Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watmath!clyde!rutgers!seismo!mimsy!eneevax!umd5!brl-adm!brl-smoke!gwyn From: gwyn@brl-smoke.UUCP Newsgroups: sci.crypt Subject: Re: Cheap more-or-less one-time-pads Message-ID: <5846@brl-smoke.ARPA> Date: Fri, 8-May-87 03:28:41 EDT Article-I.D.: brl-smok.5846 Posted: Fri May 8 03:28:41 1987 Date-Received: Sat, 9-May-87 08:14:04 EDT References: <57@decvax.UUCP> Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) ) Distribution: world Organization: Ballistic Research Lab (BRL), APG, MD. Lines: 18 Keywords: DES In article <57@decvax.UUCP> minow@decvax.UUCP (Martin Minow) writes: >Have I forgotten something? What you described amounts to a "book code". Unlike real books, CDs are quite amenable to computerization. While this is an advantage for the encryptor, it is an even bigger advantage for the analyst. The real problem is that, despite initial appearances, the key space is rather small. A dedicated cryppy would have a complete CD library; he would also preprocess the library to develop a file of characteristic statistical signatures so that he could relatively quickly determine which key you actually used for your message. One-time pad systems really MUST use truly random keys to guarantee unbreakability. The keys could be distributed as magtapes, CD disks, and so forth, but you need to limit distribution to just the intended communicators, not record stores. The best scheme would be to have the key automatically destroyed as it is used.