ISCC2024 WriteUp

msic Funzip

Funzip writeup解题思路

1.打开题目发现是一个base64

2.看了一遍后发现他不是很全于是写一个脚本进行补全

wf = open("5.txt", "w")

with open("1 (2).txt", "r") as f:

data = f.read()

data = data.splitlines()

for line in data:

missing_padding = len(line) % 4

if missing_padding != 0:

line += "=" * (4 - missing_padding)

wf.write(line + "\n")

wf = open("5.txt", "w")

with open("1 (2).txt", "r") as f:
    data = f.read()
    data = data.splitlines()

for line in data:
    missing_padding = len(line) % 4
    if missing_padding != 0:
        line += "=" * (4 - missing_padding)
    wf.write(line + "\n")

3.补全后的base64

4.根据之前的做题经验发现这是一个隐写于是再写一个脚本去解开隐写得出flag

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VTFWT1Fsb3diRVJSVjJSS1VUQkpOVkV5WXpsUVVUQQ=='''

e=q.splitlines()

binstr=""

base64="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"



for i in e:

    if i.find("==") > 0:

        temp = bin((base64.find(i[-3]) & 15))[2:]  

        binstr += "0" * (4 - len(temp)) + temp 

    elif i.find("=") > 0:

        temp = bin((base64.find(i[-2]) & 3))[2:]

        binstr += "0" * (2 - len(temp)) + temp  



str = ""

for i in range(0, len(binstr), 8):

    str += chr(int(binstr[i:i+8], 2)) 



print(str)