816 lines
26 KiB
Python
816 lines
26 KiB
Python
#!/usr/bin/sage
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# vim: syntax=python
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# vim: set ts=2 sw=2 et:
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# Constantine
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# Copyright (c) 2018-2019 Status Research & Development GmbH
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# Copyright (c) 2020-Present Mamy André-Ratsimbazafy
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# Licensed and distributed under either of
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# * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT).
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# * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
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# at your option. This file may not be copied, modified, or distributed except according to those terms.
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# ############################################################
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#
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# Frobenius constants
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#
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# ############################################################
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# Imports
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# ---------------------------------------------------------
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import os
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import inspect, textwrap
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import sage.schemes.elliptic_curves.isogeny_small_degree as isd
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# Working directory
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# ---------------------------------------------------------
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os.chdir(os.path.dirname(__file__))
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# Sage imports
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# ---------------------------------------------------------
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# Accelerate arithmetic by accepting probabilistic proofs
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from sage.structure.proof.all import arithmetic
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arithmetic(False)
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load('curves.sage')
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# Utilities
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# ---------------------------------------------------------
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def fp2_to_hex(a):
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v = vector(a)
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return '0x' + Integer(v[0]).hex() + ' + β * ' + '0x' + Integer(v[1]).hex()
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def field_to_nim(value, field, curve, prefix = "", comment_above = "", comment_right = ""):
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result = '# ' + comment_above + '\n' if comment_above else ''
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comment_right = ' # ' + comment_right if comment_right else ''
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if field == 'Fp2':
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v = vector(value)
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result += inspect.cleandoc(f"""
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{prefix}Fp2[{curve}].fromHex( {comment_right}
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"0x{Integer(v[0]).hex()}",
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"0x{Integer(v[1]).hex()}"
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)""")
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elif field == 'Fp':
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result += inspect.cleandoc(f"""
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{prefix}Fp[{curve}].fromHex( {comment_right}
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"0x{Integer(value).hex()}")
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""")
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else:
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raise NotImplementedError()
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return result
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def dump_poly(name, poly, field, curve):
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result = f'const {name}* = [\n'
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result += ' # Polynomial k₀ + k₁ x + k₂ x² + k₃ x³ + ... + kₙ xⁿ\n'
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result += ' # The polynomial is stored as an array of coefficients ordered from k₀ to kₙ\n'
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result += '\n'
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poly = list(poly)
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lastRow = len(poly) - 1
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for rowID, val in enumerate(reversed(poly)):
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(coef, power) = val
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result += textwrap.indent(
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field_to_nim(
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coef, field, curve,
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comment_above = str(power)
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),
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' ')
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result += ',\n' if rowID != lastRow else '\n'
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result += ']'
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return result
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ZZR = PolynomialRing(ZZ, name='XX')
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def sgn0(x):
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"""
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Returns 1 if x is 'negative' (little-endian sense), else 0.
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"""
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degree = x.parent().degree()
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if degree == 1:
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# not a field extension
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xi_values = (ZZ(x),)
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else:
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# field extension
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xi_values = ZZR(x) # extract vector repr of field element (faster than x._vector_())
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sign = 0
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zero = 1
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# compute the sign in constant time
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for i in range(0, degree):
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zz_xi = xi_values[i]
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# sign of this digit
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sign_i = zz_xi % 2
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zero_i = zz_xi == 0
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# update sign and zero
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sign = sign | (zero & sign_i)
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zero = zero & zero_i
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return sign
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# Generic Shallue-van de Woestijne map
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# ---------------------------------------------------------
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def find_z_svdw(F, A, B):
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"""
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https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-14#appendix-H.1
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Arguments:
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- F, a field object, e.g., F = GF(2^521 - 1)
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- A and B, the coefficients of the curve y^2 = x^3 + A * x + B
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"""
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g = lambda x: F(x)^3 + F(A) * F(x) + F(B)
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h = lambda Z: -(F(3) * Z^2 + F(4) * A) / (F(4) * g(Z))
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ctr = F.gen()
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while True:
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for Z_cand in (F(ctr), F(-ctr)):
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if g(Z_cand) == F(0):
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# Criterion 1: g(Z) != 0 in F.
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continue
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if h(Z_cand) == F(0):
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# Criterion 2: -(3 * Z^2 + 4 * A) / (4 * g(Z)) != 0 in F.
