably zero, given assumptions"""
r, e = prove_nonzero(R, dict(map(lambda x: (fastfrac(R, x.bot, 1), exprs[x]), exprs)), assume)
if not r:
return (False, list(map(lambda x: "Possibly zero denominator: %s" % x, e)))
zero = R.ideal(list(map(numerator, assume.zero)))
nonzero = prod(x for x in assume.nonzero)
expl = []
for expr in exprs:
if not expr.iszero(zero):
expl.append(exprs[expr])
if not expl:
return (True, None)
return (False, expl)
def describe_extra(R, assume, assumeExtra):
"""Describe what assumptions are added, given existing assumptions"""
zerox = assume.zero.copy()
zerox.update(assumeExtra.zero)
zero = R.ideal(list(map(numerator, assume.zero)))
zeroextra = R.ideal(list(map(numerator, zerox)))
nonzero = get_nonzero_set(R, assume)
ret = set()
# Iterate over the extra zero expressions
for base in assumeExtra.zero:
if base not in zero:
add = []
for (f, n) in numerator(base).factor():
if normalize_factor(f) not in nonzero:
add += ["%s" % normalize_factor(f)]
if add:
ret.add((" * ".join(add)) + " = 0 [%s]" % assumeExtra.zero[base])
# Iterate over the extra nonzero expressions
for nz in assumeExtra.nonzero:
nzr = zeroextra.reduce(numerator(nz))
if nzr not in zeroextra:
for (f,n) in nzr.factor():
if normalize_factor(zeroextra.reduce(f)) not in nonzero:
ret.add("%s != 0" % normalize_factor(zeroextra.reduce(f)))
return ", ".join(x for x in ret)
def check_symbolic(R, assumeLaw, assumeAssert, assumeBranch, require):
"""Check a set of zero and nonzero requirements, given a set of zero and nonzero assumptions"""
assume = assumeLaw + assumeAssert + assumeBranch
if conflicts(R, assume):
# This formula does not apply
return (True, None)
describe = describe_extra(R, assumeLaw + assumeBranch, assumeAssert)
if describe != "":
describe = " (assuming " + describe + ")"
ok, msg = prove_zero(R, require.zero, assume)
if not ok:
return (False, "FAIL, %s fails%s" % (str(msg), describe))
res, expl = prove_nonzero(R, require.nonzero, assume)
if not res:
return (False, "FAIL, %s fails%s" % (str(expl), describe))
return (True, "OK%s" % describe)
def concrete_verify(c):
for k in c.zero:
if k != 0:
return (False, c.zero[k])
for k in c.nonzero:
if k == 0:
return (False, c.nonzero[k])
return (True, None)

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# Test libsecp256k1' group operation implementations using prover.sage
import sys
load("group_prover.sage")
load("weierstrass_prover.sage")
def formula_secp256k1_gej_double_var(a):
"""libsecp256k1's secp256k1_gej_double_var, used by various addition functions"""
rz = a.Z * a.Y
s = a.Y^2
l = a.X^2
l = l * 3
l = l / 2
t = -s
t = t * a.X
rx = l^2
rx = rx + t
rx = rx + t
s = s^2
t = t + rx
ry = t * l
ry = ry + s
ry = -ry
return jacobianpoint(rx, ry, rz)
def formula_secp256k1_gej_add_var(branch, a, b):
"""libsecp256k1's secp256k1_gej_add_var"""
if branch == 0:
