2018强网杯记录

 

1 签到题

 

2welcome

下载文件，发现是一个BMP图片文件。

于是使用Stegsolve工具分离，发现，得到flag

 

3 streamgame1

上脚本1

#! /usr/bin/env python3

# coding:utf8

def lfsr(R,mask):

    output = (R << 1) & 0xffffff

    i=(R&mask)&0xffffff

    lastbit=0

    while i!=0:

        lastbit^=(i&1)

        i=i>>1

    output^=lastbit

    return (output,lastbit)

mask = 0b1010011000100011100

f=open("./key","rb")

c=f.read()

f.close()

count = -1

while count <= 0b1111111111111111111:

    count += 1

    print(count)

    R = count

    for i in range(12):

        tmp=0

        for j in range(8):

            (R,out)=lfsr(R,mask)

            tmp=(tmp << 1)^out

        if tmp != c[i]:

            break

        if i == 11:

            print('succeed')

            print('flag{%s}' % bin(count)[2:])

            exit(0)

 

           

4 streamgame2

上脚本2

#! /usr/bin/env python3

# coding:utf8

def lfsr(R,mask):

    output = (R << 1) & 0xffffff

    i=(R&mask)&0xffffff

    lastbit=0

    while i!=0:

        lastbit^=(i&1)

        i=i>>1

    output^=lastbit

    return (output,lastbit)

mask = 0x100002

f=open("./key","rb")

c=f.read()

f.close()

count = -1

while count <= 0b111111111111111111111:

    count += 1

    if count % 10000 == 0:

        print(count)

    R = count

    for i in range(12):

        tmp=0

        for j in range(8):

            (R,out)=lfsr(R,mask)

            tmp=(tmp << 1)^out

        if tmp != c[i]:

            break

        if i == 11:

            print('succeed')

            print('flag{%s}' % bin(count)[2:])

            exit(0)

 

           

5 streamgame4

上脚本3

#! /usr/bin/env python3

# coding:utf8

def lfsr(R,mask):

    output = (R << 1) & 0xffffff

    i=(R&mask)&0xffffff

    lastbit=0

    while i!=0:

        lastbit^=(i&1)

        i=i>>1

    output^=lastbit

    return (output,lastbit)

mask = 0b1010011000100011100

 

f=open("./key","rb")

c=f.read()

f.close()

count = -1

while count <= 0b1111111111111111111:

    count += 1

    #print(count)

    R = count

    for i in range(12):

        tmp=0

        for j in range(8):

            (R,out)=lfsr(R,mask)

            tmp=(tmp << 1)^out

        if tmp != c[i]:

            break

        if i == 11:

            print('succeed')

            print('flag{%s}' % bin(count)[2:])

            exit(0)

 

6 web签到题

因为每次在网页里，都有网页代码的提示，三次都是绕过。

第一次绕过是利用php，==的弱等于

240610708 和 QNKCDZO 

第二次：传递数组，越过

第三次：利用碰撞试验，