- cypherpunks-legacy - lists.cpunks.org

The role of pools
by Miron Cuperman 10 Feb '93

10 Feb '93

A pool is used for *replying* to anon mail. The problem is that it's hard to build a system that allows replies to anon email and still maintains absolute security. One way is to broadcast the reply. A pool does just that - it's basically a mailing list. It could be a newsgroup. Since any of the subscribers to the pool could be the intended recipient of any particular message, it would be very hard to use the pool to trace the anonymous recipient. -- Miron Cuperman <miron(a)extropia.wimsey.com> | NeXTmail/Mime ok <miron(a)cs.sfu.ca> | Public key avail AMIX: MCuperman | cyberspacecomputingcryptoimmortalitynetworkslaissezfaire

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["Joyce K. Reynolds": RFC1422 on Certificate-Based Key Management]
by fen＠genmagic.genmagic.com 10 Feb '93

10 Feb '93

Date: Tue, 09 Feb 93 20:46:59 -0500 From: James M Galvin <galvin(a)TIS.COM> Sender: pem-dev-relay(a)TIS.COM -----BEGIN PRIVACY-ENHANCED MESSAGE----- Proc-Type: 4,MIC-CLEAR Content-Domain: RFC822 Originator-ID-Asymmetric: MEYxCzAJBgNVBAYTAlVTMSQwIgYDVQQKExtUcnV zdGVkIEluZm9ybWF0aW9uIFN5c3RlbXMxETAPBgNVBAsTCEdsZW53b29k,02 MIC-Info: RSA-MD5,RSA,SdwD9j3bEJftgUxTr4Oxa2StKH4giFOjvS5ey4B578J pEMgQYtXDXhzX4eNKmV23FducCqWXBaOHL2zvK7jK5A== - ------------------------------------------------------------------------ This message digitally signed with Privacy Enhanced Mail. Get your copy of the Internet reference implementation from "pem-info(a)tis.com". - ------- Forwarded Message Message-ID: <199302092258.AA00113(a)zephyr.isi.edu> Sender: ietf-announce-request(a)IETF.CNRI.Reston.VA.US From: "Joyce K. Reynolds" <jkrey(a)isi.edu> To: IETF-Announce:;@IETF.CNRI.Reston.VA.US cc: jkrey(a)isi.edu Date: Tue, 09 Feb 93 14:56:39 PST Subject: RFC1422 on Certificate-Based Key Management - - --NextPart A new Request for Comments is now available in online RFC libraries. RFC 1422: Title: Privacy Enhancement for Internet Electronic Mail: Part II: Certificate-Based Key Management Author: S. Kent Mailbox: kent(a)BBN.COM Pages: 32 Characters: 86,085 Obsoletes: RFC 1114 This is one of a series of documents defining privacy enhancement mechanisms for electronic mail transferred using Internet mail protocols. This memo is the outgrowth of a series of meetings of the Privacy and Security Research Group of the Internet Research Task Force (IRTF) and the Privacy-Enhanced Electronic Mail Working Group of the Internet Engineering Task Force (IETF). The author would like to thank the members of the PSRG and the PEM WG for their comments and contributions at the meetings which led to the preparation of this document. The author also would like to thank contributors to the PEM-DEV mailing list ("pem-dev(a)tis.com") who have provided valuable input which is reflected in this memo. This is now a Proposed Standard Protocol. This RFC specifies an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited. This announcement is sent to the IETF list and the RFC-DIST list. Requests to be added to or deleted from the IETF distribution list should be sent to IETF-REQUEST(a)CNRI.RESTON.VA.US. Requests to be added to or deleted from the RFC-DIST distribution list should be sent to RFC-REQUEST(a)NIC.DDN.MIL. Details on obtaining RFCs via FTP or EMAIL may be obtained by sending an EMAIL message to "rfc-info(a)ISI.EDU" with the message body "help: ways_to_get_rfcs". For example: To: rfc-info(a)ISI.EDU Subject: getting rfcs help: ways_to_get_rfcs Requests for special distribution should be addressed to either the author of the RFC in question, or to NIC(a)NIC.DDN.MIL. Unless specifically noted otherwise on the RFC itself, all RFCs are for unlimited distribution. Submissions for Requests for Comments should be sent to RFC-EDITOR(a)ISI.EDU. Please consult RFC 1111, "Instructions to RFC Authors", for further information. Joyce K. Reynolds USC/Information Sciences Institute ... Below is the data which will enable a MIME compliant Mail Reader implementation to automatically retrieve the ASCII version of the RFCs. - - --NextPart Content-Type: Multipart/Alternative; Boundary="OtherAccess" - - --OtherAccess Content-Type: Message/External-body; access-type="mail-server"; server="mail-server(a)nisc.sri.com" Content-Type: text/plain SEND rfc1422.txt - - --OtherAccess Content-Type: Message/External-body; name="rfc1422.txt"; site="nic.ddn.mil"; access-type="anon-ftp"; directory="rfc" Content-Type: text/plain - - --OtherAccess-- - - --NextPart-- - ------- End of Forwarded Message -----END PRIVACY-ENHANCED MESSAGE-----

