+* bkgpslog task list
+** DONE Add job control for short buffer length
+ CLOSED: [2020-07-02 Thu 16:04]
+2020-07-02T14:56Z; bktei> File write operations were bundled into a
+magicWriteBuffer function that is called then detached from the script
+shell (job control), but the detached job is not tracked by the main
+script. A problem may arise if two instances of magicWriteBuffer
+attempt to write to the same tar simultaneously. Two instances of
+magicWriteBuffer may exist if the buffer length is low (ex: 1 second);
+the default buffer length of 60 seconds should reduce the probability
+of a collision but it should be possible for the main script to track
+the process ID of a magicWriteBuffer() as soon as it detaches and then
+checking (via ~$!~ as described [[https://bashitout.com/2013/05/18/Ampersands-on-the-command-line.html][here]]) that the process is still alive.
+2020-07-02T15:23Z; bktei> I found that the Bash ~wait~ built-in can be
+used to delay processing until a specified job completes. The ~wait~
+command will pause script execution until all backgrounded processes
+complete.
+2020-07-02T16:03Z; bktei> Added ~wait~.
+** DONE Rewrite tar initialization function
+ CLOSED: [2020-07-02 Thu 17:23]
+2020-07-02T17:23Z; bktei> Simplify tar initialization function so
+VERSION file is used to test appendability of tar as well as to mark
+when a new session is started.
+** DONE Consolidate tar checking/creation into function
+ CLOSED: [2020-07-02 Thu 18:33]
+2020-07-02T18:33Z; bktei> Simplify how the output tar file's existence
+is checked and its status as a valid tar file is validated. This was
+done using a new function ~checkMakeTar~.
+** DONE Add VERSION if output tar deleted between writes
+
+ CLOSED: [2020-07-02 Thu 20:22]
+2020-07-02T20:21Z; bktei> Added bkgpslog-specified function
+magicWriteVersion() to be called whenever a new time-stamped ~VERSION~
+file needs to be generated and appended to the output tar file
+~PATHOUT_TAR~.
+** DONE Rewrite buffer loop to reduce lag between gpspipe runs
+
+ CLOSED: [2020-07-03 Fri 20:57]
+2020-07-03T17:10Z; bktei> As is, there is still a 5-6 second lag
+between when ~gpspipe~ times out at the end of a buffer round and when
+~gpspipe~ is called by the subsequent buffer round. I believe this can
+be reduced by moving variable manipulations inside the
+asynchronously-executed magicWriteBuffer() function. Ideally, the
+while loop should look like:
+
+#+BEGIN_EXAMPLE
+while( $SECONDS < $SCRIPT_TTL); do
+ gpspipe-r > "$DIR_TMP"/buffer.nmea
+ writeBuffer &
+done
+#+END_EXAMPLE
+2020-07-03T20:56Z; bktei> I simplified it futher to something like
+this:
+#+BEGIN_EXAMPLE
+while( $SECONDS < $SCRIPT_TTL); do
+ writeBuffer &
+ sleep $SCRIPT_TTL
+done
+#+END_EXAMPLE
+
+Raspberry Pi Zero W shows approximately 71ms of drift per buffer round
+with 10s buffer.
+** TODO Feature: Recipient watch folder
+2020-07-03T21:28Z; bktei> This feature would be to scan the contents
+of a specified directory at the start of every buffer round in order
+to determine encryption (age) recipients. This would allow a device to
+dynamically encrypt location data in response to automated changes
+made by other tools. For example, if such a directory were
+synchronized via Syncthing and changes to such a directory were
+managed by a trusted remote server, then that server could respond to
+human requests to secure location data.
+
+Two specific privacy subfeatures come to mind:
+
+1. Parallel encryption: Given a set of ~n~ public keys, encrypt data
+ with a single ~age~ command with options causing all ~n~ pubkeys to
+ be recipients. In order to decrypt the data, any individual private
+ key could be used. No coordination between key owners would be
+ required to decrypt.
