西湖论剑2021 Crypto unknown_dsa wp

最新推荐文章于 2023-02-06 21:39:43 发布

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最新推荐文章于 2023-02-06 21:39:43 发布 · 768 阅读

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#密码学

题目

from Crypto.Util.number import *
from Crypto.PublicKey import DSA
from Crypto.Hash import SHA
from gmpy2 import invert,powmod
import random
from secret import flag,m1,m2,ul,vl,wl

def encrypt():
    key = DSA.generate(int(1024))
    q = key.q
    p = key.p
    g = key.g
    x1 = bytes_to_long(flag[:len(flag)//2])
    x2 = bytes_to_long(flag[len(flag)//2:])
    assert x1<q and x2<q
    t = powmod(g, p*q-(p+q), p*q)
    hm1 = bytes_to_long(SHA.new(m1).digest())
    hm2 = bytes_to_long(SHA.new(m2).digest())
    k = random.randint(1, q-1)
    r1 = powmod(g, k, p) % q
    s1 = (hm1 + x1*r1) * invert(k, q) % q
    s2 = (hm2 + x1*r1) * invert(k, q) % q
    r2 = powmod(g, x1, p) % q
    s3 = (hm1 + x2*r2) * invert(k, q) % q
    print(p*q, (p-1)//q, t, sep=', ')
    print(r1, s1, s2, sep=', ')
    print(r2, s3, sep=', ')

def main():
    for i in range(len(ul)):
        assert ul[i]**2 - wl[i]* vl[i]**2==1
    e = 7
    cl1 <