return (constraints(), constraints(nonzero={a.Infinity : 'a_infinite'}), b)
if branch == 1:
return (constraints(), constraints(zero={a.Infinity : 'a_finite'}, nonzero={b.Infinity : 'b_infinite'}), a)
z22 = b.Z^2
z12 = a.Z^2
u1 = a.X * z22
u2 = b.X * z12
s1 = a.Y * z22
s1 = s1 * b.Z
s2 = b.Y * z12
s2 = s2 * a.Z
h = -u1
h = h + u2
i = -s2
i = i + s1
if branch == 2:
r = formula_secp256k1_gej_double_var(a)
return (constraints(), constraints(zero={h : 'h=0', i : 'i=0', a.Infinity : 'a_finite', b.Infinity : 'b_finite'}), r)
if branch == 3:
return (constraints(), constraints(zero={h : 'h=0', a.Infinity : 'a_finite', b.Infinity : 'b_finite'}, nonzero={i : 'i!=0'}), point_at_infinity())
t = h * b.Z
rz = a.Z * t
h2 = h^2
h2 = -h2
h3 = h2 * h
t = u1 * h2
rx = i^2
rx = rx + h3
rx = rx + t
rx = rx + t
t = t + rx
ry = t * i
h3 = h3 * s1
ry = ry + h3
return (constraints(), constraints(zero={a.Infinity : 'a_finite', b.Infinity : 'b_finite'}, nonzero={h : 'h!=0'}), jacobianpoint(rx, ry, rz))
def formula_secp256k1_gej_add_ge_var(branch, a, b):
"""libsecp256k1's secp256k1_gej_add_ge_var, which assume bz==1"""
if branch == 0:
return (constraints(zero={b.Z - 1 : 'b.z=1'}), constraints(nonzero={a.Infinity : 'a_infinite'}), b)
if branch == 1:
return (constraints(zero={b.Z - 1 : 'b.z=1'}), constraints(zero={a.Infinity : 'a_finite'}, nonzero={b.Infinity : 'b_infinite'}), a)
z12 = a.Z^2
u1 = a.X
u2 = b.X * z12
s1 = a.Y
s2 = b.Y * z12
s2 = s2 * a.Z
h = -u1
h = h + u2
i = -s2
i = i + s1
if (branch == 2):
r = formula_secp256k1_gej_double_var(a)
return (constraints(zero={b.Z - 1 : 'b.z=1'}), constraints(zero={a.Infinity : 'a_finite', b.Infinity : 'b_finite', h : 'h=0', i : 'i=0'}), r)
if (branch == 3):
return (constraints(zero={b.Z - 1 : 'b.z=1'}), constraints(zero={a.Infinity : 'a_finite', b.Infinity : 'b_finite', h : 'h=0'}, nonzero={i : 'i!=0'}), point_at_infinity())
rz = a.Z * h
h2 = h^2
h2 = -h2
h3 = h2 * h
t = u1 * h2
rx = i^2
rx = rx + h3
rx = rx + t
rx = rx + t
t = t + rx
ry = t * i
h3 = h3 * s1
ry = ry + h3
return (constraints(zero={b.Z - 1 : 'b.z=1'}), constraints(zero={a.Infinity : 'a_finite', b.Infinity : 'b_finite'}, nonzero={h : 'h!=0'}), jacobianpoint(rx, ry, rz))
def formula_secp256k1_gej_add_zinv_var(branch, a, b):
"""libsecp256k1's secp256k1_gej_add_zinv_var"""
bzinv = b.Z^(-1)
if branch == 0:
rinf = b.Infinity
bzinv2 = bzinv^2
bzinv3 = bzinv2 * bzinv
rx = b.X * bzinv2
ry = b.Y * bzinv3
rz = 1
return (constraints(), constraints(nonzero={a.Infinity : 'a_infinite'}), jacobianpoint(rx, ry, rz, rinf))
if branch == 1:
return (constraints(), constraints(zero={a.Infinity : 'a_finite'}, nonzero={b.Infinity : 'b_infinite'}), a)
azz = a.Z * bzinv
z12 = azz^2
u1 = a.X
u2 = b.X * z12
s1 = a.Y
s2 = b.Y * z12
s2 = s2 * azz
h = -u1
h = h + u2
i = -s2
i = i + s1
if branch == 2:
r = formula_secp256k1_gej_double_var(a)
