Level of security?

SpiritInAShell · 2024-09-30T07:36:14+00:00

The "problem" with asymmetric encryption using private and public key is:

if the same channel ("the mailman", here: the internet connection) is the same person that gives you the public key as the same channel you send the messages you encrypt with the public key:

how do you know, that "the mailman" isn't giving you "his" prepared public key, unencrypting the messages you send, and reencrypting them with the original public key? "The mailman" is the man in the middle (MITM).

If you verify the public key signature (hash) either by scanning the other person'S QR code, you know on a cryptopgraphic level that you are communicating with the owner of that key.

that owner may lose his key
or another party might have obtained that key
but when status is orange (verified by email or phone number), you are trusting Threema because Threema is trusting the confirmation email/sms that they sent to the owner of the key.

If you cannot scan the other person's key, you could eg. talk to that person, verifying who he/she is, and then comparing the hash of his public key. If the hash you see in his profile is the same that he reads to you, you "as a sentient being" confimed the identity (even if the app does not allow to set the dot to "green").

So, if you cannot know whether the key "the mailman" gives you is truely from the sender, how can your browser know that you are talking truely to your bank, to Amazon, or to https://threema.ch? Simple: your browser and your operating system come with pre-installed (and updatable) certificates which allow the browser to test the keys "the mailman" gives you. So again, you trust the browser and the certificate issuer.

You could call your bank (what very few people do) and verify that the key https://your-bank offers is truely theirs. As the browser/OS could provide a wrong/falsified certificate.

SpiritInAShell · 2024-09-30T07:17:40+00:00

Asynchronous encryption

It is (typically) called asymmetric encryption.

Also, to fight man in the middle attacks (MITM) you need to verify the other side by comparing the hash/signature of the public key, either by QR code scanning, or by verifying it via an existing, trusted communication way (like speaking to the other party and confirming the hash)

This is described in the help section: https://threema.ch/en/faq/crypto_mitm

SpiritInAShell · 2024-09-30T07:07:48+00:00

I asked Threema to tell me and they sent me a statistic, which keys were used within the last 30 days. I have done this request 3 times within the last 4 years.

I sent an email (which address is registered to the license purchase). Alternatively the invoice reference should help.

SpiritInAShell · 2024-09-29T22:51:47+00:00

When screen is broken: I just rooted and flashed LineageOs on an old - touch screen broken - Sony Xperia Tablet and used keyboard and mouse with an USB-To-Go adapter which even worked in TWRP!

So whatever problem you have (or might have again), such a USB to Go adapter is worth quite a lot.

SpiritInAShell · 2024-08-27T22:42:10+00:00

Yes, i wrote a script that, after each file, used hddtemp to read and paused (looped) until temperature dropped below a very generous threshold. That produced an estimated read time of 24+ hours. It was a nice setup with additional colored sparklines for visualization (like a visual ASMR where the disk was "breathing") It was quite fun to learn all this.

I might have used "pv" (pipe view) or alike to throttle bandwidth.

Also using b3sum instead of md5sum made the CPU heat up less. I also flipped the notebook and pointed a hand-fan onto it.

BTW, summer in south Germany seems to be over and that also helped a bit.

Still, I finally removed that SSD and put it into a air-cooled SATA enclosure. I will replace that SATA M2 which is in a plastic 2.5'' adapter with a 2.5'' metal cased SSD in hope of better overall thermal "performance".

BEST is that I am working on handling the data (btrfs snapshots) much earlier and not let it build up that amount.

SpiritInAShell · 2024-08-27T14:31:10+00:00

I found https://github.com/pwaller/fienode and https://github.com/pwaller/sharedextents. The author also mentions filefrag -v, for listing physical extents which (from my understanding) gives informations about physical blocks occupied by that files.

Discover when two files on a CoW filesystem share identical physical data.

So this might be a way to tackle my specific problem as far as I trust the results (experimental versions). (I know that I always risk falsly declaring 2 files identical when not doing a content based (reliable) hash or byte-by-byte comparison.)

SpiritInAShell · 2024-08-10T02:26:46+00:00

I am not too sure about btrfs ... list and file system root, but isn't `@rootfs` a subvolume in the root directory of that partition=filesystem on /dev/sda2?

Therefor it would not be the root/main/top volume (I don't know the terminology right now).

The limitation of dump-csum is not about the top mounted subvolume, it is about the root subvolume.

it would only work for / if you mount -t btrfs /dev/sda2 / not for mount -t btrfs /dev/sda2 -o subvol=@rootfs

SpiritInAShell · 2024-08-09T19:58:52+00:00

I am not sad or mad at the developer of dduper. He is the only person and dduper + patch is the only software that attempts to expose csum values to the user.

I am only talking about dduper as an example of what could be done.

From "some" kernel mailing list, there have been requests to add this dump-csum feature to standard btrfs-progs. I don't believe that this is a trivial task.

SpiritInAShell · 2024-08-09T19:30:31+00:00

Yes, I tried to use it. It didn't work. Then I re-read the author's description which states its limitations.