+
+2. Sequential encryption: Given a set of ~n~ public keys, encrypt data
+ with ~n~ sequential ~age~ commands all piped in series with each
+ ~age~ command utilizing only one of the ~n~ public keys. In order
+ to decrypt the data, all ~n~ private keys would be required to
+ decrypt the data. Since coordination is required, it is less
+ convenient than parallel encryption.
+
+In either case, a directory would be useful for holding configuration
+files specifying how to execute which or combination of which features
+at the start of every buffer round.
+
+I don't yet know how to program the rules, although I think it'd be
+easier to simply add an option providing ~bkgpslog~ with a directory
+to watch. When examining the directory, check for a file with the
+appropriate file extension (ex: .pubkey) and then read the first line
+into the script's pubKey array.
+
+** TODO Feature: Simplify option to reduce output size
+
+~gpsbabel~ [[https://www.gpsbabel.org/htmldoc-development/filter_simplify.html][features]] a ~simplify~ option to trim data points from GPS
+data. There are several methods for prioritizing which points to keep
+and which to trim, although the following seems useful given some
+sample data I've recorded in a test run of ninfacyzga-01:
+
+#+BEGIN_EXAMPLE
+gpsbabel -i nmea -f all.nmea -x simplify,error=10,relative -o gpx \
+-F all-simp-rel-10.gpx
+#+END_EXAMPLE
+
+An error level of "10" with the "relative" option seems to retain all
+desireable features for GPS data while reducing the number of points
+along straightaways. File size is reduced by a factor of
+about 11. Noise from local stay-in-place drift isn't removed; a
+relative error of about 1000 is required to remove stay-in-place drift
+noise but this also trims all but 100m-size features of the recorded
+path. A relative error of 1000 reduces file size by a factor of
+about 450.
+
+#+BEGIN_EXAMPLE
+ 67M relerror-0.001.kml
+ 66M relerror-0.01.kml
+ 58M relerror-0.1.kml
+ 21M relerror-1.kml
+5.8M relerror-10.kml
+797K relerror-100.kml
+152K relerror-1000.kml
+#+END_EXAMPLE
+
+** TODO Feature: Generalize bkgpslog to bklog function
+2020-07-05T02:42Z; bktei> Transform ~bkgpslog~ into a modular
+component called ~bklog~ such that it processes a stdout stream of any
+external command, not just ~gpspipe -r~. This would permit reuse of
+the ~bkgpslog~ code for logging not just GPS data but things like
+pressure, temperature, system statistics, etc.
+2020-07-05T16:35Z; bktei>
+: bklog -r age1asdf -o log.tar # encrypt/compress stdin to log.tar
+: bklog -x -f log.tar -i age.key -O /tmp # extract and decrypt
+
+Making ~bklog~ follow the [[https://en.wikipedia.org/wiki/Unix_philosophy][Unix philosophy]] means that it shouldn't care
+what kind of text is fed to it.
+
+*** ~bklog~ Design vs. Unix Philosophy
+**** Pubkey dir watching
+The feature of periodically checking a directory for changes in the
+pubkeys it contains should be justified by its usefulness; if the
+complexity cannot be justified then the feature should be removed.
+**** Defaults vs options
+Many options can cause the tool to become complex in unjustifiable
+ways. Currently I am adding options because I want the ability to
+modify the script's behavior without having to modify the source code
+on the machine in which the code is running. I should consider
+removing features at some point and having the program force defaults
+on the user. For example, allowing the specification of a temporary
+directory, while useful for me, is probably not useful for most people
+who don't know or care about the difference between ~/tmp~ and
+~/dev/shm~.
+**** Script time to live (TTL)
+I initially implemented a script time-to-live feature because I was
+unsure in my ability to program script that could run for long periods
+of time without causing a runaway usage of memory. I still think it's
+a good idea to offer a script TTL option to the user but I think the
+default should be to simply run forver.
