- <div class="title"><a href="http://people.skolelinux.org/pere/blog/The_life_and_death_of_a_laptop_battery.html">The life and death of a laptop battery</a></div>
- <div class="date">24th September 2015</div>
- <div class="body"><p>When I get a new laptop, the battery life time at the start is OK.
-But this do not last. The last few laptops gave me a feeling that
-within a year, the life time is just a fraction of what it used to be,
-and it slowly become painful to use the laptop without power connected
-all the time. Because of this, when I got a new Thinkpad X230 laptop
-about two years ago, I decided to monitor its battery state to have
-more hard facts when the battery started to fail.</p>
-
-<img src="http://people.skolelinux.org/pere/blog/images/2015-09-24-laptop-battery-graph.png"/>
-
-<p>First I tried to find a sensible Debian package to record the
-battery status, assuming that this must be a problem already handled
-by someone else. I found
-<a href="https://tracker.debian.org/pkg/battery-stats">battery-stats</a>,
-which collects statistics from the battery, but it was completely
-broken. I sent a few suggestions to the maintainer, but decided to
-write my own collector as a shell script while I waited for feedback
-from him. Via
-<a href="http://www.ifweassume.com/2013/08/the-de-evolution-of-my-laptop-battery.html">a
-blog post about the battery development on a MacBook Air</a> I also
-discovered
-<a href="https://github.com/jradavenport/batlog.git">batlog</a>, not
-available in Debian.</p>
-
-<p>I started my collector 2013-07-15, and it has been collecting
-battery stats ever since. Now my
-/var/log/hjemmenett-battery-status.log file contain around 115,000
-measurements, from the time the battery was working great until now,
-when it is unable to charge above 7% of original capacity. My
-collector shell script is quite simple and look like this:</p>
-
-<pre>
-#!/bin/sh
-# Inspired by
-# http://www.ifweassume.com/2013/08/the-de-evolution-of-my-laptop-battery.html
-# See also
-# http://blog.sleeplessbeastie.eu/2013/01/02/debian-how-to-monitor-battery-capacity/
-logfile=/var/log/hjemmenett-battery-status.log
-
-files="manufacturer model_name technology serial_number \
- energy_full energy_full_design energy_now cycle_count status"
-
-if [ ! -e "$logfile" ] ; then
- (
- printf "timestamp,"
- for f in $files; do
- printf "%s," $f
- done
- echo
- ) > "$logfile"
-fi
-
-log_battery() {
- # Print complete message in one echo call, to avoid race condition
- # when several log processes run in parallel.
- msg=$(printf "%s," $(date +%s); \
- for f in $files; do \
- printf "%s," $(cat $f); \
- done)
- echo "$msg"
-}
-
-cd /sys/class/power_supply
-
-for bat in BAT*; do
- (cd $bat && log_battery >> "$logfile")
-done
-</pre>
-
-<p>The script is called when the power management system detect a
-change in the power status (power plug in or out), and when going into
-and out of hibernation and suspend. In addition, it collect a value
-every 10 minutes. This make it possible for me know when the battery
-is discharging, charging and how the maximum charge change over time.
-The code for the Debian package
-<a href="https://github.com/petterreinholdtsen/battery-status">is now
-available on github</a>.</p>
-
-<p>The collected log file look like this:</p>
-
-<pre>
-timestamp,manufacturer,model_name,technology,serial_number,energy_full,energy_full_design,energy_now,cycle_count,status,
-1376591133,LGC,45N1025,Li-ion,974,62800000,62160000,39050000,0,Discharging,
-[...]
-1443090528,LGC,45N1025,Li-ion,974,4900000,62160000,4900000,0,Full,
-1443090601,LGC,45N1025,Li-ion,974,4900000,62160000,4900000,0,Full,
-</pre>
-
-<p>I wrote a small script to create a graph of the charge development
-over time. This graph depicted above show the slow death of my laptop
-battery.</p>
-
-<p>But why is this happening? Why are my laptop batteries always
-dying in a year or two, while the batteries of space probes and
-satellites keep working year after year. If we are to believe
-<a href="http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries">Battery
-University</a>, the cause is me charging the battery whenever I have a
-chance, and the fix is to not charge the Lithium-ion batteries to 100%
-all the time, but to stay below 90% of full charge most of the time.
