cscg ist super

2026/cscg/crypto/intro1/solve.py

@@ -0,0 +1,34 @@
+from pwn import context, args, process, remote, success, xor
+
+context.update(arch='amd64', os='linux', log_level='info')
+
+URL = 'iaet6burymdllg3rflxg4ym7vk-1024-intro-crypto-1.challenge.cscg.live'
+PORT = 443
+
+def start():
+    if args.REMOTE:
+        return remote(URL, PORT, ssl=True)
+    else:
+        return process(['python3', './main.py'])
+
+io = start()
+
+payload_len = 512
+io.sendlineafter(b"Enter some plaintext (hex): ", (b"00" * payload_len))
+
+keystreams = []
+for i in range(256):
+    line = io.recvline()
+    ks = bytes.fromhex(line.strip().split(b" ")[-1].decode())
+    keystreams.append(ks)
+
+io.recvuntil(b"Flag: ")
+flag_enc = bytes.fromhex(io.recvline().strip().decode())
+
+io.close()
+
+for ks in keystreams:
+    candidate = xor(flag_enc, ks[:len(flag_enc)])
+    if b"CSCG{" in candidate or b"flag{" in candidate:
+        success(f"Found Flag: {candidate.decode()}")
+        break