return (constraints(), constraints(zero={a.Infinity : 'a_finite', b.Infinity : 'b_finite', h : 'h=0', i : 'i=0'}), r)
if branch == 3:
return (constraints(), constraints(zero={a.Infinity : 'a_finite', b.Infinity : 'b_finite', h : 'h=0'}, nonzero={i : 'i!=0'}), point_at_infinity())
rz = a.Z * h
h2 = h^2
h2 = -h2
h3 = h2 * h
t = u1 * h2
rx = i^2
rx = rx + h3
rx = rx + t
rx = rx + t
t = t + rx
ry = t * i
h3 = h3 * s1
ry = ry + h3
return (constraints(), constraints(zero={a.Infinity : 'a_finite', b.Infinity : 'b_finite'}, nonzero={h : 'h!=0'}), jacobianpoint(rx, ry, rz))
def formula_secp256k1_gej_add_ge(branch, a, b):
"""libsecp256k1's secp256k1_gej_add_ge"""
zeroes = {}
nonzeroes = {}
a_infinity = False
if (branch & 2) != 0:
nonzeroes.update({a.Infinity : 'a_infinite'})
a_infinity = True
else:
zeroes.update({a.Infinity : 'a_finite'})
zz = a.Z^2
u1 = a.X
u2 = b.X * zz
s1 = a.Y
s2 = b.Y * zz
s2 = s2 * a.Z
t = u1
t = t + u2
m = s1
m = m + s2
rr = t^2
m_alt = -u2
tt = u1 * m_alt
rr = rr + tt
degenerate = (branch & 1) != 0
if degenerate:
zeroes.update({m : 'm_zero'})
else:
nonzeroes.update({m : 'm_nonzero'})
rr_alt = s1
rr_alt = rr_alt * 2
m_alt = m_alt + u1
if not degenerate:
rr_alt = rr
m_alt = m
n = m_alt^2
q = -t
q = q * n
n = n^2
if degenerate:
n = m
t = rr_alt^2
rz = a.Z * m_alt
t = t + q
rx = t
t = t * 2
t = t + q
t = t * rr_alt
t = t + n
ry = -t
ry = ry / 2
if a_infinity:
rx = b.X
ry = b.Y
rz = 1
if (branch & 4) != 0:
zeroes.update({rz : 'r.z = 0'})
return (constraints(zero={b.Z - 1 : 'b.z=1', b.Infinity : 'b_finite'}), constraints(zero=zeroes, nonzero=nonzeroes), point_at_infinity())
else:
nonzeroes.update({rz : 'r.z != 0'})
return (constraints(zero={b.Z - 1 : 'b.z=1', b.Infinity : 'b_finite'}), constraints(zero=zeroes, nonzero=nonzeroes), jacobianpoint(rx, ry, rz))
def formula_secp256k1_gej_add_ge_old(branch, a, b):
"""libsecp256k1's old secp256k1_gej_add_ge, which fails when ay+by=0 but ax!=bx"""
a_infinity = (branch & 1) != 0
zero = {}
nonzero = {}
if a_infinity:
nonzero.update({a.Infinity : 'a_infinite'})
else:
zero.update({a.Infinity : 'a_finite'})
zz = a.Z^2
u1 = a.X
u2 = b.X * zz
s1 = a.Y
s2 = b.Y * zz
s2 = s2 * a.Z
z = a.Z
t = u1
t = t + u2
m = s1
m = m + s2
n = m^2
q = n * t
n = n^2
rr = t^2
t = u1 * u2
t = -t
rr = rr + t
t = rr^2
rz = m * z
infinity = False
if (branch & 2) != 0:
if not a_infinity:
infinity = True
else:
return (constraints(zero={b.Z - 1 : 'b.z=1', b.Infinity : 'b_finite'}), constraints(nonzero={z : 'conflict_a'}, zero={z : 'conflict_b'}), point_at_infinity())
zero.update({rz : 'r.z=0'})
else:
nonzero.update({rz : 'r.z!=0'})
rz = rz * (0 if a_infinity else 2)
rx = t
q = -q
rx = rx + q
q = q * 3
t = t * 2
t = t + q
t = t * rr
t = t + n
ry = -t
rx = rx * (0 if a_infinity else 4)
ry = ry * (0 if a_infinity else 4)
t = b.X
t = t * (1 if a_infinity else 0)
rx = rx + t
t = b.Y
t = t * (1 if a_infinity else 0)
ry = ry + t
t = (1 if a_infinity else 0)
rz = rz + t
if infinity:
return (constraints(zero={b.Z - 1 : 'b.z=1', b.Infinity : 'b_finite'}), constraints(zero=zero, nonzero=nonzero), point_at_infinity())
return (constraints(zero={b.Z - 1 : 'b.z=1', b.Infinity : 'b_finite'}), constraints(zero=zero, nonzero=nonzero), jacobianpoint(rx, ry, rz))
if __name__ == "__main__":
success = True
success = success & check_symbolic_jacobian_weierstrass("secp256k1_gej_add_var", 0, 7, 5, formula_secp256k1_gej_add_var)
success = success & check_symbolic_jacobian_weierstrass("secp256k1_gej_add_ge_var", 0, 7, 5, formula_secp256k1_gej_add_ge_var)
success = success & check_symbolic_jacobian_weierstrass("secp256k1_gej_add_zinv_var", 0, 7, 5, formula_secp256k1_gej_add_zinv_var)
success = success & check_symbolic_jacobian_weierstrass("secp256k1_gej_add_ge", 0, 7, 8, formula_secp256k1_gej_add_ge)
success = success & (not check_symbolic_jacobian_weierstrass("secp256k1_gej_add_ge_old [should fail]", 0, 7, 4, formula_secp256k1_gej_add_ge_old))
if len(sys.argv) >= 2 and sys.argv[1] == "--exhaustive":
success = success & check_exhaustive_jacobian_weierstrass("secp256k1_gej_add_var", 0, 7, 5, formula_secp256k1_gej_add_var, 43)
success = success & check_exhaustive_jacobian_weierstrass("secp256k1_gej_add_ge_var", 0, 7, 5, formula_secp256k1_gej_add_ge_var, 43)
success = success & check_exhaustive_jacobian_weierstrass("secp256k1_gej_add_zinv_var", 0, 7, 5, formula_secp256k1_gej_add_zinv_var, 43)
success = success & check_exhaustive_jacobian_weierstrass("secp256k1_gej_add_ge", 0, 7, 8, formula_secp256k1_gej_add_ge, 43)
success = success & (not check_exhaustive_jacobian_weierstrass("secp256k1_gej_add_ge_old [should fail]", 0, 7, 4, formula_secp256k1_gej_add_ge_old, 43))
sys.exit(int(not success))

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@@ -0,0 +1,39 @@
"""Prime order of finite field underlying secp256k1 (2^256 - 2^32 - 977)"""
P = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFC2F
"""Finite field underlying secp256k1"""
F = FiniteField(P)
"""Elliptic curve secp256k1: y^2 = x^3 + 7"""
C = EllipticCurve([F(0), F(7)])
"""Base point of secp256k1"""
G = C.lift_x(0x79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798)
if int(G[1]) & 1:
# G.y is even
G = -G
"""Prime order of secp256k1"""
N = C.order()
"""Finite field of scalars of secp256k1"""
Z = FiniteField(N)
""" Beta value of secp256k1 non-trivial endomorphism: lambda * (x, y) = (beta * x, y)"""
BETA = F(2)^((P-1)/3)
""" Lambda value of secp256k1 non-trivial endomorphism: lambda * (x, y) = (beta * x, y)"""
LAMBDA = Z(3)^((N-1)/3)
assert is_prime(P)
assert is_prime(N)
assert BETA != F(1)
assert BETA^3 == F(1)
assert BETA^2 + BETA + 1 == 0
assert LAMBDA != Z(1)
assert LAMBDA^3 == Z(1)
assert LAMBDA^2 + LAMBDA + 1 == 0
assert Integer(LAMBDA)*G == C(BETA*G[0], G[1])

