Description
We all know that prime numbers are quite important in cryptography. Can you help me to find some?
Solution
Connecting to the running service, I was greated with a message asking for the next prime number after [number]
So with some quick python hackery I ended up with this code.
#!/usr/bin/env python
from pwn import *
def get_next_prime(number):
"""Get next prime after number"""
for num in range(number+1, number*2):
if num > 1:
for y in range(2,num):
#print '> num %% y = %d %% %d ='%(num,y),(num % y)
if (num % y) == 0:
break
else:
return num
host = '188.166.133.53'
port = 11059
r = remote(host, port)
r.recv(1024)
while True:
orig_data = r.recv(1024)
data = orig_data.split(' ')[-1]
log.info(orig_data)
number = int(data.strip().rstrip(':'))
next_prime = str(get_next_prime(number))
log.info('Next prime after %d is %s'%(number, next_prime))
r.send(next_prime)
log.info(r.recv(1024))
r.close()It ran for a little bit before crashing, which I expected, and returning the flag.
Flag: IW{Pr1m3s_4r3_!mp0rt4nt}