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continue
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if not h(Z_cand).is_square():
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# Criterion 3: -(3 * Z^2 + 4 * A) / (4 * g(Z)) is square in F.
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continue
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if g(Z_cand).is_square() or g(-Z_cand / F(2)).is_square():
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# Criterion 4: At least one of g(Z) and g(-Z / 2) is square in F.
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return Z_cand
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ctr += 1
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# Isogenies for Simplified Shallue-van de Woestijne-Ulas map
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# ---------------------------------------------------------
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def find_iso(E):
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"""
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Find an isogenous curve with j-invariant not in {0, 1728} so that
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Simplified Shallue-van de Woestijne method is directly applicable
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(i.e the Elliptic Curve coefficient y² = x³ + A*x + B have AB != 0)
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"""
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for p_test in primes(30):
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isos = [i for i in isd.isogenies_prime_degree(E, p_test)
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if i.codomain().j_invariant() not in (0, 1728) ]
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if len(isos) > 0:
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print(f'✔️✔️✔️ Found {len(isos)} isogenous curves of degree {p_test}')
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return isos[0].dual()
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print(f'⚠️⚠️⚠️ Found no isogenies for {E}')
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return None
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def find_z_sswu(F, A, B):
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"""
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https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-14#appendix-H.2
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Arguments:
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- F, a field object, e.g., F = GF(2^521 - 1)
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- A and B, the coefficients of the curve equation y² = x³ + A * x + B
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"""
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R.<xx> = F[] # Polynomial ring over F
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g = xx^3 + F(A) * xx + F(B) # y² = g(x) = x³ + A * x + B
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ctr = F.gen()
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while True:
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for Z_cand in (F(ctr), F(-ctr)):
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if Z_cand.is_square():
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# Criterion 1: Z is non-square in F.
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continue
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if Z_cand == F(-1):
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# Criterion 2: Z != -1 in F.
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continue
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if not (g - Z_cand).is_irreducible():
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# Criterion 3: g(x) - Z is irreducible over F.
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continue
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if g(B / (Z_cand * A)).is_square():
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# Criterion 4: g(B / (Z * A)) is square in F.
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return Z_cand
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ctr += 1
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def search_isogeny(curve_name, curve_config):
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p = curve_config[curve_name]['field']['modulus']
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Fp = GF(p)
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# Base constants - E1
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A = curve_config[curve_name]['curve']['a']
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B = curve_config[curve_name]['curve']['b']
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E1 = EllipticCurve(Fp, [A, B])
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# Base constants - E2
