Baby-IQ
Category: crypto
114 points
Use this simple crypto algorithm to learn about padding and evaluate yourself on how well you understand algorithms.
baby-iq.py
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
from math import sqrt
from flag import flag
import os
import random
import base64
def chunkchunk(msg, l):
return [msg[l*i:l*(i + 1)] for i in range(0, len(msg) // l)]
def pad(msg):
r = int(sqrt(len(msg))) + 1
head = base64.b64encode(os.urandom(r**2))[:r**2 - (len(msg))]
msg = head + msg.encode('utf-8')
msg = chunkchunk(msg, r)
return [list(m) for m in msg]
def encrypt(A):
row = len(A)
col = len(A[0])
top = 0
left = 0
tmp = []
while (top < row and left < col) :
for i in range(left, col) :
tmp.append(A[top][i])
top += 1
for i in range(top, row) :
tmp.append(A[i][col - 1])
col -= 1
if ( top < row) :
for i in range(col - 1, left - 1, -1) :
tmp.append(A[row - 1][i])
row -= 1
if (left < col) :
for i in range(row - 1, top - 1, -1) :
tmp.append(A[i][left])
left += 1
result = []
for i in range(len(A)):
r = []
for j in range(len(A[0])):
r.append(tmp[i*len(A[0]) + j])
result.append(r)
return result
A = pad(flag)
for _ in range(len(A)):
_ = encrypt(A)
A = _
print('enc =', A)enc.txt
enc = [[122, 83, 52, 67, 84, 70], [89, 114, 79, 48, 67, 125], [95, 121, 114, 53, 116, 55], [123, 95, 80, 51, 52, 95], [102, 115, 114, 95, 119, 107], [52, 117, 109, 33, 97, 112]]Solution
I took the source of given baby-iq.py and changed it a bit. Copied encrypt function and reversed it as decrypt.
The result can be found below.
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
from math import sqrt
import os
import base64
def unchunkchunk(l):
enc_merged = []
for i in l:
enc_merged += i
return enc_merged
def chunkchunk(msg, l):
return [msg[l * i:l * (i + 1)] for i in range(0, len(msg) // l)]
def pad(msg):
r = int(sqrt(len(msg))) + 1
head = base64.b64encode(os.urandom(r ** 2))[:r ** 2 - (len(msg))]
msg = head + msg.encode('utf-8')
msg = chunkchunk(msg, r)
return [list(m) for m in msg]
def encrypt(A):
row = len(A)
col = len(A[0])
top = 0
left = 0
tmp = []
while (top < row and left < col):
for i in range(left, col):
tmp.append(A[top][i])
top += 1
for i in range(top, row):
tmp.append(A[i][col - 1])
col -= 1
if (top < row):
for i in range(col - 1, left - 1, -1):
tmp.append(A[row - 1][i])
row -= 1
if (left < col):
for i in range(row - 1, top - 1, -1):
tmp.append(A[i][left])
left += 1
result = []
for i in range(len(A)):
r = []
for j in range(len(A[0])):
r.append(tmp[i * len(A[0]) + j])
result.append(r)
return result
def decrypt(A):
row = len(A)
col = len(A[0])
top = 0
left = 0
col2 = 0
row2 = 0
tmp = [[0 for i in range(col)] for j in range(row)]
while (top < row and left < col):
for i in range(left, col):
tmp[top][i] = A[col2][row2]
row2 = row2 + 1 if row2 < len(A[0]) - 1 else 0
col2 = col2 + 1 if row2 == 0 else col2
top += 1
for i in range(top, row):
tmp[i][col - 1] = A[col2][row2]
row2 = row2 + 1 if row2 < len(A[0]) - 1 else 0
col2 = col2 + 1 if row2 == 0 else col2
col -= 1
if (top < row):
for i in range(col - 1, left - 1, -1):
# tmp.append(A[row - 1][i])
tmp[row - 1][i] = A[col2][row2]
row2 = row2 + 1 if row2 < len(A[0]) - 1 else 0
col2 = col2 + 1 if row2 == 0 else col2
row -= 1
if (left < col):
for i in range(row - 1, top - 1, -1):
tmp[i][left] = A[col2][row2]
row2 = row2 + 1 if row2 < len(A[0]) - 1 else 0
col2 = col2 + 1 if row2 == 0 else col2
# tmp.append(A[i][left])
left += 1
tmp = unchunkchunk(tmp)
result = []
for i in range(len(A)):
r = []
for j in range(len(A[0])):
r.append(tmp[i * len(A[0]) + j])
result.append(r)
return result
enc = [[122, 83, 52, 67, 84, 70],
[89, 114, 79, 48, 67, 125],
[95, 121, 114, 53, 116, 55],
[123, 95, 80, 51, 52, 95],
[102, 115, 114, 95, 119, 107],
[52, 117, 109, 33, 97, 112]]
for _ in range(len(enc)):
enc = decrypt(enc)
flag = bytes(unchunkchunk(enc))
print('Flag: {}'.format(flag))Output:
Flag: b'zS4CTF{34sY_CryPtO_7a5k_f0r_w4rmup!}'Flag
S4CTF{34sY_CryPtO_7a5k_f0r_w4rmup!}