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@@ -0,0 +1,275 @@
# Prover implementation for Weierstrass curves of the form
# y^2 = x^3 + A * x + B, specifically with a = 0 and b = 7, with group laws
# operating on affine and Jacobian coordinates, including the point at infinity
# represented by a 4th variable in coordinates.
load("group_prover.sage")
class affinepoint:
def __init__(self, x, y, infinity=0):
self.x = x
self.y = y
self.infinity = infinity
def __str__(self):
return "affinepoint(x=%s,y=%s,inf=%s)" % (self.x, self.y, self.infinity)
class jacobianpoint:
def __init__(self, x, y, z, infinity=0):
self.X = x
self.Y = y
self.Z = z
self.Infinity = infinity
def __str__(self):
return "jacobianpoint(X=%s,Y=%s,Z=%s,inf=%s)" % (self.X, self.Y, self.Z, self.Infinity)
def point_at_infinity():
return jacobianpoint(1, 1, 1, 1)
def negate(p):
if p.__class__ == affinepoint:
return affinepoint(p.x, -p.y)
if p.__class__ == jacobianpoint:
return jacobianpoint(p.X, -p.Y, p.Z)
assert(False)
def on_weierstrass_curve(A, B, p):
"""Return a set of zero-expressions for an affine point to be on the curve"""
return constraints(zero={p.x^3 + A*p.x + B - p.y^2: 'on_curve'})
def tangential_to_weierstrass_curve(A, B, p12, p3):
"""Return a set of zero-expressions for ((x12,y12),(x3,y3)) to be a line that is tangential to the curve at (x12,y12)"""
return constraints(zero={
(p12.y - p3.y) * (p12.y * 2) - (p12.x^2 * 3 + A) * (p12.x - p3.x): 'tangential_to_curve'
})
def colinear(p1, p2, p3):
"""Return a set of zero-expressions for ((x1,y1),(x2,y2),(x3,y3)) to be collinear"""
return constraints(zero={
(p1.y - p2.y) * (p1.x - p3.x) - (p1.y - p3.y) * (p1.x - p2.x): 'colinear_1',
(p2.y - p3.y) * (p2.x - p1.x) - (p2.y - p1.y) * (p2.x - p3.x): 'colinear_2',
(p3.y - p1.y) * (p3.x - p2.x) - (p3.y - p2.y) * (p3.x - p1.x): 'colinear_3'
})
def good_affine_point(p):
return constraints(nonzero={p.x : 'nonzero_x', p.y : 'nonzero_y'})
def good_jacobian_point(p):
return constraints(nonzero={p.X : 'nonzero_X', p.Y : 'nonzero_Y', p.Z^6 : 'nonzero_Z'})
def good_point(p):
return constraints(nonzero={p.Z^6 : 'nonzero_X'})
def finite(p, *affine_fns):
con = good_point(p) + constraints(zero={p.Infinity : 'finite_point'})
if p.Z != 0:
return con + reduce(lambda a, b: a + b, (f(affinepoint(p.X / p.Z^2, p.Y / p.Z^3)) for f in affine_fns), con)
else:
return con
def infinite(p):
return constraints(nonzero={p.Infinity : 'infinite_point'})
def law_jacobian_weierstrass_add(A, B, pa, pb, pA, pB, pC):
"""Check whether the passed set of coordinates is a valid Jacobian add, given assumptions"""
assumeLaw = (good_affine_point(pa) +
good_affine_point(pb) +
good_jacobian_point(pA) +
good_jacobian_point(pB) +
on_weierstrass_curve(A, B, pa) +
on_weierstrass_curve(A, B, pb) +
finite(pA) +
