1 files changed, 26 insertions, 0 deletions
diff --git a/solve/solve.py b/solve/solve.py
new file mode 100644
index 0000000..68b58f3
--- /dev/null
+++ b/solve/solve.py
@@ -0,0 +1,26 @@
+#!/usr/bin/env python3
+
+from Crypto.PublicKey import RSA
+from Crypto.Util.number import long_to_bytes
+from math import isqrt, inf
+from tqdm import tqdm
+
+pubkey = RSA.importKey(open("pubkey.pem").read())
+
+# Small primes can be found with naive approach.
+
+for i in tqdm(range(3, isqrt(pubkey.n), 2), total=inf):
+    if pubkey.n % i == 0:
+        p = i
+        break
+else:
+    raise
+
+q = pubkey.n // p
+phi = (p-1)*(q-1)
+d = pow(pubkey.e, -1, phi)
+
+ciphertext = int(open("message.txt").read())
+plaintext = pow(ciphertext, d, pubkey.n)
+
+print(long_to_bytes(plaintext).decode())