-I've been told that the Tesla electric cars
-<a href="http://my.teslamotors.com/de_CH/forum/forums/battery-charge-limit">limit
-the charge of their batteries to 80%</a>, with the option to charge to
-100% when preparing for a longer trip (not that I would want a car
-like Tesla where rights to privacy is abandoned, but that is another
-story), which I guess is the option we should have for laptops on
-Linux too.</p>
-
-<p>Is there a good and generic way with Linux to tell the battery to
-stop charging at 80%, unless requested to charge to 100% once in
-preparation for a longer trip? I found
-<a href="http://askubuntu.com/questions/34452/how-can-i-limit-battery-charging-to-80-capacity">one
-recipe on askubuntu for Ubuntu to limit charging on Thinkpad to
-80%</a>, but could not get it to work (kernel module refused to
-load).</p>
-
-<p>I wonder why the battery capacity was reported to be more than 100%
-at the start. I also wonder why the "full capacity" increases some
-times, and if it is possible to repeat the process to get the battery
-back to design capacity. And I wonder if the discharge and charge
-speed change over time, or if this stay the same. I did not yet try
-to write a tool to calculate the derivative values of the battery
-level, but suspect some interesting insights might be learned from
-those.</p>
-
-<p>Update 2015-09-24: I got a tip to install the packages
-acpi-call-dkms and tlp (unfortunately missing in Debian stable)
-packages instead of the tp-smapi-dkms package I had tried to use
-initially, and use 'tlp setcharge 40 80' to change when charging start
-and stop. I've done so now, but expect my existing battery is toast
-and need to be replaced. The proposal is unfortunately Thinkpad
-specific.</p>
+ <div class="title"><a href="http://people.skolelinux.org/pere/blog/Idea_for_storing_trusted_timestamps_in_a_Noark_5_archive.html">Idea for storing trusted timestamps in a Noark 5 archive</a></div>
+ <div class="date"> 7th June 2017</div>
+ <div class="body"><p><em>This is a copy of
+<a href="https://lists.nuug.no/pipermail/nikita-noark/2017-June/000297.html">an
+email I posted to the nikita-noark mailing list</a>. Please follow up
+there if you would like to discuss this topic. The background is that
+we are making a free software archive system based on the Norwegian
+<a href="https://www.arkivverket.no/forvaltning-og-utvikling/regelverk-og-standarder/noark-standarden">Noark
+5 standard</a> for government archives.</em></p>
+
+<p>I've been wondering a bit lately how trusted timestamps could be
+stored in Noark 5.
+<a href="https://en.wikipedia.org/wiki/Trusted_timestamping">Trusted
+timestamps</a> can be used to verify that some information
+(document/file/checksum/metadata) have not been changed since a
+specific time in the past. This is useful to verify the integrity of
+the documents in the archive.</p>
+
+<p>Then it occured to me, perhaps the trusted timestamps could be
+stored as dokument variants (ie dokumentobjekt referered to from
+dokumentbeskrivelse) with the filename set to the hash it is
+stamping?</p>
+
+<p>Given a "dokumentbeskrivelse" with an associated "dokumentobjekt",
+a new dokumentobjekt is associated with "dokumentbeskrivelse" with the
+same attributes as the stamped dokumentobjekt except these
+attributes:</p>
+
+<ul>
+
+<li>format -> "RFC3161"
+<li>mimeType -> "application/timestamp-reply"
+<li>formatDetaljer -> "<source URL for timestamp service>"
+<li>filenavn -> "<sjekksum>.tsr"
+
+</ul>
+
+<p>This assume a service following
+<a href="https://tools.ietf.org/html/rfc3161">IETF RFC 3161</a> is
+used, which specifiy the given MIME type for replies and the .tsr file
+ending for the content of such trusted timestamp. As far as I can
+tell from the Noark 5 specifications, it is OK to have several
+variants/renderings of a dokument attached to a given
+dokumentbeskrivelse objekt. It might be stretching it a bit to make
+some of these variants represent crypto-signatures useful for
+verifying the document integrity instead of representing the dokument
+itself.</p>
+
+<p>Using the source of the service in formatDetaljer allow several
+timestamping services to be used. This is useful to spread the risk
+of key compromise over several organisations. It would only be a
+problem to trust the timestamps if all of the organisations are
+compromised.</p>
+
+<p>The following oneliner on Linux can be used to generate the tsr
+file. $input is the path to the file to checksum, and $sha256 is the
+SHA-256 checksum of the file (ie the "<sjekksum>.tsr" value mentioned
+above).</p>
+
+<p><blockquote><pre>
+openssl ts -query -data "$inputfile" -cert -sha256 -no_nonce \
+ | curl -s -H "Content-Type: application/timestamp-query" \
+ --data-binary "@-" http://zeitstempel.dfn.de > $sha256.tsr
+</pre></blockquote></p>
+
+<p>To verify the timestamp, you first need to download the public key
+of the trusted timestamp service, for example using this command:</p>
+
+<p><blockquote><pre>
+wget -O ca-cert.txt \
+ https://pki.pca.dfn.de/global-services-ca/pub/cacert/chain.txt
+</pre></blockquote></p>
+
+<p>Note, the public key should be stored alongside the timestamps in
+the archive to make sure it is also available 100 years from now. It
+is probably a good idea to standardise how and were to store such
+public keys, to make it easier to find for those trying to verify
+documents 100 or 1000 years from now. :)</p>
+
+<p>The verification itself is a simple openssl command:</p>
+
+<p><blockquote><pre>
+openssl ts -verify -data $inputfile -in $sha256.tsr \
+ -CAfile ca-cert.txt -text
+</pre></blockquote></p>
+
+<p>Is there any reason this approach would not work? Is it somehow against
+the Noark 5 specification?</p>
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