finite(pB) +
constraints(nonzero={pa.x - pb.x : 'different_x'}))
require = (finite(pC, lambda pc: on_weierstrass_curve(A, B, pc) +
colinear(pa, pb, negate(pc))))
return (assumeLaw, require)
def law_jacobian_weierstrass_double(A, B, pa, pb, pA, pB, pC):
"""Check whether the passed set of coordinates is a valid Jacobian doubling, given assumptions"""
assumeLaw = (good_affine_point(pa) +
good_affine_point(pb) +
good_jacobian_point(pA) +
good_jacobian_point(pB) +
on_weierstrass_curve(A, B, pa) +
on_weierstrass_curve(A, B, pb) +
finite(pA) +
finite(pB) +
constraints(zero={pa.x - pb.x : 'equal_x', pa.y - pb.y : 'equal_y'}))
require = (finite(pC, lambda pc: on_weierstrass_curve(A, B, pc) +
tangential_to_weierstrass_curve(A, B, pa, negate(pc))))
return (assumeLaw, require)
def law_jacobian_weierstrass_add_opposites(A, B, pa, pb, pA, pB, pC):
assumeLaw = (good_affine_point(pa) +
good_affine_point(pb) +
good_jacobian_point(pA) +
good_jacobian_point(pB) +
on_weierstrass_curve(A, B, pa) +
on_weierstrass_curve(A, B, pb) +
finite(pA) +
finite(pB) +
constraints(zero={pa.x - pb.x : 'equal_x', pa.y + pb.y : 'opposite_y'}))
require = infinite(pC)
return (assumeLaw, require)
def law_jacobian_weierstrass_add_infinite_a(A, B, pa, pb, pA, pB, pC):
assumeLaw = (good_affine_point(pa) +
good_affine_point(pb) +
good_jacobian_point(pA) +
good_jacobian_point(pB) +
on_weierstrass_curve(A, B, pb) +
infinite(pA) +
finite(pB))
require = finite(pC, lambda pc: constraints(zero={pc.x - pb.x : 'c.x=b.x', pc.y - pb.y : 'c.y=b.y'}))
return (assumeLaw, require)
def law_jacobian_weierstrass_add_infinite_b(A, B, pa, pb, pA, pB, pC):
assumeLaw = (good_affine_point(pa) +
good_affine_point(pb) +
good_jacobian_point(pA) +
good_jacobian_point(pB) +
on_weierstrass_curve(A, B, pa) +
infinite(pB) +
finite(pA))
require = finite(pC, lambda pc: constraints(zero={pc.x - pa.x : 'c.x=a.x', pc.y - pa.y : 'c.y=a.y'}))
return (assumeLaw, require)
def law_jacobian_weierstrass_add_infinite_ab(A, B, pa, pb, pA, pB, pC):
assumeLaw = (good_affine_point(pa) +
good_affine_point(pb) +
good_jacobian_point(pA) +
good_jacobian_point(pB) +
infinite(pA) +
infinite(pB))
require = infinite(pC)
return (assumeLaw, require)
laws_jacobian_weierstrass = {
'add': law_jacobian_weierstrass_add,
'double': law_jacobian_weierstrass_double,
'add_opposite': law_jacobian_weierstrass_add_opposites,
'add_infinite_a': law_jacobian_weierstrass_add_infinite_a,
'add_infinite_b': law_jacobian_weierstrass_add_infinite_b,
'add_infinite_ab': law_jacobian_weierstrass_add_infinite_ab
}
def check_exhaustive_jacobian_weierstrass(name, A, B, branches, formula, p):
"""Verify an implementation of addition of Jacobian points on a Weierstrass curve, by executing and validating the result for every possible addition in a prime field"""