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embedding_degree = curve_config[curve_name]['tower']['embedding_degree']
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twist_degree = curve_config[curve_name]['tower']['twist_degree']
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twist = curve_config[curve_name]['tower']['twist']
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G2_field_degree = embedding_degree // twist_degree
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G2_field = f'Fp{G2_field_degree}' if G2_field_degree > 1 else 'Fp'
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if G2_field_degree == 2:
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non_residue_fp = curve_config[curve_name]['tower']['QNR_Fp']
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elif G2_field_degree == 1:
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if twist_degree == 6:
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# Only for complete serialization
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non_residue_fp = curve_config[curve_name]['tower']['SNR_Fp']
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else:
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raise NotImplementedError()
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else:
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raise NotImplementedError()
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Fp = GF(p)
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K.<u> = PolynomialRing(Fp)
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if G2_field == 'Fp2':
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Fp2.<beta> = Fp.extension(u^2 - non_residue_fp)
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G2F = Fp2
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if twist_degree == 6:
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non_residue_twist = curve_config[curve_name]['tower']['SNR_Fp2']
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else:
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raise NotImplementedError()
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elif G2_field == 'Fp':
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G2F = Fp
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if twist_degree == 6:
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non_residue_twist = curve_config[curve_name]['tower']['SNR_Fp']
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else:
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raise NotImplementedError()
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else:
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raise NotImplementedError()
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if twist == 'D_Twist':
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G2B = B/G2F(non_residue_twist)
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E2 = EllipticCurve(G2F, [0, G2B])
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elif twist == 'M_Twist':
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G2B = B*G2F(non_residue_twist)
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E2 = EllipticCurve(G2F, [0, G2B])
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else:
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raise ValueError('E2 must be a D_Twist or M_Twist but found ' + twist)
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# Isogenies:
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iso_G1 = find_iso(E1)
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iso_G2 = find_iso(E2)
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if iso_G1 == None or iso_G2 == None:
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# TODO: case when G1 has a cheap isogeny but G2 does not
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Z_G1 = find_z_svdw(Fp, A, B)
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print(f"Z G1 (svdw): {Z_G1}")
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Z_G2 = find_z_svdw(Fp2, A, G2B)
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print(f"Z G2 (svdw): {fp2_to_hex(Z_G2)}")
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return
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a_G1 = iso_G1.domain().a4()
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b_G1 = iso_G1.domain().a6()
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a_G2 = iso_G2.domain().a4()
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b_G2 = iso_G2.domain().a6()
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# Z
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Z_G1 = find_z_sswu(Fp, a_G1, b_G1)
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Z_G2 = find_z_sswu(Fp2, a_G2, b_G2)
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print(f"{curve_name} G1 - isogeny of degree {iso_G1.degree()} with eq y² = x³ + A'x + B':")