+** TODO: Evaluate ~rsyslog~ as stand-in for this work
+2020-07-05T02:57Z; bktei> I searched for "debian iot logging" ("iot"
+as in "Internet of Things", the current buzzword for small low-power
+computers being used to provide microservices for owners in their own
+home) and came across several search results mentioning ~syslog~ and
+~rsyslog~.
+
+https://www.thissmarthouse.net/consolidating-iot-logs-into-mysql-using-rsyslog/
+https://rsyslog.readthedocs.io/en/latest/tutorials/tls.html
+https://serverfault.com/questions/20840/how-would-you-send-syslog-securely-over-the-public-internet
+https://www.rsyslog.com/
+
+My impression is that ~rsyslog~ is a complex software package designed
+to offer many features, some of which possibly might satisfy my
+needs.
+
+However, as stated in the repository README, the objective of the
+~ninfacyzga-01~ project is "Observing facts of the new". This means
+that the goal is not only to record location data but any data that
+can be captured by a sensor. This means the capture of the following
+environmental phenomena are within the scope of this device:
+
+*** Sounds (microphone)
+*** Light (camera)
+*** Temperature (thermocouple)
+*** Air Pressure (barometer)
+*** Acceleration Vector (acceleromter / gyroscope)
+*** Magnetic Field Vector (magnetometer)
+
+This brings up the issue of respecting privacy of others in shared
+spaces through which ~ninfacyzga-01~ may pass through. ~ninfacyzga-01~
+should encrypt data it records according to rules set by its
+owner.
+
+One permissive rule could be that if ~ninfacyzga-01~ detects that a
+person (let's call her Alice) enters a room, it should add Alice's
+encryption public key to the list of recipients against which it
+encrypts data without Alice having to know how ~ninfacyzga-01~ is
+programmed (she might have a ~calkuptcana~ agent on her person that
+broadcasts her privacy preferences). Meanwhile, ~ninfacyzga-01~ may
+publish its observations to a repository that Alice and other members
+of the shared communal space have access to (ex: a read-only shared
+directory on a local network WiFi). Alice could download all the files
+in the shared repository but she would only be able to decrypt files
+generated when she was physically near enough to ~ninfacyzga-01~ for
+it to detect that her presence was within some spatial boundary.
+
+A more restrictive rule could resemble the permissive rule in that
+~ninfacyzga-01~ uses Alice's encryption public key only when she is
+physically near by, except that it encrypts logged files against
+public keys in a sequential manner. This would mean that all people
+who were near ~ninfacyzga-01~ would have to pass around each log file
+to eachother so that they could decrypt the content.
+
+That said, according to [[https://www.rsyslog.com/doc/master/tutorials/database.html][this ~rsyslog~ page]], ~rsyslog~ is more a data
+wrangling system for collecting data from disparate sources of
+different types and outputting data to text files on disk than a
+system committed to the server-client model of database storage. So, I
+think converting ~bkgpslog~ into a ~bklog~ script that appends
+encrypted and compressed data to a tar file for later extraction
+(possibly the same script with future features) would be best.
+
+** TODO: Place persistent recip. updates in asynchronous coproc
+2020-07-06T19:37Z; bktei> In order to update the recipient list, the
+magicParseRecipientDir() function needs to be run each buffer period
+in order to scan for changes in the recipient list. However, such a
+scan takes time; if the magicGatherWriteBuffer() function must pause
+until magicParseRecipientDir() completes, then a significant pause
+between buffer sessions may occur, causing detectable gaps in location
+data between buffer rounds.
+
+I looked for ways in which I might start magicParseRecipientDir()
+asynchronously immediately before running the data collection command
+and then collect its output at the start of the next buffer round. One
+way using the ~coproc~ Bash built-in is described [[https://stackoverflow.com/a/20018504/10850071][here]]. I'd have to
+make the asynchronous function output the recipient list to stdout
+which would then be ~read~ into the ~recPubKeysValid~ array in the
+main loop. However, for now, I'm putting the magicParseRecipientDir()
+as-is in the main loop and accepting the delay for now.
projects / EVA-2020-02.git / blobdiff