Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!rutgers!sri-unix!hplabs!hpcea!hpccc!hpl-opus!jewett From: jewett@hpl-opus.HP.COM (Bob Jewett) Newsgroups: sci.crypt Subject: Re: New PubKey System Coming Message-ID: <1090002@hpl-opus.HP.COM> Date: Thu, 8-Jan-87 13:52:48 EST Article-I.D.: hpl-opus.1090002 Posted: Thu Jan 8 13:52:48 1987 Date-Received: Fri, 9-Jan-87 21:33:29 EST References: <3859@utcsri.UUCP> Organization: HP Labs, Instrument Tech. Dept. Lines: 27 > / sci.crypt / gwyn@brl-smoke.ARPA (Doug Gwyn ) / 8:56 am Jan 7, 1987 / > - It is virtually impossible for an outsider to break the > - decrypting key, which consists of a binary string of more than 1,000 > - characters, Mr. Vanstone said. > - "It would take more than a billion years, working with the > - fastest computers available, to break just one key," he said. > > I hope it is obvious to most readers of this newsgroup that > the above claim is bullshit. Pretty strong statement, Doug. Let's look a little closer... If they use RSA, and the product number (public key) is 1000 bits long, we can ask how log it would take to factor the public key, or alternatively, how much it would cost. It presently costs about US$100000 to factor a 100 digit number. The cost increases by a factor of ten for each ten digits. 1000 bits is 300 digits, so the cost of factoring the public key would be US$10000000000000000000000000. I think that's enough to deter even the NSA. For a Cray 2, assuming a cost of operation of US$10Meg per year, this works out to 10^18 years. This is > 1 billion. Of course there are some hazy points. Do they use RSA, are there fast methods of breaking RSA (or factoring), is "1000 characters" actually 1000 bits, is my cost estimate and scaling formula correct, etc? The point is that Mr. Vanstone's statement, while unclear as quoted, is not unreasonable.