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print(f" A': 0x{Integer(a_G1).hex()}")
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print(f" B': 0x{Integer(b_G1).hex()}")
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print(f" Z (sswu): {Z_G1}")
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print(f"{curve_name} G2 - isogeny of degree {iso_G2.degree()} with eq y² = x³ + A'x + B':")
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print(f" A': {fp2_to_hex(a_G2)}")
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print(f" B': {fp2_to_hex(b_G2)}")
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print(f" Z (sswu): {fp2_to_hex(Z_G2)}")
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# BLS12-381 G1
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# ---------------------------------------------------------
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# Hardcoding from spec:
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# - https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-11#section-8.8.1
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# - https://github.com/cfrg/draft-irtf-cfrg-hash-to-curve/blob/f7dd3761/poc/sswu_opt_3mod4.sage#L126-L132
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def genBLS12381G1_H2C_constants(curve_config):
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curve_name = 'BLS12_381'
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# ------------------------------------------
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p = curve_config[curve_name]['field']['modulus']
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Fp = GF(p)
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# ------------------------------------------
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# Hash to curve isogenous curve parameters
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# y² = x³ + A'*x + B'
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print('\n----> Hash-to-Curve map to isogenous BLS12-381 E\'1 <----\n')
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buf = inspect.cleandoc(f"""
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# Hash-to-Curve map to isogenous BLS12-381 E'1 constants
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# -----------------------------------------------------------------
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#
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# y² = x³ + A'*x + B' with p ≡ 3 (mod 4) the BLS12-381 characteristic (base modulus)
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#
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# Hardcoding from spec:
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# - https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-11#section-8.8.1
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# - https://github.com/cfrg/draft-irtf-cfrg-hash-to-curve/blob/f7dd3761/poc/sswu_opt_3mod4.sage#L126-L132
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""")
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buf += '\n\n'
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# Base constants
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Aprime_E1 = Fp('0x144698a3b8e9433d693a02c96d4982b0ea985383ee66a8d8e8981aefd881ac98936f8da0e0f97f5cf428082d584c1d')
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Bprime_E1 = Fp('0x12e2908d11688030018b12e8753eee3b2016c1f0f24f4070a0b9c14fcef35ef55a23215a316ceaa5d1cc48e98e172be0')
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Z = Fp(11)
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# Extra
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minus_A = -Aprime_E1
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ZmulA = Z * Aprime_E1
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sqrt_minus_Z3 = sqrt(-Z^3)
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buf += f'const {curve_name}_h2c_G1_Aprime_E1* = '
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buf += field_to_nim(Aprime_E1, 'Fp', curve_name)
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buf += '\n'
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buf += f'const {curve_name}_h2c_G1_Bprime_E1* = '
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buf += field_to_nim(Bprime_E1, 'Fp', curve_name)
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buf += '\n'
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buf += f'const {curve_name}_h2c_G1_Z* = '
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buf += field_to_nim(Z, 'Fp', curve_name)
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buf += '\n'
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buf += f'const {curve_name}_h2c_G1_minus_A* = '
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buf += field_to_nim(minus_A, 'Fp', curve_name)
