2024 CISCN Qual Writeup

import numpy as np
npz_file  = np.load("attachment.npz")

index = npz_file['index']
input = npz_file['input']
output = npz_file['output']
trace = npz_file['trace']
norms = {}
for i in range(520):
    if norms.get(index[i]) is None:
        norms[index[i]] = []
    norms[index[i]].append((np.linalg.norm(trace[i]),input[i]))

for key in norms:
    norm = sorted(norms[key],key=lambda x: x[0])[::-1]
    print(norm[0][1],end="")

a = 1000003
al = []
for i in range(8):
    al.append(a^i)


wl = []
for i in range(6):
    wl.append(al[i])

wl.append(2^7*al[7] + al[6])

m = matrix(ZZ,9,9)
x = 7457312583301101235
length = 7
mask = 0xffffffffffffffff
x = x ^^ length & mask
print(x)
wl.append(-x)
for i in range(8):
    m[i,0] = wl[i]*2**20
    m[i,i+1] = 1


m[-2,-1] = 2^ 8
m[-1,0] = 2^64*2**20


for v in m.LLL():
    cr = []
    if abs(v[-1]) == 256:
        c = v[1:-1] * sgn(v[-1])
        xx = x
        for ci in c:
            xx_ = (xx - ci)*inverse_mod(a,2**64)%2**64
            cr.append(xx^^(xx_*a)%2**64)
            xx = xx_
        print(cr)
        s = sum(a**i*c[i] for i in range(7)) + a ** 7 * 2 ** 7 * c[-1]
        s %= 2**64
        assert s == x
        break
msg = 13903983817893117249931704406959869971132956255130487015289848690577655239262013033618370827749581909492660806312017
key = bytes(ci for ci in cr[::-1])
import hashlib
print(bytes.fromhex(hex(msg^int(hashlib.sha384(binascii.hexlify(key)).hexdigest(), 16))[2:]))

import sympy
n = 111922722351752356094117957341697336848130397712588425954225300832977768690114834703654895285440684751636198779555891692340301590396539921700125219784729325979197290342352480495970455903120265334661588516182848933843212275742914269686197484648288073599387074325226321407600351615258973610780463417788580083967
e = 37059679294843322451875129178470872595128216054082068877693632035071251762179299783152435312052608685562859680569924924133175684413544051218945466380415013172416093939670064185752780945383069447693745538721548393982857225386614608359109463927663728739248286686902750649766277564516226052064304547032760477638585302695605907950461140971727150383104
c = 14999622534973796113769052025256345914577762432817016713135991450161695032250733213228587506601968633155119211807176051329626895125610484405486794783282214597165875393081405999090879096563311452831794796859427268724737377560053552626220191435015101496941337770496898383092414492348672126813183368337602023823
rr = e // n
kk = rr - 2
x = sympy.symbols('x')
f = (kk+rr) * x ** 2 + (rr * n + rr + 65537 + 1 - e) * x + rr * n
p_ = int(sympy.solve(f)[1])
P.<x> = PolynomialRing(Zmod(n))
f = x + p_
x0 = f.small_roots(X=2^75,beta=0.4)[0]
p = int(p_ + x0)
assert n % p == 0
q = n // int(p)
phi = (p-1)*(q-1)
e = 65537 + kk * p + rr * ((p+1) * (q+1)) + 1
d = pow(e,-1,phi)
m = pow(c,d,n)
print(bytes.fromhex(hex(m)[2:]))

def waff():
    def f():
        yield generator.gi_frame.f_back
    generator = f()
    frame = [x for x in generator][0]
    str = frame.f_back.f_back.f_back.f_globals['_'*2+"builtins"+'_'*2].str
    for i in str(frame.f_back.f_back.f_back.f_code.co_consts):
        print(i)
waff()