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author | Pieter Wuille <pieter@wuille.net> | 2020-10-14 11:41:15 -0700 |
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committer | Pieter Wuille <pieter@wuille.net> | 2020-10-14 11:41:15 -0700 |
commit | 9e5626d2a8ddbbd7640ff53f89f3a7021d747633 (patch) | |
tree | 95085289012230285b6cc1bb551ebf8a217121a0 /src/secp256k1/sage | |
parent | c2c4dbaebd955ad2829364f7fa5b8169ca1ba6b9 (diff) | |
parent | 52380bf304b1c02dda23f1e2fad0159e29b2f7a2 (diff) | |
download | bitcoin-9e5626d2a8ddbbd7640ff53f89f3a7021d747633.tar.xz |
Update libsecp256k1 subtree to latest master
Diffstat (limited to 'src/secp256k1/sage')
-rw-r--r-- | src/secp256k1/sage/gen_exhaustive_groups.sage | 129 |
1 files changed, 129 insertions, 0 deletions
diff --git a/src/secp256k1/sage/gen_exhaustive_groups.sage b/src/secp256k1/sage/gen_exhaustive_groups.sage new file mode 100644 index 0000000000..3c3c984811 --- /dev/null +++ b/src/secp256k1/sage/gen_exhaustive_groups.sage @@ -0,0 +1,129 @@ +# Define field size and field +P = 2^256 - 2^32 - 977 +F = GF(P) +BETA = F(0x7ae96a2b657c07106e64479eac3434e99cf0497512f58995c1396c28719501ee) + +assert(BETA != F(1) and BETA^3 == F(1)) + +orders_done = set() +results = {} +first = True +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") + continue + orders_done.add(n) + # Skip curves isomorphic to the real secp256k1 + if n.is_pseudoprime(): + print(" - Isomorphic to secp256k1") + continue + + print("- Finding subgroups") + + # Find what prime subgroups exist + for f, _ in n.factor(): + print("- Analyzing subgroup of order %i" % f) + # Skip subgroups of order >1000 + if f < 4 or f > 1000: + print(" - Bad size") + continue + + # Iterate over X coordinates until we find one that is on the curve, has order f, + # and for which curve isomorphism exists that maps it to X coordinate 1. + for x in range(1, P): + # Skip X coordinates not on the curve, and construct the full point otherwise. + if not E.is_x_coord(x): + continue + G = E.lift_x(F(x)) + + print(" - Analyzing (multiples of) point with X=%i" % x) + + # Skip points whose order is not a multiple of f. Project the point to have + # order f otherwise. + if (G.order() % f): + print(" - Bad order") + continue + G = G * (G.order() // f) + + # Find lambda for endomorphism. Skip if none can be found. + lam = None + for l in Integers(f)(1).nth_root(3, all=True): + if int(l)*G == E(BETA*G[0], G[1]): + lam = int(l) + break + if lam is None: + print(" - No endomorphism for this subgroup") + break + + # Now look for an isomorphism of the curve that gives this point an X + # coordinate equal to 1. + # If (x,y) is on y^2 = x^3 + b, then (a^2*x, a^3*y) is on y^2 = x^3 + a^6*b. + # So look for m=a^2=1/x. + m = F(1)/G[0] + if not m.is_square(): + print(" - No curve isomorphism maps it to a point with X=1") + continue + a = m.sqrt() + rb = a^6*b + RE = EllipticCurve(F, [0, rb]) + + # Use as generator twice the image of G under the above isormorphism. + # This means that generator*(1/2 mod f) will have X coordinate 1. + RG = RE(1, a^3*G[1]) * 2 + # And even Y coordinate. + if int(RG[1]) % 2: + RG = -RG + assert(RG.order() == f) + assert(lam*RG == RE(BETA*RG[0], RG[1])) + + # We have found curve RE:y^2=x^3+rb with generator RG of order f. Remember it + results[f] = {"b": rb, "G": RG, "lambda": lam} + print(" - Found solution") + break + + print("") + +print("") +print("") +print("/* To be put in src/group_impl.h: */") +first = True +for f in sorted(results.keys()): + b = results[f]["b"] + G = results[f]["G"] + print("# %s EXHAUSTIVE_TEST_ORDER == %i" % ("if" if first else "elif", f)) + first = False + print("static const secp256k1_ge secp256k1_ge_const_g = 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(");") + print("static const secp256k1_fe secp256k1_fe_const_b = SECP256K1_FE_CONST(") + print(" 0x%08x, 0x%08x, 0x%08x, 0x%08x," % tuple((int(b) >> (32 * (7 - i))) & 0xffffffff for i in range(4))) + print(" 0x%08x, 0x%08x, 0x%08x, 0x%08x" % tuple((int(b) >> (32 * (7 - i))) & 0xffffffff for i in range(4, 8))) + print(");") +print("# else") +print("# error No known generator for the specified exhaustive test group order.") +print("# endif") + +print("") +print("") +print("/* To be put in src/scalar_impl.h: */") +first = True +for f in sorted(results.keys()): + lam = results[f]["lambda"] + 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("") |