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buf += '\n'
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buf += f'const {curve_name}_h2c_G1_ZmulA* = '
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buf += field_to_nim(ZmulA, 'Fp', curve_name)
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buf += '\n'
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buf += f'const {curve_name}_h2c_G1_sqrt_minus_Z3* = '
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buf += field_to_nim(sqrt_minus_Z3, 'Fp', curve_name)
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buf += '\n'
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return buf
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def genBLS12381G1_H2C_isogeny_map(curve_config):
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curve_name = 'BLS12_381'
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# Hash to curve isogenous curve parameters
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# y² = x³ + A'*x + B'
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print('\n----> Hash-to-Curve 3-isogeny map BLS12-381 E\'1 constants <----\n')
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buf = inspect.cleandoc(f"""
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# Hash-to-Curve 11-isogeny map BLS12-381 E'1 constants
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# -----------------------------------------------------------------
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#
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# The polynomials map a point (x', y') on the isogenous curve E'1
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# to (x, y) on E1, represented as (xnum/xden, y' * ynum/yden)
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""")
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buf += '\n\n'
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p = curve_config[curve_name]['field']['modulus']
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Fp = GF(p)
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# Base constants - E1
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A = curve_config[curve_name]['curve']['a']
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B = curve_config[curve_name]['curve']['b']
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E1 = EllipticCurve(Fp, [A, B])
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# Base constants - Isogenous curve E'1, degree 11
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Aprime_E1 = Fp('0x144698a3b8e9433d693a02c96d4982b0ea985383ee66a8d8e8981aefd881ac98936f8da0e0f97f5cf428082d584c1d')
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Bprime_E1 = Fp('0x12e2908d11688030018b12e8753eee3b2016c1f0f24f4070a0b9c14fcef35ef55a23215a316ceaa5d1cc48e98e172be0')
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Eprime1 = EllipticCurve(Fp, [Aprime_E1, Bprime_E1])
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iso = EllipticCurveIsogeny(E=E1, kernel=None, codomain=Eprime1, degree=11).dual()
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if (- iso.rational_maps()[1])(1, 1) > iso.rational_maps()[1](1, 1):
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iso.switch_sign()
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(xm, ym) = iso.rational_maps()
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maps = (xm.numerator(), xm.denominator(), ym.numerator(), ym.denominator())
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buf += dump_poly(
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'BLS12_381_h2c_G1_11_isogeny_map_xnum',
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xm.numerator(), 'Fp', curve_name)
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buf += '\n'
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buf += dump_poly(
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'BLS12_381_h2c_G1_11_isogeny_map_xden',
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xm.denominator(), 'Fp', curve_name)
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buf += '\n'
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buf += dump_poly(
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'BLS12_381_h2c_G1_11_isogeny_map_ynum',
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ym.numerator(), 'Fp', curve_name)
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buf += '\n'
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buf += dump_poly(
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'BLS12_381_h2c_G1_11_isogeny_map_yden',
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ym.denominator(), 'Fp', curve_name)
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return buf
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# BLS12-381 G2
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# ---------------------------------------------------------