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["Joyce K. Reynolds": RFC1424 on Key Certification and Related Services]
by fen＠genmagic.genmagic.com 10 Feb '93

10 Feb '93

Date: Tue, 09 Feb 93 20:47:53 -0500 From: James M Galvin <galvin(a)TIS.COM> Sender: pem-dev-relay(a)TIS.COM -----BEGIN PRIVACY-ENHANCED MESSAGE----- Proc-Type: 4,MIC-CLEAR Content-Domain: RFC822 Originator-ID-Asymmetric: MEYxCzAJBgNVBAYTAlVTMSQwIgYDVQQKExtUcnV zdGVkIEluZm9ybWF0aW9uIFN5c3RlbXMxETAPBgNVBAsTCEdsZW53b29k,02 MIC-Info: RSA-MD5,RSA,ev2s1woCBNlMsuccJpIUAAEuV9gQZZs5hbHG3fCPYxb hxSChOjQSJRO3cIf6/GyzyJYhRt7jZDc9VH+YLuPMeg== - ------------------------------------------------------------------------ This message digitally signed with Privacy Enhanced Mail. Get your copy of the Internet reference implementation from "pem-info(a)tis.com". - ------- Forwarded Message Message-ID: <199302092258.AA00165(a)zephyr.isi.edu> Sender: ietf-announce-request(a)IETF.CNRI.Reston.VA.US From: "Joyce K. Reynolds" <jkrey(a)isi.edu> To: IETF-Announce:;@IETF.CNRI.Reston.VA.US cc: jkrey(a)isi.edu Date: Tue, 09 Feb 93 14:56:52 PST Subject: RFC1424 on Key Certification and Related Services - - --NextPart A new Request for Comments is now available in online RFC libraries. RFC 1424: Title: Privacy Enhancement for Internet Electronic Mail: Part IV: Key Certification and Related Services Author: B. Kaliski Mailbox: burt(a)rsa.com Pages: 9 Characters: 17,537 Updates/Obsoletes: none This document describes three types of service in support of Internet Privacy-Enhanced Mail (PEM): key certification, certificate- revocation list (CRL) storage, and CRL retrieval. This is one of a series of documents defining privacy enhancement mechanisms for electronic mail transferred using Internet mail protocols. This document is the product of many discussions at RSA Data Security, at Trusted Information Systems, and on the <pem-dev(a)tis.com> mailing list. This document is the product of the Privacy-Enhanced Electronic Mail Working Group. This is now a Proposed Standard Protocol. This RFC specifies an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited. This announcement is sent to the IETF list and the RFC-DIST list. Requests to be added to or deleted from the IETF distribution list should be sent to IETF-REQUEST(a)CNRI.RESTON.VA.US. Requests to be added to or deleted from the RFC-DIST distribution list should be sent to RFC-REQUEST(a)NIC.DDN.MIL. Details on obtaining RFCs via FTP or EMAIL may be obtained by sending an EMAIL message to "rfc-info(a)ISI.EDU" with the message body "help: ways_to_get_rfcs". For example: To: rfc-info(a)ISI.EDU Subject: getting rfcs help: ways_to_get_rfcs Requests for special distribution should be addressed to either the author of the RFC in question, or to NIC(a)NIC.DDN.MIL. Unless specifically noted otherwise on the RFC itself, all RFCs are for unlimited distribution. Submissions for Requests for Comments should be sent to RFC-EDITOR(a)ISI.EDU. Please consult RFC 1111, "Instructions to RFC Authors", for further information. Joyce K. Reynolds USC/Information Sciences Institute ... Below is the data which will enable a MIME compliant Mail Reader implementation to automatically retrieve the ASCII version of the RFCs. - - --NextPart Content-Type: Multipart/Alternative; Boundary="OtherAccess" - - --OtherAccess Content-Type: Message/External-body; access-type="mail-server"; server="mail-server(a)nisc.sri.com" Content-Type: text/plain SEND rfc1424.txt - - --OtherAccess Content-Type: Message/External-body; name="rfc1424.txt"; site="nic.ddn.mil"; access-type="anon-ftp"; directory="rfc" Content-Type: text/plain - - --OtherAccess-- - - --NextPart-- - ------- End of Forwarded Message -----END PRIVACY-ENHANCED MESSAGE-----

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["Joyce K. Reynolds": RFC1423 on PEM: Algorithms, Modes and Identifiers]
by fen＠genmagic.genmagic.com 10 Feb '93

10 Feb '93

Date: Tue, 09 Feb 93 20:47:29 -0500 From: James M Galvin <galvin(a)TIS.COM> Sender: pem-dev-relay(a)TIS.COM -----BEGIN PRIVACY-ENHANCED MESSAGE----- Proc-Type: 4,MIC-CLEAR Content-Domain: RFC822 Originator-ID-Asymmetric: MEYxCzAJBgNVBAYTAlVTMSQwIgYDVQQKExtUcnV zdGVkIEluZm9ybWF0aW9uIFN5c3RlbXMxETAPBgNVBAsTCEdsZW53b29k,02 MIC-Info: RSA-MD5,RSA,SZBZEw1TKP4Mj68wVUb3t1uGaXKAhRfRScqDkULDMuG WRwco4HpFmpJxuBUzPLhysLhi0Rn6D9yG+YxFnZE4bA== - ------------------------------------------------------------------------ This message digitally signed with Privacy Enhanced Mail. Get your copy of the Internet reference implementation from "pem-info(a)tis.com". - ------- Forwarded Message Message-ID: <199302092258.AA00118(a)zephyr.isi.edu> Sender: ietf-announce-request(a)IETF.CNRI.Reston.VA.US From: "Joyce K. Reynolds" <jkrey(a)isi.edu> To: IETF-Announce:;@IETF.CNRI.Reston.VA.US cc: jkrey(a)isi.edu Date: Tue, 09 Feb 93 14:56:45 PST Subject: RFC1423 on PEM: Algorithms, Modes and Identifiers - - --NextPart A new Request for Comments is now available in online RFC libraries. RFC 1423: Title: Privacy Enhancement for Internet Electronic Mail: Part III: Algorithms, Modes, and Identifiers Author: D. Balenson Mailbox: balenson(a)tis.com Pages: 14 Characters: 33,277 Obsoletes: RFC 1115 This document provides definitions, formats, references, and citations for cryptographic algorithms, usage modes, and associated identifiers and parameters used in support of Privacy Enhanced Mail (PEM) in the Internet community. This is one of a series of documents defining privacy enhancement mechanisms for electronic mail transferred using Internet mail protocols. This document is the outgrowth of a series of meetings of the Privacy and Security Research Group (PSRG) of the Internet Research Task Force (IRTF) and the PEM Working Group of the Internet Engineering Task Force (IETF). This is now a Proposed Standard Protocol. This RFC specifies an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited. This announcement is sent to the IETF list and the RFC-DIST list. Requests to be added to or deleted from the IETF distribution list should be sent to IETF-REQUEST(a)CNRI.RESTON.VA.US. Requests to be added to or deleted from the RFC-DIST distribution list should be sent to RFC-REQUEST(a)NIC.DDN.MIL. Details on obtaining RFCs via FTP or EMAIL may be obtained by sending an EMAIL message to "rfc-info(a)ISI.EDU" with the message body "help: ways_to_get_rfcs". For example: To: rfc-info(a)ISI.EDU Subject: getting rfcs help: ways_to_get_rfcs Requests for special distribution should be addressed to either the author of the RFC in question, or to NIC(a)NIC.DDN.MIL. Unless specifically noted otherwise on the RFC itself, all RFCs are for unlimited distribution. Submissions for Requests for Comments should be sent to RFC-EDITOR(a)ISI.EDU. Please consult RFC 1111, "Instructions to RFC Authors", for further information. Joyce K. Reynolds USC/Information Sciences Institute ... Below is the data which will enable a MIME compliant Mail Reader implementation to automatically retrieve the ASCII version of the RFCs. - - --NextPart Content-Type: Multipart/Alternative; Boundary="OtherAccess" - - --OtherAccess Content-Type: Message/External-body; access-type="mail-server"; server="mail-server(a)nisc.sri.com" Content-Type: text/plain SEND rfc1423.txt - - --OtherAccess Content-Type: Message/External-body; name="rfc1423.txt"; site="nic.ddn.mil"; access-type="anon-ftp"; directory="rfc" Content-Type: text/plain - - --OtherAccess-- - - --NextPart-- - ------- End of Forwarded Message -----END PRIVACY-ENHANCED MESSAGE-----

