Scrambled: RSA

scrambled_rsa/sol.py

@@ -0,0 +1,43 @@
+#!python3
+from pwn import *
+from sage.all import Integer
+from string import ascii_lowercase, ascii_uppercase, digits
+
+conn = remote("mercury.picoctf.net", 4484)
+
+conn.recvuntil(b": ")
+flag = conn.recvline().strip()
+conn.recvuntil(b"n: ")
+n = Integer(conn.recvline())
+conn.recvuntil(b"e: ")
+e = Integer(conn.recvline())
+
+def remote_encrypt(msg):
+    conn.recvuntil(b"me: ")
+    conn.sendline(msg)
+    conn.recvuntil(b"go: ")
+    return conn.recvline().strip()
+
+#'''
+charset = ascii_lowercase + digits + "_" + ascii_uppercase + "{}"
+C_residue = flag
+msg = b""
+known_encs = []
+P = log.progress("bruteforcing message")
+while len(C_residue) > 0:
+    P.status(msg.decode())
+    for new_char in charset:
+        new_char = new_char.encode()
+        new_msg = msg + new_char
+        new_enc = remote_encrypt(new_msg)
+        for enc in known_encs:
+            new_enc = new_enc.replace(enc, b"")
+        if new_enc in C_residue:
+            msg += new_char
+            known_encs.append(new_enc)
+            C_residue = C_residue.replace(new_enc, b"")
+            break
+P.success(msg.decode())
+log.info("message: {}".format(msg))
+#'''
+