2016-12-04_-_hello_human

anonymous@undisclosed.example.com (Anonymous) — Tue, 15 Jun 2021 20:09:22 +0000

2016-12-04 - hello human

few days ago we had an open-hours in our SW-dev department. since we mostly do algorithmic data processing, embedded system… and do not have hardware platform on-site… it's really hard to show it in an interesting fashion, for non-technical ppl. i've decided to show something connected to a SW development in general, but not directly tided to our system. it was inspired by a though that “SW dev is about putting a spirit (ghost?) into a machine”. :)

i though – how about a simple project with a camera, to catch and track faces, using servo motors? when some1 approach it, system catches a focus and move along a person's face movements, to keep her at focus?

…and so – during a course of 3 evenings hello human project was brought from a rough idea to a real life machine. :)

project is interesting since, because though it contains software, electronics and 3d-printed model… it was almost solely about programming! just think:

main logic was implemented in python
image processing is done with OpenCV (i.e. C)
servo motors controller is implemented in C++
all the 3d-printer are programmed in OpenSCAD
PCB is done in Eagle

the only thing on the list, that is not about programming is PCB-design SW. all the rest is pure programming. now isn't that cute? :)

it turned out that it drawn quite a bit of attention. ppl asked about how it works, how much would it cost to build such a thing at home (btw: there's actually only about 30EUR worth of parts in it!)… and there was quite some laughter, when vision system decided that cat drawing on one of the girls' dress is actually a face, and followed it for a long time! ;)

some practical applications? well – aside from keeping ppl interested in SW development and modern technologies… not that many. ;) it could be used for monitoring, video conferencing (ever got annoyed about camera not following your movements in the room, while chatting?)… or an extended version, that would detect/monitor who's speaking, and focus on that person (useful for video-conferencing, when there are many ppl in the room). who knows – maybe one day, when i'll get bored with whatever i'm doing at that particular moment? ;)

2016-12-04_-_multi-disk_encryption

anonymous@undisclosed.example.com (Anonymous) — Tue, 15 Jun 2021 20:09:22 +0000

2016-12-04 - multi-disk encryption

some time ago i had an issue – i started to use (RAIDed) SSD disks for main system and (also RAIDed) HDD disks for storage of larger pieces of data. of course both encrypted. and that's the tricky place – entering password for both disks at boot time!

if i already have main disk encrypted, cannot i just read password off it, to automatically decrypt the second one? it turns out you can. :)

dd if=/dev/random of=/path/to/key.bin bs=4096 count=1
cryptsetup luksFormat /dev/my-disk /path/to/key.bin

now the last part is to add a proper entry to crypttab, so that disk automatically gets decrypted during boot (shortly after “/” gets decrypted). add entry like this, to the /etc/crypttab file:

my_crypt_dev_2 UUID=xxx-xxx-xxx-xxxx /path/to/key.bin luks

you can check UUID for oyur disks, by checking out links in udev:

ls -l /dev/disk/by-uuid/

note that eve though you can now automatically decrypt 2nd disk with off-disk password file, it's still good idea to assign password to it (eg. in case you loose access to the password-file). fortunately LUKS offers multiple passwords out of the box, so this is not a problem. :)

cryptsetup luksAddKey --key-file /path/to/key.bin /dev/my-disk

happy encrypting! :)

BaSzErr - blog:2016:12:04

2016-12-04_-_hello_human

2016-12-04 - hello human

2016-12-04_-_multi-disk_encryption

2016-12-04 - multi-disk encryption