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    • New note by bobjonkman 14 January 2023
      I seem to recall there's a standard API that should be common to all the #StatusNet derivitave servers. I'm pretty sure that in its infancy Mastodon conformed to that API. But Mastodon's API expanded beyond that, and I suspect some of the common API was removed, probably around the time #OStatus was dropped from Mastodon […]
    • New note by bobjonkman 14 January 2023
      Twidere has stopped working for Twitter accounts. My Mastodon account still works nicely. I thought maybe the Twidere API keys for the developer had been revoked, or that something had gone wrong with my phone (It's a vanilla Samsung with Android 12, but I've refused to install any of the Samsung or Google apps). I […]
    • bobjonkman repeated a notice by heluecht 14 January 2023
      RT @heluecht !Friendica Admins As you might have heard, there are issues with the Twitter API. Several favourite clients stopped working, while others (still) do. By now there hadn't been any word if there is some massive Problem or if this was some deliberate action. Whatever is causing these issues, at least my connection still […]
    • Favorite 5 January 2023
      bobjonkman favorited something by lnxw48a1: https://imaginary.ca/blog/2017/06/16/top-hat/#more-231 [imaginary ca] I am glad this instructor thinks this way. Too many don't seem to care how badly a vendor's product affects students.
    • Favorite 5 January 2023
      bobjonkman favorited something by lnxw48a1: https://500ish.com/mastodon-brought-a-protocol-to-a-product-fight-ba9fda767c6a #Medium link; don't be surprised if it does weird things before showing you the article. "Mastodon brought a protocol to a product fight" > Yes, yes, the network is under immense strain as people flee the Elon strain infecting Twitter. But come on, there are folks who really believe […]
    • bobjonkman repeated a notice by lnxw48a1 5 January 2023
      RT @lnxw48a1 https://500ish.com/mastodon-brought-a-protocol-to-a-product-fight-ba9fda767c6a #Medium link; don't be surprised if it does weird things before showing you the article. "Mastodon brought a protocol to a product fight" > Yes, yes, the network is under immense strain as people flee the Elon strain infecting Twitter. But come on, there are folks who really believe this is going […]
    • Favorite 5 January 2023
      bobjonkman favorited something by lnxw48a1: > For now, I’ll just say that while I fully understand why everyone wants Mastodon to be the new Twitter. Or the better Twitter. The more ideal Twitter. Or whatever. It’s just not going to happen. Mastodon brought a protocol to a product fight. Maybe Ivory or another client can […]
    • bobjonkman repeated a notice by clacke 4 January 2023
      RT @clacke NZ PM Jacinda Ardern called ACT leader David Seymour a prick on a hot mike in parliament. She apologized, he accepted, they had a laugh, and now together they've framed and signed a transcript of the exchange, selling it to the highest bidder, currently at 100 kNZD. The proceeds will go prostate cancer […]
    • Favorite 4 January 2023
      bobjonkman favorited something by clacke: NZ PM Jacinda Ardern called ACT leader David Seymour a prick on a hot mike in parliament.She apologized, he accepted, they had a laugh, and now together they've framed and signed a transcript of the exchange, selling it to the highest bidder, currently at 100 kNZD. The proceeds will go […]
    • New comment by bobjonkman 14 December 2022
      @lnxw48a1 "Pop" is also the Canadian word for carbonated soft drinks...

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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