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["Joyce K. Reynolds": RFC1421 on Privacy Enhancement for Electronic Mail]
by fen＠genmagic.genmagic.com 10 Feb '93

10 Feb '93

Date: Tue, 09 Feb 93 20:46:25 -0500 From: James M Galvin <galvin(a)TIS.COM> Sender: pem-dev-relay(a)TIS.COM -----BEGIN PRIVACY-ENHANCED MESSAGE----- Proc-Type: 4,MIC-CLEAR Content-Domain: RFC822 Originator-ID-Asymmetric: MEYxCzAJBgNVBAYTAlVTMSQwIgYDVQQKExtUcnV zdGVkIEluZm9ybWF0aW9uIFN5c3RlbXMxETAPBgNVBAsTCEdsZW53b29k,02 MIC-Info: RSA-MD5,RSA,UYBpHzD3lP5l8Wi2DzdTRPWoag3lQ7NrqmF0U+cfykK VCKx5jxPRR9CaWaddI5QobfpA4hsIVA12ZpsPzmyo9g== - ------------------------------------------------------------------------ This message digitally signed with Privacy Enhanced Mail. Get your copy of the Internet reference implementation from "pem-info(a)tis.com". - ------- Forwarded Message Message-ID: <199302092257.AA29999(a)zephyr.isi.edu> Sender: ietf-announce-request(a)IETF.CNRI.Reston.VA.US From: "Joyce K. Reynolds" <jkrey(a)isi.edu> To: IETF-Announce:;@IETF.CNRI.Reston.VA.US cc: jkrey(a)isi.edu Date: Tue, 09 Feb 93 14:56:08 PST Subject: RFC1421 on Privacy Enhancement for Electronic Mail - - --NextPart A new Request for Comments is now available in online RFC libraries. RFC 1421: Title: Privacy Enhancement for Internet Electronic Mail: Part I: Message Encryption and Authentication Procedures Author: J. Linn Mailbox: 104-8456(a)mcimail.com Pages: 42 Characters: 103,894 Obsoletes: RFC 1113 This is one of a series of documents defining privacy enhancement mechanisms for electronic mail transferred using Internet mail protocols. This document is the outgrowth of a series of meetings of the Privacy and Security Research Group (PSRG) of the Internet Research Task Force (IRTF) and the PEM Working Group of the Internet Engineering Task Force (IETF). The author would like to thank the members of the PSRG and the IETF PEM WG, as well as all participants in discussions on the "pem-dev(a)tis.com" mailing list, for their contributions to this document. This is now a Proposed Standard Protocol. This RFC specifies an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited. This announcement is sent to the IETF list and the RFC-DIST list. Requests to be added to or deleted from the IETF distribution list should be sent to IETF-REQUEST(a)CNRI.RESTON.VA.US. Requests to be added to or deleted from the RFC-DIST distribution list should be sent to RFC-REQUEST(a)NIC.DDN.MIL. Details on obtaining RFCs via FTP or EMAIL may be obtained by sending an EMAIL message to "rfc-info(a)ISI.EDU" with the message body "help: ways_to_get_rfcs". For example: To: rfc-info(a)ISI.EDU Subject: getting rfcs help: ways_to_get_rfcs Requests for special distribution should be addressed to either the author of the RFC in question, or to NIC(a)NIC.DDN.MIL. Unless specifically noted otherwise on the RFC itself, all RFCs are for unlimited distribution. Submissions for Requests for Comments should be sent to RFC-EDITOR(a)ISI.EDU. Please consult RFC 1111, "Instructions to RFC Authors", for further information. Joyce K. Reynolds USC/Information Sciences Institute ... Below is the data which will enable a MIME compliant Mail Reader implementation to automatically retrieve the ASCII version of the RFCs. - - --NextPart Content-Type: Multipart/Alternative; Boundary="OtherAccess" - - --OtherAccess Content-Type: Message/External-body; access-type="mail-server"; server="mail-server(a)nisc.sri.com" Content-Type: text/plain SEND rfc1421.txt - - --OtherAccess Content-Type: Message/External-body; name="rfc1421.txt"; site="nic.ddn.mil"; access-type="anon-ftp"; directory="rfc" Content-Type: text/plain - - --OtherAccess-- - - --NextPart-- - ------- End of Forwarded Message -----END PRIVACY-ENHANCED MESSAGE-----

