Is a VPN and Virtual Machine secure enough for running programs that might include malware

I am trying to start a LEGAL business online but don’t want viruses from any sketchy software that I will be downloading. I will be using a VM and a VPN but was wondering if I needed any other software so my computer, network etc will not be affected. I understand not to have shared files on and all that but still don’t know for sure because some people say some malware can get through Virtual Machines. Thank you for reading and please reply if you can provide any assistance.

Upper bound for runtime complexity of LOOP programs

Recently I learned about LOOP programs, which always terminate and have the same computational power as primitive recursive functions. Furthermore primitve recursive functions can (as far as I understood) compute anything that isn’t growing faster than $ Ack(n)$ .

Is this implying that the upper bound runtime complexity for LOOP programs is $ O(Ack(n))$ ? And are there functions similar to Ackermann’s function, which can’t be computed by primitive recursive functions, but grow slower than $ Ack(n)$ ?

(sorry for spelling and grammar)

Cycling windows by click on dock program’s icon

By now, when I click to an application in my dock it is minimized. But I would like to cycle through all open tabs of that application with this action.

I use to use the Super+number hot keys to toggle between programs, however, by this, it show me the system activities while there is multiple tabs of the target application.

How could I change this behavior?

Securely distributing passwords and salts that will be derived by client programs

I am creating a client-server architecture running on top of the KCP protocol in Go. The package for KCP that I’m using is KCP-Go (https://github.com/xtaci/kcp-go). The package supports packet-level encryption and FEC. To use the packet-level encryption feature, I need to generate an AES key. Following the latest OWASP recommendations for securely storing passwords and keys, this is what I’ve done thus far:

  • I have generated a 64-byte password and salt.
  • I pass that to PBKDF2, using (600000 * num_cpus) rounds, and requesting a 32-byte key.

Now I am wondering how to exactly securely distribute this key. At this time, I start up another TCP server and allow clients to connect. When they do, I send them the password, salt, number of iterations, and checksum hashes for those three to ensure they’re not tampered with, and allow the client to perform key derivation. My question is: Is this method of distribution actually secure, or should I find some other way (i.e. using public keys)? If there is a more secure method to allow clients and the server to communicate, what should I do instead? I should note that when clients and servers send messages to one another a hash of the message is included along with the message to allow clients to verify the messages validity (I’m using SHAKE256). The hash funciton used during key derivation is BLAKE2B (though I have thought about using Argon2).

Ubuntu 18.01 favorite programs menu selections have reverted back to default selection

I’m running ubuntu 18.10. I have my file system split on two drives, /home is on a 1T drive and my /root is on an 250G SSD.

Every once in a while, I’ll have to reboot the system (lockup of some such problem), when I log back on my sidebar menu selections have reverted back to the default (initial install) selections. I’ve been occasionally successful in restoring them by turning off the system (power down) and bring it backup. However, sometimes they do not… I just happened and they appear to be lost. This happened as well on ubuntu 16.10

Any ideas? Thanks Wayne

Unity settings and programs got messed up after fsck disk check

While doing my normal activity on my Ubuntu 16.04 (Unity) machine I noticed that Firefox stopped playing sounds from any tab (Applications tab in Sound Settings had something unknown to me listed several times and nothing else). Also the keyboard layout switching stopped working, while the indicator in the panel worked fine. I decided to reboot and after that saw the BusyBox prompt telling me that I had errors in my file system and needed to run fsck.
A similar thing happened to me about a year ago, but this time after running it on the specified drive and pressing y to every found error I typed reboot, logged back into my system and saw that the fonts are different from default and the theme switched back to Ambiance (from Radiance).
Nautilus changed it’s layout to (probably) non-patched gnome version, with nothing in the global menu. The ‘Recent’ folder returned despite still being turned off in the settings.
Image Viewer now has both global menu and local, under the title bar menu. Firefox got it’s icon changed to a folder.
Some programs wouldn’t start at all, including gedit and gnome-terminal. Running them in xterm outputs:

Failed to import the site module Traceback (most recent call last):   File "/usr/lib/python3.5/site.py", line 78, in <module>     import os   File "/usr/lib/python3.5/os.py", line 27, in <module>     import stat as st ImportError: No module named 'stat' 

Between some more reboots the fonts and the theme had partially changed to the selected, and then back again.
Each time after logging in the mouse buttons wouldn’t respect the settings (mine are set to RMB as primary), the settings page is correct, but after a while the screen goes black for a second and it is back to normal.

What may have caused this and how can I fix it? Thank you.

Sorry if something isn’t clear, I’m writing this late.

Additional, but possibly unrelated information:
Some strange bug causes my computer to turn on right after the shut-down. I dual-boot with Win7 and this only happens with Ubuntu, and only for the past 2 or so years. After a cursory search I was not able to find a solution to this and got used to turning it off from the back of the case right after it starts again.
During the last several months I had 3 times when my computer suddenly rebooted while I was doing something. I hadn’t yet investigated that.
The disk with Ubuntu is just ~45 gb and currently I work with mostly less than 400 mb on the ‘/home’ partition and 1.2 gb at ‘/’.
The hardware is also mostly more than 10 years old.