srdnlen2026 quals started

2026/srdnlen_quals/forensic/chapter1/solve.py

@@ -0,0 +1,18 @@
+docbody = [206,56,8,128,209,47,2,149,202,34,95,128,226,41,92,156,
+           142,38,51,153,137,57,51,218,211,21,88,130,201,121,30,128,
+           137,62,93,152,142,55]
+
+# Known prefix "srdnlen{"
+prefix = "srdnlen{"
+
+# Derive key bytes from known prefix
+key = []
+for i, c in enumerate(prefix):
+    key.append(docbody[i] ^ ord(c))
+
+print(f"Derived key bytes: {key}")
+print(f"Derived key chars: {''.join(chr(k) for k in key)}")
+
+# Decode full docbody with cycling key
+result = ''.join(chr(docbody[i] ^ key[i % len(key)]) for i in range(len(docbody)))
+print(f"\nDecoded flag: {result}")