Tags: gmpy python

Rating:

## It's Prime Time! (PPC, 60p)

Description: We all know that prime numbers are quite important in cryptography. Can you help me to find some?

###ENG
[PL](#pl-version)

The server sends input as:

Hi, you know that prime numbers are important, don't you? Help me calculating the next prime!
Level 1.: Find the next prime number after 8:

And our task is to provide next prime numer after given number.
Numbers were small so we could have implemented a naive algorithm or a sieve, but instead we just used gmpy2.next_prime:

python
import re
import socket
import gmpy2
from time import sleep

def main():
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("188.166.133.53", 11059))
regex = "Level \d+\.: .* (\d+)"
initial_data = str(s.recv(4096))
print(initial_data)
while True:
sleep(1)
previous_number = int(m.group(1))
result = int(gmpy2.next_prime(previous_number))
print("result = "+str(result))
s.sendall(str(result) + "\n")
pass

main()


And after 100 examples we got a flag: IW{Pr1m3s_4r3_!mp0rt4nt}

###PL version

Serwer przysyła dane w formacie:

Hi, you know that prime numbers are important, don't you? Help me calculating the next prime!
Level 1.: Find the next prime number after 8:

A naszym zadaniem jest zwrócić kolejną liczbę pierwszą po podnanej liczbie.
Liczby były bardzo małe więc mogliśmy użyć algorytmu naiwnego albo sita, ale zamiast tego użyliśmy gotowego gmpy2.next_prime:

python
import re
import socket
import gmpy2
from time import sleep

def main():
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("188.166.133.53", 11059))
regex = "Level \d+\.: .* (\d+)"
initial_data = str(s.recv(4096))
print(initial_data)
while True:
sleep(1)

I po 100 przykładach dostaliśmy flagę: IW{Pr1m3s_4r3_!mp0rt4nt}