xx
程序开始验证输入长度为19位。
取前4位(作为后面加密的key),验证这4位都在‘qwertyuiopasdfghjklzxcvbnm1234567890‘中。
将key用0填充为16位
调用xxtea进行加密,加密结果再进行置换。
再进行异或操作
最终比较
wp
import struct_DELTA = 0x9E3779B9def _long2str(v, w):
n = (len(v) - 1) << 2
if w:
m = v[-1]
if (m < n - 3) or (m > n): return ''
n = m
s = struct.pack('<%iL' % len(v), *v)
return s[0:n] if w else sdef _str2long(s, w):
n = len(s)
m = (4 - (n & 3) & 3) + n
s = s.ljust(m, b"\0")
v = list(struct.unpack('<%iL' % (m >> 2), s))
if w: v.append(n)
return vdef encrypt(str, key):
if str == '': return str
v = _str2long(str, True)
k = _str2long(key.ljust(16, b"\0"), False)
n = len(v) - 1
z = v[n]
y = v[0]
sum = 0
q = 6 + 52 // (n + 1)
while q > 0:
sum = (sum + _DELTA) & 0xffffffff
e = sum >> 2 & 3
for p in range(n):
y = v[p + 1]
v[p] = (v[p] + ((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4) ^ (sum ^ y) + (k[p & 3 ^ e] ^ z))) & 0xffffffff
z = v[p]
y = v[0]
v[n] = (v[n] + ((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4) ^ (sum ^ y) + (k[n & 3 ^ e] ^ z))) & 0xffffffff
z = v[n]
q -= 1
return _long2str(v, False)def decrypt(str, key):
if str == '': return str
v = _str2long(str, False)
k = _str2long(key.ljust(16, b"\0"), False)
n = len(v) - 1
z = v[n]
y = v[0]
q = 6 + 52 // (n + 1)
sum = (q * _DELTA) & 0xffffffff
while (sum != 0):
e = sum >> 2 & 3
for p in range(n, 0, -1):
z = v[p - 1]
v[p] = (v[p] - ((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4) ^ (sum ^ y) + (k[p & 3 ^ e] ^ z))) & 0xffffffff
y = v[p]
z = v[n]
v[0] = (v[0] - ((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4) ^ (sum ^ y) + (k[0 & 3 ^ e] ^ z))) & 0xffffffff
y = v[0]
sum = (sum - _DELTA) & 0xffffffff
return _long2str(v, True)
tg=[0xCE, 0xBC, 0x40, 0x6B, 0x7C, 0x3A, 0x95, 0xC0, 0xEF, 0x9B, 0x20, 0x20, 0x91, 0xF7, 0x02, 0x35,
0x23, 0x18, 0x02, 0xC8, 0xE7, 0x56, 0x56, 0xFA ]
order=[2,0,3,1,6,4,7,5,10,8,11,9,14,12,15,13,18,16,19,17,22,20,23,21]
flag=[0]*24
for i in range(23,-1,-1):
for j in range(i//3):
tg[i]^=tg[j]
print('逆异或操作后:'+' '.join(map(hex,tg)))
for i in range(24):
flag[order[i]]=tg[i]
print('逆加密字符串替换后:'+' '.join(map(hex,flag)))
x=decrypt(bytes(flag),'flag'.encode())
print(x)
逆异或操作后:0xce 0xbc 0x40 0xa5 0xb2 0xf4 0xe7 0xb2 0x9d 0xa9 0x12 0x12 0xc8 0xae 0x5b 0x10 0x6 0x3d 0x1d 0xd7 0xf8 0xdc 0xdc 0x70
逆加密字符串替换后:0xbc 0xa5 0xce 0x40 0xf4 0xb2 0xb2 0xe7 0xa9 0x12 0x9d 0x12 0xae 0x10 0xc8 0x5b 0x3d 0xd7 0x6 0x1d 0xdc 0x70 0xf8 0xdc
b’flag{CXX_and_++tea}‘
xxtea算法参考: