buuctf

注意，strcat拼接时，是以小端序方式拼接的，0x……LL中的LL指的是long long类型，从右到左读字符。

from binascii import a2b_hex
import gmpy2
t1 = '4E44434C53'
key = 'ADSFK' + a2b_hex(t1).decode()
v5=len(key)
v3=0
keyt=""
for i in range(v5):
    if ord(key[v3 % v5]) > 64 and ord(key[v3 % v5])<= 90:
        keyt += chr(ord(key[v3 % v5]) + 32)
        v3=v3+1


print(keyt)
text='killshadow'
dict='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
flag=''
for i in range(len(text)):
    for ch in dict:
        if ord(text[i]) == (ord(ch) - 39 - ord(keyt[i % v5])+ 97) % 26 + 97:
            flag+=ch
            break
print(flag)