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Re: CELP speech compression code at cygnus.com:/pub/celp.speech.tar.Z
by wcs＠anchor.ho.att.com 10 Feb '93

10 Feb '93

Forwarded for Bill Stewart, who I assume wanted it posted. Eric ----------------------------------------------------------------------------- John, Perry, and others have been commenting on the use of CELP voice compression and crypto with V.32 or better modems to give end-to-end encrypted speech. Perry says: > Fast enough software compression of voice would mean any PC > with a DSP card and a V.32 modem could become an unbreakable scrambler. > The chief problem is that the DSP needed to do decent compression is > very crunchy, and encryption also tends to be crunchy, so there aren't > typically enough cycles on your average PC. Of course, were someone to > commercially market a board that did all this in hardware... (Please excuse any shameless references to my employer's fine hardware products :-); I do science fiction, er, um, systems engineering, not hardware... and it's been a while since our chip people were in my building.) It may not all be packaged on a single board, but it shouldn't be real tough. PC and Mac Boards with AT&T DSP32C chips were out several years ago, which provided something like 25 MFLOPS, which was more than enough to do voice compression and have leftover guts for crypto (or use your 386; DES at 9600 baud shouldn't cause much heartburn.) I assume that by now there are reasonably-priced floating-point DSP boards from several different vendors out, and AT&T makes modem chipsets and supporting A/D and fixed-point DSP integer-crunchers. If CELP can be done in integers, I'd guess you could chain together a couple DSPs and put together a board for ~$100-150 parts-cost. Also, how much can you do with the various SoundBlaster-related boards? Bill

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Re: Compressed/Encrypted Voice using Modems
by pmetzger＠shearson.com 09 Feb '93

