- cypherpunks-legacy@lists.ogf.org

Re: Compressed/Encrypted Voice using Modems
by Phiber Optik 09 Feb '93

09 Feb '93

> > So, what is a 'typical' S/N ratio for a POTS call? > > Good question. By the way, I think I may have slipped and reversed my units in signal to noise ratios. A minor typo. The signal and noise are in dBm's (decibels per milliwatt), and the resultant S/N ratio is in dB's (decibels). A little background info: the ideal voice frequency channel has a FLAT amplitude/frequency response, that is, it's uniform over the pass-band (approx. .3 to 3kHz). In reality, this isn't the case, but we want it to be as close as possible. In North America, we test signal level at 1kHz (precisely 1004). If we input a signal at -10dBm, we want -10dBm at the output. The common type of test-line in the phone system for this purpose is nicknamed the "milliwatt test", and is a continuous interrupted 1004Hz tone. Depending on the nature of the channel being tested, there would be acceptable guidelines that would have to be met with. For example, a typical S/N value might be 40dB, based on customer satisfaction of line quality. Another common test-line in wide use is the type-105 ATMS, Automatic Trans- mission Measurement System (nicknamed "responders"). Signalled with Multi- Frequency tones (MF), it is capable of doing: signal at 404, 1004, and 2804Hz at two different levels (for comparative S/N ratios at the low, middle, and top portion of the passband, a major improvement on the older "sweep tone" method), and two types of noise (again I remember at two levels), the most common being C-message noise (dBrnC). C-message weighting is the modern means of measuring signal and noise amplitude/frequency response, based on today's telephone handsets (there were two previous major Western Electric weightings, 144 and F1A, now obsoleted). The standard reference frequency (1004Hz), was established by picking a frequency in the pass-band where the signal level was JUST discernible by the human ear, and is between -85 to -90dBm, and the derived units are positive. We consider the noise measurement knowing the zero reference (ideally 0 dB difference at the reference frequency), and the weighting characteristics of the C-message standard telephone handset. Unfortunately, I can't draw you a chart, but there is a characteristic curve of frequency-response in weightings of channel noise for the C-message handset. Noise measurement instruments have artificial filters that simulate the response of the modern handset. Am I making any sense? I hope I am. What I'm getting at, is that the accept- able guidelines of signal and noise levels is simply based upon a chosen standard handset sensitivity. Got it? C'mon! It's easy!

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Re: SunExpress to expand "unlockable" software distribution
by fnerd＠smds.com 09 Feb '93

09 Feb '93

gnu(a)toad.com (John Gilmore) says: >It would probably be a public service if some interested parties were >to determine the ``encryption'' method that Sun Express, the standard >Sun ``license manager'', and other packages use. At the moment, the >details of these technologies are not described in the public >literature (as far as I know). > >Rather than have these companies discover years too late that their >"unlockable" software is really unlockable by anyone who understands >cryptography, it'd be better for them to learn it this year, while >they are still handling low volumes of programs that way. Also maybe >they will stop dumping these programs-that-you-have-but-must-pay-to-run on us. > > John I was in a meeting where the license manager technology was explained from a semi-technical, semi-business point of view. o There's a standard that many companies are using. It's for the rpc interface between licensed programs and license managers. The program calls the manager, tells it a couple things, and asks, is it okay for me to run? o License managers vary in the kinds of licenses they can support. There's enough variety of license possibilities to make your head swim. o License managers generally work from "licenses," which are text files on your computer that describe the terms of particular licenses in a license-manager-specific language. o I think they use RSA, MD5, etc., for instance in signing logs that they keep. o License-managers are themselves expensive and licensed, with a variety of up-front/per platform/per site/per end user/per developer license combinations as well as the feature variety I mentioned. I could probably find out what public documents exist if nobody else on the list knows. -fnerd quote me fnerd(a)smds.com (FutureNerd Steve Witham)

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White House Mail
by Don Henson 09 Feb '93

09 Feb '93

Can someone repost the email address for the White House. I seem to have misplaced my copy. :( Don Henson PGP key on request

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Re: Modem Based Crypto Telephones
by Phil Karn 08 Feb '93