F = Integers(p)
print("Formula %s on Z%i:" % (name, p))
points = []
for x in range(0, p):
for y in range(0, p):
point = affinepoint(F(x), F(y))
r, e = concrete_verify(on_weierstrass_curve(A, B, point))
if r:
points.append(point)
ret = True
for za in range(1, p):
for zb in range(1, p):
for pa in points:
for pb in points:
for ia in range(2):
for ib in range(2):
pA = jacobianpoint(pa.x * F(za)^2, pa.y * F(za)^3, F(za), ia)
pB = jacobianpoint(pb.x * F(zb)^2, pb.y * F(zb)^3, F(zb), ib)
for branch in range(0, branches):
assumeAssert, assumeBranch, pC = formula(branch, pA, pB)
pC.X = F(pC.X)
pC.Y = F(pC.Y)
pC.Z = F(pC.Z)
pC.Infinity = F(pC.Infinity)
r, e = concrete_verify(assumeAssert + assumeBranch)
if r:
match = False
for key in laws_jacobian_weierstrass:
assumeLaw, require = laws_jacobian_weierstrass[key](A, B, pa, pb, pA, pB, pC)
r, e = concrete_verify(assumeLaw)
if r:
if match:
print(" multiple branches for (%s,%s,%s,%s) + (%s,%s,%s,%s)" % (pA.X, pA.Y, pA.Z, pA.Infinity, pB.X, pB.Y, pB.Z, pB.Infinity))
else:
match = True
r, e = concrete_verify(require)
if not r:
ret = False
print(" failure in branch %i for (%s,%s,%s,%s) + (%s,%s,%s,%s) = (%s,%s,%s,%s): %s" % (branch, pA.X, pA.Y, pA.Z, pA.Infinity, pB.X, pB.Y, pB.Z, pB.Infinity, pC.X, pC.Y, pC.Z, pC.Infinity, e))
print()
return ret
def check_symbolic_function(R, assumeAssert, assumeBranch, f, A, B, pa, pb, pA, pB, pC):
assumeLaw, require = f(A, B, pa, pb, pA, pB, pC)
return check_symbolic(R, assumeLaw, assumeAssert, assumeBranch, require)
def check_symbolic_jacobian_weierstrass(name, A, B, branches, formula):
"""Verify an implementation of addition of Jacobian points on a Weierstrass curve symbolically"""
R.<ax,bx,ay,by,Az,Bz,Ai,Bi> = PolynomialRing(QQ,8,order='invlex')
lift = lambda x: fastfrac(R,x)
ax = lift(ax)
ay = lift(ay)
Az = lift(Az)
bx = lift(bx)
by = lift(by)
Bz = lift(Bz)
Ai = lift(Ai)
Bi = lift(Bi)
pa = affinepoint(ax, ay, Ai)
pb = affinepoint(bx, by, Bi)
pA = jacobianpoint(ax * Az^2, ay * Az^3, Az, Ai)
pB = jacobianpoint(bx * Bz^2, by * Bz^3, Bz, Bi)
res = {}
for key in laws_jacobian_weierstrass:
res[key] = []
print("Formula " + name + ":")
count = 0
ret = True
for branch in range(branches):
assumeFormula, assumeBranch, pC = formula(branch, pA, pB)
assumeBranch = assumeBranch.map(lift)
assumeFormula = assumeFormula.map(lift)
pC.X = lift(pC.X)
pC.Y = lift(pC.Y)
pC.Z = lift(pC.Z)
pC.Infinity = lift(pC.Infinity)
for key in laws_jacobian_weierstrass:
success, msg = check_symbolic_function(R, assumeFormula, assumeBranch, laws_jacobian_weierstrass[key], A, B, pa, pb, pA, pB, pC)
if not success:
ret = False
res[key].append((msg, branch))
for key in res:
print(" %s:" % key)
val = res[key]
for x in val:
if x[0] is not None:
print(" branch %i: %s" % (x[1], x[0]))
print()
return ret