Pwnhub Always be with U 学习

前言

前几天Pwnhub的一个密码学专题的比赛，当时我看了一会觉得没有想法不会做，就去忙别的事情了（我密码学是真的菜），现在各位师傅出writeup了，所以我就回来研究学习一下，结论：密码学的各种攻击知道的太少；密码学的库我用得不多，有的情况下不知道怎么编写代码。在文章里记录一下脚本，以后遇到了相似的题目也可以回来看看。

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题目一

参考链接：https://www.sjoerdlangkemper.nl/2016/08/23/compression-side-channel-attacks/

注意点：0x0a、缩小范围

from pwn import *

# context.log_level = 'debug'
p = remote("*.*.*.*", *)

result = "flag{"
result2 = "flag{"
while 1:
    for padding in xrange(13, 15):
        if result != result2:
            result2 = result
            break
        dic = []
        print "Padding: " + str(padding)
        for y in range(33, 127):
            flag = "".join([chr(0x0b + x) for x in xrange(padding)]) + ", flag: " + result + chr(y)
            p.sendline(flag)
            len1 = len(p.recvline().strip())
            if len(dic) > 0 and len1 not in dic:
                dic.append(len1)
                result += chr(33 + dic.index(min(dic)))
                print result
                break
            else:
                dic.append(len1)
    if result.endswith("}"):
        break

print result

题目二

要点：已知pow(g, x, p)、g、p，求解x

# -*- coding:utf8 -*-
from Crypto.Cipher import AES
from hashlib import sha256

p = ******
g = 2
a = ******
# F = IntegerModRing(p)
# G = F(g)
# A = F(a)
# x = discrete_log(A, G)
# print x
# x = ******
# key = pow(r, x, p)
# print key
key = ******
c = "******"
c = c.decode("hex")
aes = AES.new(sha256(str(key).encode()).digest())
print aes.decrypt(c)

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Orz