08 Feb '93

It's true, dialup modems are becoming so fast that low bit rate vocoders may well prove unnecessary for a secure phone with good voice quality. But vocoders are still handy for allowing the use of a slower modem (e.g., over impaired lines, such as those with a lot of taps :-)) and for freeing up bandwidth that you might want to use for other purposes (e.g., data). Phil

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Re: Compressed/Encrypted Voice using Modems
by Phil Karn 08 Feb '93

08 Feb '93

Sounds like we need a new unit that specifically means "bits/sec" but is easier to say. How about "Shannons", as in "I just bought a 14.4 kiloshannon modem". :-) Phil

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Re: Compressed/Encrypted Voice using Modems
by jim＠tadpole.com 08 Feb '93

08 Feb '93

The shannon limit of 22kpbs has something to do with the frequency response of a 'standard' (old, non digital) POTS phone line. But you should know, you're Phil Karn (and I'm not.) Jim

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CLINTON'S E-MAIL HOAX
by John.Nieder＠f33.n125.z1.FIDONET.ORG 08 Feb '93

08 Feb '93

from: john.nieder(a)f33.n125.z1.fidonet.org >The White House writes: > PS: If you did not include your U.S. mail return address in your > message and you want a reply, please send your message again and > include that information. ] Well this is completely useless, isn't it.. If we imagine this ]logically we can see masses of e-mail entering the White House while snail ]mail trickles out... Definately [sic] a buffer problem |-]. At least ]they're trying, I suppose... ]DrZaphod The White House E-Mail gambit is a gimmick without substance. One - according to a previous Cypherpunks post, the e-mail isn't getting through; two - they want mailing addresses for acknowledgement, which is absurd for any number of obvious reasons (take your pick or come up with your own); finally (this is the _real_ kicker), tonight's news informs me that the Clinton White House is making a "symbolic" cost-cutting gesture by reducing staff "up to 25%." Where will these reductions come from? "The reductions will come mostly from staff whose job is to respond to mail from the public." This hoax is the biggest joke since Rush Limbaugh gave out his CompuServe address. A collective Cypherpunk e-letter to Slick? Let's not & say we did...[yawn!] JN ["The White House is informed that no group or persons are authorized by Mr. Nieder to speak on his behalf, including Mr. Clinton."] ... Source: "Deniable Asset Squares Up" - San Francisco, CA --- Blue Wave/Opus v2.12 [NR] -- John Nieder - via FidoNet node 1:125/555 UUCP - ...!uunet!hoptoad!kumr!fidogate!33!John.Nieder INTERNET - John.Nieder(a)f33.n125.z1.FIDONET.ORG

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*Private* E-Mail to White House
by ALAN DORN HETZEL JR 08 Feb '93

08 Feb '93

Maybe we should suggest as a central theme to our first letter that the White House should set up one or more PGP keys of their own. The main purpose being that then one could E-Mail someone in the administration with reasonable certainty that the message could neither be intercepted nor tampered with. Of course, once they get around to responding via e-mail, it works both ways.... Alan Dorn Hetzel, Jr. dorn(a)indigo.mese.com p.s. I'm not wired up with PGP yet because i'm using a VAX running VMS and DECUS UUCP. Has anybody ported PGP to this platform? Ideas?

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No Subject
by root＠extropia.wimsey.com 08 Feb '93

08 Feb '93

Hi - I tried to use the anon.penet.fi remailer and got a warning that some people had hacked it to find out for which anonymous ID any user had. It sounded like they would forge mail from the person they wanted to find out about, have it go through penet, and then go to themselves. Then they could look and see what anonymous ID it seemed to come from. This has been fixed by making people register a password with the remailer and then use it whenever they want to forward mail. I'd like to see some discussion here about this problem so that other remailers can avoid it.

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Remailers (List available)
by uni＠acs.bu.edu 08 Feb '93

08 Feb '93

I was hopeing to find a list of the remailers available that use PGP for traffic encryption. I noticed that the PAX scripts were made public recently, does anyone plan to employ them at any of the current remailing sites? Despite its problems, I thought PAX was on the right track with regard to tactics.... Comments?

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