09 Feb '93

> From: Eric Hughes <hughes(a)soda.berkeley.edu> > > >By the way, just to bring this back to crypto, everyone should be aware > >that not only did Claude Shannon establish modern information theory, > >he also wrote a seminal paper that established much of modern cryptography. > > Not only that, he was single handedly responsible for the 15 minute > delay rule in reporting stock market transactions. Evidently he > applied information-theoretic techniques to the data and was able to > make a load of money at it. I have no references on this, and would > love to see some. I don't believe this. You can buy data feeds that give you instant market data, rather than 15 minute delayed information. I've worked for operations like Morgan Stanley's Analytic Proprietary Trading Group, and although I've seen some neat tricks applied to market data, I've never heard tell of Shannon developing any, nor is there any delay in the data such groups use for trading. Perry

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PGP key by finger
by Douglas Sinclair 09 Feb '93

09 Feb '93

To all those that asked - my PGP 2.1 key is now available for finger. I appologize to all for the technical difficulties. -- Vercotti: I was terrified of him. Everyone was terrified of Doug. I've seen grown men pull their own heads off rather than see Doug. Even Dinsdale was frightened of Doug. Interviewer: What did he do? Vercotti: He used sarcasm. He knew all the tricks, dramatic irony, metaphor, bathos, puns, parody, litotes and satire. -- Monty Python, Episode 14 PGP 2.1 Key by finger

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February 13 meeting
by Eric Hughes 09 Feb '93

09 Feb '93

Cypherpunks physical meeting Noon sharp, Saturday, February 13, 1993 Cygnus Support Offices, Mt. View, California, USA I apologize for not getting out an announcement for the the last meeting. It showed, both in attendance and organization. My regrets. I make a solemn promise to be there before 12:00 p.m. Let's start on time for a change. I hear that photographers are going to be there, so if you don't want to be photographed, bring your favorite mask. They're nice photographers and they'll ask your permission first so that you don't have to wear your mask at all times. Eric ----------------------------------------------------------------------------- AGENDA ====== -- The Ultra random number generator. I presume Scott Collins is going to talk on this, since he mentioned this, but I have not heard from him. (Hint, hint) Ultra is a new random number generator designed by some statisticians. It allegedly has extremely long period, good distribution properties, and a fast implementation, since it is based on the borrow from a subtract operation. -- Eric Messick will present his posting on envelopes. If any of you need another copy of this, the address of his that I remember is eric(a)toad.com. -- Arthur Abraham will present on hash functions. The talk will include discussion of generally desirable properties and some specific algorithms. -- Some people wanted to talk about the Sidelnikov comments on PGP, but I don't have a presenter yet. -- And the usual progress reports and chat. ----------------------------------------------------------------------------- DIRECTIONS ========== Cygnus Support 1937 Landings Drive Mt. View, CA 94043 +1 415 903 1400 switchboard +1 415 903 1418 John Gilmore Take US 101 toward Mt. View. From San Francisco, it's about a 40-minute drive. Get off at the Rengstorff Ave/Amphitheatre Parkway exit. If you were heading south on 101, you curve around to the right, cross over the freeway, and get to a stoplight. If you were heading north on 101, you just come right off the exit to the stoplight. The light is the intersection of Amphitheatre and Charleston Rd. Take a right on Charleston; there's a right-turn-only lane. Follow Charleston for a short distance. You'll pass the Metaphor/Kaleida buildings on the right. At a clump of palm trees and a "Landmark Deli" sign, take a right into Landings Drive. At the end of the road, turn left into the complex with the big concrete "Landmark" sign. Follow the road past the deli til you are in front of the clock tower that rises out of one of the buildings, facing you. Enter through the doors immediately under the clock tower. They'll be open between noon and 1PM at least. (See below if you're late.) Once inside, take the stairs up, immediately to your right. At the top of the stairs, turn right past the treetops, and we'll be in 1937 on your left. The door is marked "Cygnus". If you are late and the door under the clock tower is locked, you can walk to the deli (which will be around the building on your left, as you face the door). Go through the gate in the fence to the right of the deli, and into the back lawns between the complex and the farm behind it. Walk forward and right around the buildings until you see a satellite dish in the lawn. Go up the stairs next to the dish, which are the back stairs into the Cygnus office space. We'll prop the door (or you can bang on it if we forget). Or, you can find the guard who's wandering around the complex, who knows there's a meeting happening and will let you in. They can be beeped at 965 5250, though you'll have trouble finding a phone. Don't forget to eat first, or bring food at noon! I recommend hitting the burrito place on Rengstorff (La Costen~a) at about 11:45. To get there, when you get off 101, take Rengstorff (toward the hills) rather than Amphitheatre (toward the bay). Follow it about ten blocks until the major intersection at Middlefield Road. La Costen~a is the store on your left at the corner. You can turn left into the narrow lane behind the store, which leads to a parking lot, and enter by the front door, which faces the intersection. To get to the meeting from there, just retrace your route on Rengstorff, go straight over the freeway, and turn right at the stoplight onto Charleston; see above. See you there! John Gilmore