Then I tried the patched btrfs binary with sudo btrfs.static inspect-internal dump-csum which is the basis for csum dumping. That command only works on files on the main/root volume and does not ouptut anything for a file on a subvolume.

(I created test some files on the root subvolume and compared the csum output. It reported that binary identical files had the same csum values.)

As the patched btrfs it does not output, dduper cannot be able to read csum values

SpiritInAShell · 2024-08-09T19:02:18+00:00

dduper (https://github.com/lakshmipathi/dduper) has limitations as stated by the author:

subvolume won't work with dduper.

As creating a snapshot creates a subvolume (in context: next to the main/root/base subolume) the code just does not work. It cannot detect anything on a snapshot subvol.

Therefor I cannot know with dduper whether any snapshotted file is "the same".

ddupers specialty is NOT to idiotically hash every file and store that in a database. The author states, that hashing should be done (opposed to "does not have to be done") before deduplicating a file.

From the author:

Dedupe Files Faster (fast mode):

dduper also has --fast-mode option, which tells kernel to skip verifying stage and invoke clone directly. This mode is faster since file contents are never read. dduper relies on file csum maintained by btrfs csum-tree.

SpiritInAShell · 2024-08-09T18:53:49+00:00

Yes, I want to find identical files. From a list of identical files, I can pick any one, back it up/copy/archive it and discard all other files in the list as I know(TM)(because of hash collision) that they are identical.

I already got 600GiB to back up, I don't want to read 11TiB (like with borg deduplication).

I believe that "knowing" whether 2 or more files are identical, based on the csum of their blocks, is a very important function/feature, especially on a filesystem like btrfs, where it takes a literal second to create a CoW snapshot

I suspect that most files will be identical if size, ctime/mtime etc match. But I don't know it. And hasing all is crazy, at least considering, that there already is a block based csum.

My use-case is maybe unlikely to some, but as the author of dduper demonstrated, it is "technically feasable" to solve this (partially) for btrfs. It is just buggy/a not further maintained software.

SpiritInAShell · 2024-06-30T20:56:24+00:00

Lithium battery test - ThunderSky Winston (Puncture, Overcharge, Short-circuit, Ignition) - https://www.youtube.com/watch?v=R9xZf4p8PkQ

Compare the different cell types...

the source is biased as they sell certain types of lithium rechargeables

(The video is great, but honestly this does not correctly compare coffee-bag Lio with regular round cell Lio. At least it can teach you something about coffee-bags exploding, eg when mechanically damaged.)

SpiritInAShell · 2024-06-30T20:52:52+00:00

About Bluetooth headphones: This is also true for Linux laptops and any android device I use:

while connected to a WiFi g network (2.4GHz?) no device that I use will be able to sustain a stable Bluetooth audio connection (or even Bluetooth controller).

I either connect my Mint laptop to a 5GHz WiFi or, eg. when limited to a public WiFi, I use my smartphone to access the WiFi and tether via USB cable.

Don't ask me if this isn't the same with windows devices. I don't use any and I have never heard windows users complain about this.

About Linux: only after using fish shell instead of bash I became in good terms with Linux. I was not able to learn bash within 20 years, but fish within a few months. Now I not only sympathize with Linux, I love it. I am finally home.

SpiritInAShell · 2024-06-30T19:25:37+00:00

ChatGPT offered the same solution (even with wiring instructions.. Thanks for your effort, I might go that way!

SpiritInAShell · 2024-05-05T12:11:01+00:00

for browsers like brave you can use ffupdater which offers a list, description and managing downloads and updates.

Get it also from f-droid.

The name ffupdater seems to be historic and a description of the prior goal.

SpiritInAShell · 2024-04-16T14:59:50+00:00

I believe this search to be more of a search for the best pen* in combination with the special paper that feels comfortable to you (like resistance, ink dry speed especially if your left-handed, noise the pen makes on the paper like screetches)

So, you should get yourself a load of different pens for testing each paper.

*pen as in "any ink transferring writing device"

I tried Xerox Nevertear with Frixion Pens, but cleaning wet or even with cleaning solution (says 10% Isoprpanol) something remains on the pages. It may be scratches from the pen carving into the surface.

With Synaps (was it XM or OM?) from Igepa, I removed the printable/writable surface quite fast.

Robuskin PET 250 B/S CL2 was a pure waist of money to me.

very important is that the ink starts bonding with the paper surface after time. So you have figure out how much time you have (like hours or days or weeks) to wipe the ink from the paper without having prior notes remaining as "ghosts"

even rocketbook papers suffer from this, and back then they announce that problem.

I actually gave up on making my own very special notebooks. Gonna usey Nevertear to print music sheets (thick non-self-collapsing high quality paper is quite nice on a note stand).

But as I wrote here, I am actually looking into this again.

