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DeadpoolAndObjectOrientedProgramming / icectf-2016

IceCTF 2016 repo
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Stage 2 - RSA? #22

Closed ikornaselur closed 8 years ago

ikornaselur commented 8 years ago

Description

John was messing with RSA again... he encrypted our flag! I have a strong feeling he had no idea what he was doing however, can you get the flag for us? flag.txt

Solution

Flag is: IceCTF{falls_apart_so_easily_and_reassembled_so_crudely}

ikornaselur commented 8 years ago

A script is running at the moment to crack the RSA encryption.. giving it some time before revisiting with another solution.

ikornaselur commented 8 years ago 
import gmpy

N = 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

e = 0x1

c = 0x4963654354467b66616c6c735f61706172745f736f5f656173696c795f616e645f7265617373656d626c65645f736f5f63727564656c797d

orig = c

def n2s(n):
    """
    Number to string.
    """
    s = hex(n)[2:].rstrip("L")
    if len(s) % 2 != 0:
        s = "0" + s
    return s.decode("hex")

while True:
    m = gmpy.root(c, e)[0]
    if pow(m, e, N) == orig:
        print "pwned", n2s(m)
        break
    c += N

Takes a sec to run