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

09 Feb '93

> > haven't seen it. > OK, fearing the worst (maybe I forgot to CC my message to cypherpunks, but I'm sure I did), I'll repost my original message. It was a God-sent that I got cut off last night while composing it, and expreserve preserved it. Here it is: > > > ... because in FSK systems which code 1 bit per symbol > > (only two phases), bps = baud. But then and ONLY then.... > > Uhh, don't you mean two frequencies? FSK is Frequency Shift Key, not > Phase Shift Key (PSK).. ;-) > > Actually, I KNOW you meant this, and it was probably just a typo, > right? > > -derek > Woops! Sorry. To compensate, I'll give more information. In the Bell 103 system (FSK), the frequencies are 2125Hz for answer, and 1170Hz for originate carriers, with the frequency shifts being +/- 100Hz. Compare with CCITT's V.21, and substitute the carrier frequencies with 1750 and 1080Hz. Same +/- 100Hz shifting. Someone else mentioned the almighty Claude Shannon in another message concern- ing maximum bit-rate of a voice channel, and I wanted to clear up what was said. Shannon's capacity formula said capacity in bits-per-second equals bandwidth of channel in hertz times the base-2 (binary) logarithm of one plus the signal (in watts) to noise (in watts) ratio. As a side note, I say watts because commonly, today, you measure signal and noise levels in decibels (dB), and the S/N ratio is in dBm's (decibels per milliwatt). In the phone system, we say a voice frequency channel (VFC) has a bandwidth of 4kHz. In-band signalling is approximately from .3 to 3kHz. This formula (yielding the Shannon limit) is based on a "Gaussian Band Limited Channel" (GBLC), which is an approximation of a VFC, with a signal wave of S watts at the input of an "ideal" low-pass filter, subjected to Gaussian noise with a mean power of N watts (uniformly). Written, it's C = W log2(1 + S/N). A simple example you can do in your head is W=3000Hz, pick an S/N of 1023, 1+1023 is 1024, and base-2 log of 1024 is simply 10, 3000 * 10 is 30000, so Shannon's limit for these values is C = 30000bps. Play with it. Bear in mind, Shannon didn't consider intersymbol interference. Nyquist did. Compare this to Harry Nyquist's 2-bit rule, 2W, or double the bandwidth, and get the maximum bit rate (this line of thinking led him to the infamous Nyquist sampling theorem, sample at a rate twice the bandwidth of a channel, and you have all the information you need to reconstruct it at the receiving end). But Nyquist deals only with binary systems. Shannon's formula shows that theoretically you could increase the data rate indefinitely by increasing the S/N ratio. We achieve this in modern modulation systems by using multilevel systems, (M-ary for short, with M > 2), and hence the protocols I described in my previous message. We can apply Nyquist's 2-bit rule to the multilevel system by saying 2W log2 M bps is achievable, with an acceptable error rate. As we increase M (number of bits per symbol), so we have to find ways to increase the signal to noise ratio, to maintain an acceptable error rate. The whole thing is stupendously interesting to me, as I hope it is to the rest of you folks. To blow your mind with sheer genius, read Shannon's classic "A Mathematical Theory of Communication" in Bell System Tech Journal, July and October of '48 at your local university. Also Nyquist's "Certain Topics in Telegraph Transmission Theory", April '28. Know your roots. Good night.

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