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# Hardcoding from spec:
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# - https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-11#section-8.8.2
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# - https://github.com/cfrg/draft-irtf-cfrg-hash-to-curve/blob/f7dd3761/poc/sswu_opt_9mod16.sage#L142-L148
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def genBLS12381G2_H2C_constants(curve_config):
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curve_name = 'BLS12_381'
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# ------------------------------------------
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embdeg = curve_config[curve_name]['tower']['embedding_degree']
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twdeg = curve_config[curve_name]['tower']['twist_degree']
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g2field = f'Fp{embdeg//twdeg}' if (embdeg//twdeg) > 1 else 'Fp'
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p = curve_config[curve_name]['field']['modulus']
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Fp = GF(p)
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K.<u> = PolynomialRing(Fp)
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if g2field == 'Fp2':
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QNR_Fp = curve_config[curve_name]['tower']['QNR_Fp']
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Fp2.<beta> = Fp.extension(u^2 - QNR_Fp)
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else:
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SNR_Fp = curve_config[curve_name]['tower']['SNR_Fp']
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Fp2.<beta> = Fp.extension(u^2 - SNR_Fp)
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# ------------------------------------------
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# Hash to curve isogenous curve parameters
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# y² = x³ + A'*x + B'
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print('\n----> Hash-to-Curve map to isogenous BLS12-381 E\'2 <----\n')
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buf = inspect.cleandoc(f"""
|
||
# Hash-to-Curve map to isogenous BLS12-381 E'2 constants
|
||
# -----------------------------------------------------------------
|
||
#
|
||
# y² = x³ + A'*x + B' with p² = q ≡ 9 (mod 16), p the BLS12-381 characteristic (base modulus)
|
||
#
|
||
# Hardcoding from spec:
|
||
# - https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-11#section-8.8.2
|
||
# - https://github.com/cfrg/draft-irtf-cfrg-hash-to-curve/blob/f7dd3761/poc/sswu_opt_9mod16.sage#L142-L148
|
||
""")
|
||
buf += '\n\n'
|
||
|
||
# Base constants
|
||
Aprime_E2 = Fp2([0, 240])
|
||
Bprime_E2 = Fp2([1012, 1012])
|
||
Z = Fp2([-2, -1])
|
||
# Extra
|
||
minus_A = -Aprime_E2
|
||
ZmulA = Z * Aprime_E2
|
||
inv_Z3 = (Z^3)^-1 # modular inverse of Z³
|
||
(a, b) = vector(inv_Z3)
|
||
squared_norm_inv_Z3 = a^2 + b^2 # ||1/Z³||²
|
||
# x^((p-3)/4)) ≡ 1/√x (mod p) if p ≡ 3 (mod 4)
|
||
inv_norm_inv_Z3 = squared_norm_inv_Z3^((p-3)/4) # 1/||1/Z³||
|
||
|
||
buf += f'const {curve_name}_h2c_G2_Aprime_E2* = '
|
||
buf += field_to_nim(Aprime_E2, 'Fp2', curve_name, comment_right = "240𝑖")
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve_name}_h2c_G2_Bprime_E2* = '
|
||
buf += field_to_nim(Bprime_E2, 'Fp2', curve_name, comment_right = "1012 * (1 + 𝑖)")
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve_name}_h2c_G2_Z* = '
|
||
buf += field_to_nim(Z, 'Fp2', curve_name, comment_right = "-(2 + 𝑖)")
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve_name}_h2c_G2_minus_A* = '
|
||
buf += field_to_nim(minus_A, 'Fp2', curve_name, comment_right = "-240𝑖")
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve_name}_h2c_G2_ZmulA* = '
|
||
buf += field_to_nim(ZmulA, 'Fp2', curve_name, comment_right = "Z*A = 240-480𝑖")
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve_name}_h2c_G2_inv_Z3* = '
|
||
buf += field_to_nim(inv_Z3, 'Fp2', curve_name, comment_right = "1/Z³")
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve_name}_h2c_G2_squared_norm_inv_Z3* = '
|
||
buf += field_to_nim(squared_norm_inv_Z3, 'Fp', curve_name, comment_right = "||1/Z³||²")
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve_name}_h2c_G2_inv_norm_inv_Z3* = '
|
||
buf += field_to_nim(inv_norm_inv_Z3, 'Fp', curve_name, comment_right = "1/||1/Z³||")
|
||
buf += '\n'
|
||
|
||
return buf
|
||
|
||
def genBLS12381G2_H2C_isogeny_map(curve_config):
|
||
curve_name = 'BLS12_381'
|
||
|
||
# ------------------------------------------
|
||
p = curve_config[curve_name]['field']['modulus']
|
||
# This extension field construction
|
||
# does not work with isogenies :/
|
||
#
|
||
# embdeg = curve_config[curve_name]['tower']['embedding_degree']
|
||
