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    • Favorite 13 March 2019
      bobjonkman favorited something by lnxw48a1: You go to post, you look it over. It looks okay. Hit "Post" and now there are words missing, words spelled incorrectly, punctuation missing.
    • bobjonkman repeated a notice by lnxw48a1 13 March 2019
      RT @lnxw48a1 You go to post, you look it over. It looks okay. Hit "Post" and now there are words missing, words spelled incorrectly, punctuation missing.
    • New note by bobjonkman 7 March 2019
      If you have an external clock that's transmitted exclusively over an analogue channel, then everyone would hear the beats at the same time (barring speed-of-light transmission times, which is really only a factor if the transmission uses geosynchronous satellites). But if there is any digital transmission then you're back to the same problem. Not everyone […]
    • bobjonkman repeated a notice by lauraritchie 7 March 2019
      RT @lauraritchie @bobjonkman @strangeattractor what if they instead of playing reactively everyone played to a world clock? - people could always record their contributions and video magic can be done with screens in a room and then the one room is streamed.
    • New note by bobjonkman 4 March 2019
      The solution would be to have an analogue connection from end-to-end. But today, even analogue phones are connected to digital switching networks, so you can't even use ordinary landline phones and expect to get no delay. You can get "leased lines" from the phone companies that are analogue end-to-end, but leasing a tuned circuit that […]
    • New note by bobjonkman 4 March 2019
      Performing music together over an Internet connection is next to impossible if there is *any* lag at all. Typically, the lag is caused by short 10-50 millisecond delays for every router hop, at minimum one hop from you to your ISP, another from ISP to Internet Exchange Point (IXP), IXP to my ISP, and a […]
    • bobjonkman repeated a notice by lauraritchie 4 March 2019
      RT @lauraritchie More on the livestreaming dilemma...I need to have the option of multiple participants AT THE SAME TIME - like playing in a band. So maybe the keyboard and drums are in one place (live) and the sax player joins from another country via a link. Does anyone know of a platform that lets […]
    • New note by bobjonkman 3 March 2019
      The duct tape is in very good condition.
    • New note by bobjonkman 3 March 2019
      Test receive, also pls ignore
    • New note by bobjonkman 25 February 2019
      ...and wouldn't you have to include the time to insert 225,000 microSD cards in your laptop, write 256 GBytes to them, and then (after transporting them at about 10 PBytes/second, assuming 6 seconds of flight time), spend more time to insert those 225,000 microSD cards in the other guy's laptop to read those 256 GBytes? […]

Archive for March, 2014

The cost of long GnuPG/PGP keys

Posted by Bob Jonkman on 25th March 2014

Never Eat That Green Food At The Back Of The Fridge

Never Trust Anyone Over Thirty

and

Never Sign A GnuPG/PGP Key That’s Older Than You Are

Face peeking into fridge

Looking for green food at the back of the fridge

OK, only one of those is true, and it’s not the last one. At the University of Waterloo Keysigning Party last fall, some of the people signing my key were younger than the key they were signing!

At the keysigning I was having a discussion with someone about key lengths. In particular, choosing 4096 bits instead of 2048. I was reading that GnuPG has a limit of 4096 bits, but that 4096 should be enough for all time to come.

I’ve read online that GnuPG does actually support larger key sizes but that there is a const in the source code limiting it to 4096. The reasons for doing so are supposedly speed, 4096 would be very slow to generate and use, and comparability with other implementations that may not support larger keys. Personally I think it’s an inevitability that this will be increased in time but we’re not there yet.

In 1996 when I started with PGP a 1024 bit key was considered adequate, by 1999 a 2048 bit key was still considered large.

Consider Moore’s Law: every 18 months computing capacity doubles and costs halve. I’m not sure if that means that over 18 months x flops increases to 2x flops at the same price, or that in 18 months the cost of x flops is half of today’s cost, or if it means that in 18 months the cost of 2x flops will be half the cost of x flops today. If the latter, then today’s x flops/$ is x/4 flops/$ in 18 months. That factor of four is an increase of two bits every 18 months, or four bits every 3 years.

So, the cost in 1996 to brute-force crack a 1024 bit key is the same as the cost in 1999 to crack a 1028 bit key. And in 2014, 18 years later, it’s the same cost as cracking a 1048 bit key (an additional 24 bits).

An increase in key size from 1024 bits to 2048 bits buys an additional 768 years of Moore’s Law. And going from 2048 bits to 4096 bits buys an additional 1536 years of Moore’s Law.

Is Moore’s Law overestimating the cost of cracking keys? Are there fundamental advances in math that have dropped the cost of cracking 1024 bit keys to near-zero? What’s the economic justification for crippling keysizes in GnuPG, anyway?

–Bob, who is not trolling but really wants to know.

Day 57 / 365 – refrigerator by Jason Rogers is used under a CC BYCC BY license.

This post is based on a message to the KWCrypto Mailing List.

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