36 lines
986 B
Python
36 lines
986 B
Python
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#!/usr/bin/env nix-shell
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#!nix-shell -i python3 -p python3 python3Packages.pwntools python3Packages.pycryptodome
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from pwn import *
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from Crypto.Util.number import long_to_bytes
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def decipher(r: tube, ciphertext: bytes) -> str:
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r.recvuntil(b'Give me ciphertext to decrypt: ')
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r.sendline(ciphertext)
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r.recvuntil(b'Here you go: ')
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return r.recvline().strip()
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def main():
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addr, port, *_ = "mercury.picoctf.net 33780".split(" ")
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r = remote(addr, int(port))
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r.recvuntil(b'Good Luck!\n\n\n')
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n = int(r.recvline().split(b' ')[1].strip())
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e = int(r.recvline().split(b' ')[1].strip())
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enc = int(r.recvline().split(b' ')[1].strip())
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print(f"{n=}")
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print(f"{e=}")
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print(f"{enc=}")
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padding = 2
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encrypted_padding = pow(padding, e, n)
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payload = (enc * encrypted_padding)
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output = decipher(r, str(payload).encode())
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flag = long_to_bytes(int(output) // padding).decode()
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print(flag)
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if __name__ == "__main__":
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main()
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