# twdeg = curve_config[curve_name]['tower']['twist_degree']
|
||
# g2field = f'Fp{embdeg//twdeg}' if (embdeg//twdeg) > 1 else 'Fp'
|
||
#
|
||
# Fp = GF(p)
|
||
# K.<u> = PolynomialRing(Fp)
|
||
# if g2field == 'Fp2':
|
||
# QNR_Fp = curve_config[curve_name]['tower']['QNR_Fp']
|
||
# Fp2.<beta> = Fp.extension(u^2 - QNR_Fp)
|
||
# else:
|
||
# SNR_Fp = curve_config[curve_name]['tower']['SNR_Fp']
|
||
# Fp2.<beta> = Fp.extension(u^2 - SNR_Fp)
|
||
# ------------------------------------------
|
||
|
||
QNR_Fp = curve_config[curve_name]['tower']['QNR_Fp']
|
||
Fp2.<beta> = GF(p^2, modulus=(x^2-QNR_Fp))
|
||
|
||
# Hash to curve isogenous curve parameters
|
||
# y² = x³ + A'*x + B'
|
||
|
||
print('\n----> Hash-to-Curve 3-isogeny map BLS12-381 E\'2 constants <----\n')
|
||
buf = inspect.cleandoc(f"""
|
||
# Hash-to-Curve 3-isogeny map BLS12-381 E'2 constants
|
||
# -----------------------------------------------------------------
|
||
#
|
||
# The polynomials map a point (x', y') on the isogenous curve E'2
|
||
# to (x, y) on E2, represented as (xnum/xden, y' * ynum/yden)
|
||
|
||
""")
|
||
buf += '\n\n'
|
||
|
||
# Base constants - E2
|
||
A = curve_config[curve_name]['curve']['a']
|
||
B = curve_config[curve_name]['curve']['b']
|
||
twist = curve_config[curve_name]['tower']['twist']
|
||
SNR_Fp2 = curve_config[curve_name]['tower']['SNR_Fp2']
|
||
|
||
if twist == 'M_twist':
|
||
Btwist = B * Fp2(SNR_Fp2)
|
||
else:
|
||
Btwist = B / Fp2(SNR_Fp2)
|
||
|
||
E2 = EllipticCurve(Fp2, [A, Btwist])
|
||
|
||
# Base constants - Isogenous curve E'2, degree 3
|
||
Aprime_E2 = Fp2([0, 240])
|
||
Bprime_E2 = Fp2([1012, 1012])
|
||
Eprime2 = EllipticCurve(Fp2, [Aprime_E2, Bprime_E2])
|
||
|
||
iso_kernel = [6 * (1 - beta), 1]
|
||
iso = EllipticCurveIsogeny(E=Eprime2, kernel=iso_kernel, codomain=E2, degree=3)
|
||
if (- iso.rational_maps()[1])(1, 1) > iso.rational_maps()[1](1, 1):
|
||
iso.switch_sign()
|
||
|
||
(xm, ym) = iso.rational_maps()
|
||
maps = (xm.numerator(), xm.denominator(), ym.numerator(), ym.denominator())
|
||
|
||
buf += dump_poly(
|
||
'BLS12_381_h2c_G2_3_isogeny_map_xnum',
|
||
xm.numerator(), 'Fp2', curve_name)
|
||
buf += '\n'
|
||
buf += dump_poly(
|
||
'BLS12_381_h2c_G2_3_isogeny_map_xden',
|
||
xm.denominator(), 'Fp2', curve_name)
|
||
buf += '\n'
|
||
buf += dump_poly(
|
||
'BLS12_381_h2c_G2_3_isogeny_map_ynum',
|
||
ym.numerator(), 'Fp2', curve_name)
|
||
buf += '\n'
|
||
buf += dump_poly(
|
||
'BLS12_381_h2c_G2_3_isogeny_map_yden',
|
||
ym.denominator(), 'Fp2', curve_name)
|
||
|
||
return buf
|
||
|
||
def genSVDW_H2C_G1_constants(curve, curve_config, Z):
|
||
p = curve_config[curve]['field']['modulus']
|
||
a = curve_config[curve]['curve']['a']
|
||
b = curve_config[curve]['curve']['b']
|
||
|
||
Fp = GF(p)
|
||
|
||
print(f'\n----> Hash-to-Curve Shallue-van de Woestijne {curve} G1 map <----\n')
|
||
buf = inspect.cleandoc(f"""
|
||
# Hash-to-Curve Shallue-van de Woestijne {curve} G1 map
|
||
# -----------------------------------------------------------------
|
||
# Spec:
|
||
# - https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-14#appendix-F.1
|
||
""")
|
||
buf += '\n\n'
|
||
|
||
c1 = Z^3 + a*Z + b
|
||
c2 = -Z/2
|
||
t = 3 * Z^2 + 4 * a
|
||
c3 = sqrt(-c1 * t)
|
||
if sgn0(c3) == 1:
|
||
c3 = -c3
|
||
c4 = -4 * c1 / t
|
||
|
||
buf += f'const {curve}_h2c_svdw_G1_Z* = '
|
||
buf += field_to_nim(Z, 'Fp', curve)
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve}_h2c_svdw_G1_curve_eq_rhs_Z* = '
|
||
buf += field_to_nim(c1, 'Fp', curve)
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve}_h2c_svdw_G1_minus_Z_div_2* = '
|
||
buf += field_to_nim(c2, 'Fp', curve)
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve}_h2c_svdw_G1_z3* = '
|
||
buf += field_to_nim(c3, 'Fp', curve)
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve}_h2c_svdw_G1_z4* = '
|
||
buf += field_to_nim(c4, 'Fp', curve)
|
||
buf += '\n'
|
||
|
||
return buf
|
||
|
||
def genSVDW_H2C_G2_constants(curve, curve_config, Z):
|
||
p = curve_config[curve]['field']['modulus']
|
||
a = curve_config[curve]['curve']['a']
|
||
b = curve_config[curve]['curve']['b']
|
||
|
||
embedding_degree = curve_config[curve]['tower']['embedding_degree']
|
||
twist_degree = curve_config[curve]['tower']['twist_degree']
|
||
twist = curve_config[curve]['tower']['twist']
|
||
|
||
G2_field_degree = embedding_degree // twist_degree
|
||
G2_field = f'Fp{G2_field_degree}' if G2_field_degree > 1 else 'Fp'
|
||
|
||
if G2_field_degree == 2:
|
||
non_residue_fp = curve_config[curve]['tower']['QNR_Fp']
|
||
elif G2_field_degree == 1:
|
||
if twist_degree == 6:
|
||
# Only for complete serialization
|
||
non_residue_fp = curve_config[curve]['tower']['SNR_Fp']
|
||
else:
|
||
raise NotImplementedError()
|
||
else:
|
||
raise NotImplementedError()
|
||
|
||
Fp = GF(p)
|
||
K.<u> = PolynomialRing(Fp)
|
||
|
||
if G2_field == 'Fp2':
|
||
