crypto

Mirror

Punkty: 290

Rozwiązań: 11

You can't have a CTF without breaking RSA.

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Data:

136833849009378541177365407452586723306505444691976749004448551477492393370727121824647697026919571415516837272337651935637064315560075712848623840253845208440409394636665640222581087106974207162724930976023333788275806336989480648037228689764170323692429398688150195468592753198191312296734005651276133646591 1024
0xbb3fc9ea61c02c2b3db67a785fefe3ad16a0188839461351220deb1a2ee00af4cb3ffeb22450c6bc514cc1c9f288d8d58e965ed3eb6224817f3416b742e2ebd310ac3b639479a9f8d4021d81ffc5f63dc4fd9fe238bc3e35469949faece3ae8bf56e79bfca99a27077d2791cb9d207b613608945756e06f671d299829fa8e7e7

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Code:

import random
import string
from Crypto.Util.number import isPrime, bytes_to_long


def generate_dataset(nbits):
    bits = nbits // 4
    while True:
        A = random.randint(2 ** (bits - 1), 2 ** bits)
        B = random.randint(2 ** (bits - 1), 2 ** bits)
        p = A + (B << bits)
        if isPrime(p):
            q = B + (A << bits)
            if isPrime(q):
                return p, q


def pad(flag, nbits):
    missing = nbits // 8 - len(flag)
    return flag + ''.join(random.choices(string.ascii_letters, k=missing)).encode()


def main():
    print('please wait a while...')
    nbits = 1024
    p, q = generate_dataset(nbits)
    n = p * q
    print(n, nbits)
    flag = bytes_to_long(pad(open("flag.txt", "rb").read(), nbits))
    print(hex(pow(flag, 65537, n)))


main()

Format flagi: ecsc{litery_cyfry_i_znaki_specjalne}.
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