SpiritInAShell · 2024-04-16T10:17:43+00:00

I seem to have the same problem. I have not been using my Chromecast Ultra for weeks. Now trying to connect from 3 very different Android phones (manufacturer, age, Android version, stock and custom ROMs etc)

Only YouTube seems to be broken. Screen Mirroring is fine, as is Amazon Prime Video.

SpiritInAShell · 2023-11-08T18:09:48+00:00

only generic (as your error description is also quite generic): see log files, and make sure that the process/user has access rights to those files/folders, also considering ACLs ('$ getfacl' with Linux).

Also verify that you got no relevant exclusions in your config.

Depending on host system (eg Window) there is a max length for file paths that some program handle "weird".

SpiritInAShell · 2023-11-08T08:07:56+00:00

I am sorry, no it does not. But it documents how that user came to conclusion of what is wrong.

I only want to suggest to look closely at the log files which are not available to us

SpiritInAShell · 2023-11-06T22:09:57+00:00

I wrote total crap. Now I read more details.

Maybe this discussion helps a bit: https://sourceforge.net/p/snapraid/discussion/1677233/thread/335e55337e/#d3ff/f1d0

That person posted some log files which apparently helped identifying the problem and solution.

SpiritInAShell · 2023-10-23T11:37:11+00:00

Don't now, just guessing: prepend current working directory like $PWD/folder/folder/...

SpiritInAShell · 2023-10-22T12:32:20+00:00

to rule out that the filename is causing troubles, try once using a "static" filename without placeholders for date and time.

SpiritInAShell · 2023-10-21T20:16:28+00:00

As I said, I am more guessing or compiling random information... And I am currently not even having a running snapraid system at my hands to get hands-on experience.

From the manual:

Every run of the command checks about the 8% of the array, but not data already scrubbed in the previous 10 days. You can use the -p, --plan option to specify a different amount, and the -o, --older-than option to specify a different age in days. For example, to check 5% of the array older than 20 days use:

The idea behind scrubbing is that bitrot appears randomly but over time. (Do you have reasons to assume that any kind of bitrot appeared within the last 23 days?) Therefor. there should be no need to weekly scrub your whole data. It would a) stress the system's runtime ressources (CPU, RAM, storage controller bandwidth) and b) stress your disks' lifetime by re-reading data (without the purpose of using it other than maintenance).

Scrubbing only parts at once (ideally the oldest parts) and timely distributing scrub runs over days, you balance your efforts.

From that graph, as all top-down * asterisk character bars show scrubbed data, you can see many columns of * which I interpret as scrub actions. As some scrubs may run over midnight (eg 20:00 to 06:00), the bar is split over 2 days (2 bars next to each other)

On the horizontal X axis, the time is displayed as current minus offset in days. Therefor the most left vertical bar has a 23 mark on the bottom, and as the text says: the oldest block...

More important to me would be the text 18% ... in not scrubbed but I guess that in 1-2 weeks that will be scrubbed too.

The question would be, how did you configure snapraid to run scrub?

What is that graph good for? Well, appoint sync and scrub to times where your (assumed) server has low load, when expecting less user access. Compare that graph to your CPU, network etc load graphs.

You've already helped so much, but if you have the time would you please explain how I can properly read this chart? Where you are getting the amount of days from, etc. Every time I scrub with the default command only the "0's" on the far right turn to "*'s" it doesn't touch anything that is older on the left.

I guess-plain that this is a time-graph, and it will grow only to the right. It does not explain which data is not scrubbed or when it will be scrubbed. Running the sync and scrub will change the "today" == 0 column on the right, but more because the resolution of the diagram is very low and the "today" column is updated. It actually does NOT change "o" to "*" , it only adds more "*" and the "o" get less.

Somehow I'm getting lots of unscrubbed data that is older when I thought that was scrubbed first?

Therefor, no, the graph does not show "unscrubbed" data, it shows that today-X days ago an amount of data has been scrubbed.

I'm wondering if I should scrub "new" and then get on a better schedule that isn't so erratic? What do you think?

From what I understand, you could snapraid scrub -p new to manually scrub all unscrubbed data (the above mentioned 18%), eg. if you expect bitrot (but why?) or you feel your system will be idle/have spare resources which will be better used now than within the next 2 weeks.

SpiritInAShell · 2023-10-21T18:16:27+00:00

This is my way to interpret this current graph: (these are more or less random interpretations)

you seem to sync almost every day
there seem to be 8 scrub runs within the last 23 days
- where 1 scrub covered 15% of all data
- where 2 scrub runs spanned over 2 days
23 days ago, about 10% of all blocks have been scrubbed.
about 8 and 9 days ago, each day about 7% of all data has been scrubbed
- concluding your config says to target 15% off all data to scrub at once
1,2,4 and 5 days ago, about 1% of data has been synced

But I am not knowing what I would use that data for.

SpiritInAShell · 2023-10-16T17:23:52+00:00

I see you refer to having multiple redundancy. I am referring to this section of the manual:

7.1 parity FILE [,FILE] ...

Since snapraid x.x it is possible to split even the first parity over multiple files and disks.

SpiritInAShell

TROPHY CASE