新手ctf逆向————BUUCTF [MRCTF2020]Transform

扔进ida

可以看出19行到24行是主要变换，然后与一串字符串进行比较，非常简单

写脚本

脚本也是从尾巴写到头，都逆过来就是了，从那个字符串与另一个字符串进行异或，然后根据另一串字符串进行重新排列

dword40 = [8,0x0e,0x1c,0x1a,0x12,8,0x1f,5,0x19,2,0x15,0x14,0x13,0x0d,4,0x16,0x1b,0x1e,0x0b,0x1d,0x20,0x11,3,0x10,1,6,0x0c,0x18,7,0x17,0x0f,0x0a,9][::-1]
bytee0 = [0x3f,0x4d,0x62,0x6f,0x45,0x5c,0x3c,0x65,0x7e,0x6b,0x41,0x79,0x57,0x4c,0x7e,0x42,0x66,0x2a,0x2d,0x7b,0x42,0x5d,0x5e,0x57,0x79,0x53,0x52,0x3c,0x2b,0x75,0x7f,0x7b,0x79,0x67][::-1]
byte40 = [0 for i in range(33)]
v6 = [0 for k in range(33)]
for j in range(32):
    byte40[j] =bytee0[j]^dword40[j]
    v6[dword40[j]] = byte40[j]
print(''.join([chr(l) for l in v6]))

flag{Tr4nsp0sltiON_Clph3r_1s_3z}