crypto/no_padding_no_problem

crypto/no_padding_no_problem/solve.py

@@ -0,0 +1,35 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -i python3 -p python3 python3Packages.pwntools python3Packages.pycryptodome
+
+from pwn import *
+from Crypto.Util.number import long_to_bytes
+
+def decipher(r: tube, ciphertext: bytes) -> str:
+    r.recvuntil(b'Give me ciphertext to decrypt: ')
+    r.sendline(ciphertext)
+    r.recvuntil(b'Here you go: ')
+    return r.recvline().strip()
+
+def main():
+    addr, port, *_ = "mercury.picoctf.net 33780".split(" ")
+    r = remote(addr, int(port))
+
+    r.recvuntil(b'Good Luck!\n\n\n')
+
+    n = int(r.recvline().split(b' ')[1].strip())
+    e = int(r.recvline().split(b' ')[1].strip())
+    enc = int(r.recvline().split(b' ')[1].strip())
+    print(f"{n=}")
+    print(f"{e=}")
+    print(f"{enc=}")
+
+    padding = 2
+    encrypted_padding = pow(padding, e, n)
+
+    payload = (enc * encrypted_padding)
+    output = decipher(r, str(payload).encode())
+    flag = long_to_bytes(int(output) // padding).decode()
+    print(flag)
+
+if __name__ == "__main__":
+    main()