SvATTT2017 - Crypto 1

cipher.txt

a309cf189cdee501959940feba153461eef5201e00639caac3bbdf4c2f8295703975dd2786c6b8a1ad03ae204ac0693e5886dca64f1d717b6840985f10caca728f5725e60fa7b69f1f968d447b2d6199ae3ce0be378cc33155a2d94c8c22438 2ec106245f4b07a2a99f6949750ff48e97cbe8434ec0038e0e2bcce7cc7d9f0305a5a5358637e5d31158fecf2ab6306be80e9eabc219673d974db197ccbf97afec3d27165ff7a5d3af573d6e973b6c8f124e50f8bf2e111595c07560f40097b4 5f0f2fbe27cff7785ecb9e834b9201c086ab6a2a211e3a2807bce8db68bf452369e5610f463225f41a9f254f46ee6816f53d7e6496a84eab08fded7f9bba2aadad25cf6e9b95c6a5a4f355d9b580ba496fa824fcc1a082f364625b1a871117ba 6844981dbfd05b1912e7f20adcb108d2ad134ed313bc3d24cc18a0a41525b258ab0412d928a7a9529299154d62d1e92822f1081e645512f609d9bed0f8c2f2de56f1fb0cbfe49e7dffd4989d08fd07f627b7bb4c4388b632d0ff327adcf2cd2d 2ecc34bccbb70ace772e9563eeb01fb50e8321e672dacaf1e79376882e7a6ea3c9088504f35922ea3d3f571b5cac64f9dd6c2dd66c27fb02295b97e0013425c9fd898ac609d4941e99dc51fc6a5e3c11dffcdeb905d64bcfc97915e1fab69cf0 76edfba1dacef5a8a95fceb46be785a4f6c31eda3f2aef3bb63d2107c547962ab0dd32490589bd93a5661620319becd11714a1cde3060d229f6e42a56ca961f611ba868606141d627e2451f75ac090cf066187c9660f040211f6ef16cdb6197d afad9c5327b0646c04918e02b4e7c0a09007850af04914c382e6eb5ddbe4ce0f959a581f28802d5e68462362d527fe8dce858a7ca80f825413d73f2ade27e0b21e3b016bfac30a749c0bc208cf960f6f00c8a3f0a9fc0164cbbfdf74da7cc147

encrypt.py

import gmpy2
from ctf import MESSAGES

N = 1552518092300708935148979488462502555256886017116696611139052038026050952686376886330878408828646477971459063658923221258297866648143023058142446317581796810373905913084934869211153276980011573717416472395713363686571638755823503877
e = 3
BS = 32

to_int = lambda text: int(''.join(x.encode('hex') for x in text), 16)

c = 0L
cipher = []
for chunk in [MESSAGES[i:i + BS] for i in range(0, len(MESSAGES), BS)]:
    c1 = int(hex(c)[2:-1][:BS*2+1], 16)
    c = gmpy2.powmod(c1 + to_int(chunk), e, N)
    cipher.append(hex(c)[2:])

with open('cipher.txt', 'w') as f:
    f.write(' '.join(cipher))