Fp2.<beta> = Fp.extension(u^2 - non_residue_fp)
|
||
G2F = Fp2
|
||
if twist_degree == 6:
|
||
non_residue_twist = curve_config[curve]['tower']['SNR_Fp2']
|
||
else:
|
||
raise NotImplementedError()
|
||
elif G2_field == 'Fp':
|
||
G2F = Fp
|
||
if twist_degree == 6:
|
||
non_residue_twist = curve_config[curve]['tower']['SNR_Fp']
|
||
else:
|
||
raise NotImplementedError()
|
||
else:
|
||
raise NotImplementedError()
|
||
|
||
if twist == 'D_Twist':
|
||
G2B = b/G2F(non_residue_twist)
|
||
elif twist == 'M_Twist':
|
||
G2B = b*G2F(non_residue_twist)
|
||
else:
|
||
raise ValueError('E2 must be a D_Twist or M_Twist but found ' + twist)
|
||
|
||
print(f'\n----> Hash-to-Curve Shallue-van de Woestijne {curve} G2 map <----\n')
|
||
buf = inspect.cleandoc(f"""
|
||
# Hash-to-Curve Shallue-van de Woestijne {curve} G2 map
|
||
# -----------------------------------------------------------------
|
||
# Spec:
|
||
# - https://datatracker.ietf.org/doc/html/draft-irtf-cfrg-hash-to-curve-14#appendix-F.1
|
||
""")
|
||
buf += '\n\n'
|
||
|
||
c1 = Z^3 + a*Z + G2B
|
||
c2 = -Z/2
|
||
t = 3 * Z^2 + 4 * a
|
||
c3 = sqrt(-c1 * t)
|
||
if sgn0(c3) == 1:
|
||
c3 = -c3
|
||
c4 = -4 * c1 / t
|
||
|
||
buf += f'const {curve}_h2c_svdw_G2_Z* = '
|
||
buf += field_to_nim(Z, G2_field, curve)
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve}_h2c_svdw_G2_curve_eq_rhs_Z* = '
|
||
buf += field_to_nim(c1, G2_field, curve)
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve}_h2c_svdw_G2_minus_Z_div_2* = '
|
||
buf += field_to_nim(c2, G2_field, curve)
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve}_h2c_svdw_G2_z3* = '
|
||
buf += field_to_nim(c3, G2_field, curve)
|
||
buf += '\n'
|
||
|
||
buf += f'const {curve}_h2c_svdw_G2_z4* = '
|
||
buf += field_to_nim(c4, G2_field, curve)
|
||
buf += '\n'
|
||
|
||
return buf
|
||
|
||
# CLI
|
||
# ---------------------------------------------------------
|
||
|
||
if __name__ == "__main__":
|
||
# Usage
|
||
# BLS12-381
|
||
# sage sage/derive_hash_to_curve.sage BLS12_381 G2
|
||
# for Hash-to-Curve
|
||
# or
|
||
# sage sage/derive_hash_to_curve.sage BLS12_381 iso
|
||
# to search for a suitable isogeny
|
||
|
||
from argparse import ArgumentParser
|
||
|
||
parser = ArgumentParser()
|
||
parser.add_argument("curve",nargs="+")
|
||
args = parser.parse_args()
|
||
|
||
curve = args.curve[0]
|
||
group_or_iso = args.curve[1]
|
||
|
||
if group_or_iso == 'iso':
|
||
search_isogeny(curve, Curves)
|
||
|
||
elif curve == 'BLS12_381' and group_or_iso == 'G1':
|
||
h2c = genBLS12381G1_H2C_constants(Curves)
|
||
h2c += '\n\n'
|
||
h2c += genBLS12381G1_H2C_isogeny_map(Curves)
|
||
|
||
with open(f'{curve.lower()}_hash_to_curve_g1.nim', 'w') as f:
|
||
f.write(copyright())
|
||
f.write('\n\n')
|
||
|
||
f.write(inspect.cleandoc("""
|
||
import
|
||
../config/curves,
|
||
../io/io_fields
|
||
"""))
|
||
|
||
f.write('\n\n')
|
||
f.write(h2c)
|
||
|
||
print(f'Successfully created {curve.lower()}_hash_to_curve_g1.nim')
|
||
|
||
elif curve == 'BLS12_381' and group_or_iso == 'G2':
|
||
h2c = genBLS12381G2_H2C_constants(Curves)
|
||
h2c += '\n\n'
|
||
h2c += genBLS12381G2_H2C_isogeny_map(Curves)
|
||
|
||
with open(f'{curve.lower()}_hash_to_curve_g2.nim', 'w') as f:
|
||
f.write(copyright())
|
||
f.write('\n\n')
|
||
|
||
f.write(inspect.cleandoc("""
|
||
import
|
||
../config/curves,
|
||
../io/[io_fields, io_extfields]
|
||
"""))
|
||
|
||
f.write('\n\n')
|
||
f.write(h2c)
|
||
|
||
print(f'Successfully created {curve.lower()}_hash_to_curve_g2.nim')
|
||
|
||
elif curve == 'BN254_Snarks' and group_or_iso == 'G1':
|
||
p = Curves['BN254_Snarks']['field']['modulus']
|
||
|
||
Z = GF(p)(1)
|
||
h2c = genSVDW_H2C_G1_constants('BN254_Snarks', Curves, Z)
|
||
|
||
with open(f'{curve.lower()}_hash_to_curve_g1.nim', 'w') as f:
|
||
f.write(copyright())
|
||
f.write('\n\n')
|
||
|
||
f.write(inspect.cleandoc("""
|
||
import
|
||
../config/curves,
|
||
../io/io_fields
|
||
"""))
|
||
|
||
f.write('\n\n')
|
||
f.write(h2c)
|
||
|
||
print(f'Successfully created {curve.lower()}_hash_to_curve_g1.nim')
|
||
|
||
elif curve == 'BN254_Snarks' and group_or_iso == 'G2':
|
||
p = Curves['BN254_Snarks']['field']['modulus']
|
||
non_residue_fp = Curves['BN254_Snarks']['tower']['QNR_Fp']
|
||
Fp = GF(p)
|
||
K.<u> = PolynomialRing(Fp)
|
||
Fp2.<beta> = Fp.extension(u^2 - non_residue_fp)
|
||
|
||
Z = Fp2([0, 1])
|
||
h2c = genSVDW_H2C_G2_constants('BN254_Snarks', Curves, Z)
|
||
|
||
with open(f'{curve.lower()}_hash_to_curve_g2.nim', 'w') as f:
|
||
f.write(copyright())
|
||
f.write('\n\n')
|
||
|
||
f.write(inspect.cleandoc("""
|
||
import
|
||
../config/curves,
|
||
../io/[io_fields, io_extfields]
|
||
"""))
|
||
|
||
f.write('\n\n')
|
||
f.write(h2c)
|
||
|
||
print(f'Successfully created {curve.lower()}_hash_to_curve_g2.nim')
|
||
else:
|
||
raise ValueError(
|
||
curve + group_or_iso +
|
||
' is not configured '
|
||
)
|