Creating a specific hash setup

While solving a practice exam, this is the question I could not answer. Any help is appreciated. I am new to hashing and have no idea how to solve this question.

Let $ H$ be a $ (0.15, 0.85, 0.9, 0.1)$ -sensitive family of hash functions. Suppose we use 60 functions from $ \cal{H}$ to sign the documents and apply an AND followed by OR construction using $ b$ bands and $ r$ rows within each band (hence $ b$ and $ r$ are whole numbers with $ b \cdot r = 60$ ).

For any two documents to be considered a candidate pair, their signatures will need to match in all the $ r$ rows of at least one band. For a similarity threshold of $ 0.15$ , we would like the construction to yield a false positive rate of at most $ 0.05$ and for a similarity threshold of $ 0.85$ , we would like the false negative rate to be at most $ 0.1$ – explain clearly whether or not this is possible, and if so, to provide appropriate values for $ b$ and $ r$ that will achieve the desired rates.

c# – Setup specific mousewheel rules and timer with reset function to control a value with minimal user input

My main issue here is to distinguish a first and a second stage when moving a mousewheel up and down.
How could I put the following together for a mousewheel solution in plain c#?
I have a value that controls the opacity level of an object and it could be a value between 1 – 255.
I started with a simple mousewheel setup so that each time the wheel jumps to its next spot upwards or downwards, another value returns a 1 or -1. What I need is moving the wheel up or down 1 time will start a timer event that changes the opacity value to the minimum or maximum value depending on wheel movement direction by adding/subtracting 1 to the current value every 1ms. For up direction, stop value increase only when the wheel was moved to the next spot upwards or when the value is 255. For down direction, stop value decrease only when the wheel was moved to the next spot downwards or when the value is 1.

Shadowsocks Setup Advice [migrated]

I needed some advice on how to setup my shadowsocks iOS client on my school internet

The school internet is routed through a proxy server (which has to be setup in your device settings in order for it to work).

I’ve tried setting up and connecting to the sever normally without changing any of the advanced settings but there is no internet access.

If anyone could provide some advice, it would be greatly appreciated

I will create, setup and launch shopify dropshipping store for $65

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by: haksxsx
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Category: Programming
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Multi monitor – multi gpu setup – rendering

im having an issue with my setup and i dont know the correct technical term to search for, so i’m trying to describe my problem as best as i can.

I have three monitors connected to two GPU’s – 1st GPU is an Nvidia 2nd one is the intel iGPU build into the processor.

Left Monitor (Intel) Middle monitor (nvidia proprietary) right Monitor (intel). Ubuntu 19.04 autimaticly sets up one big x screen with all three monitors in it. I can maximize windows on all acreens and they are maximized to the screen they are currently one. I can drag windows from screen to screen – that all works.

But it seems the nvidia card has to do all the work. For example if im starting firefox and open up a youtube video, the nvidia card decodes it although its displayed on a monitor connected to the intel iGPU. I would like the nvidia gpu only do the work for the screen it’s connected to and have the intel iGPU only deal with all stuff that happens on its screens.

I dont know how to achieve this nor do i know the correct term to look for on the web.

Thanks for your help :).

Step by step guide for doing Wireguard VPN security and setup properly, for Android phone to LAN

Truism: Doing security right, is subtle and full of snags for the clueless.

Concern: I haven’t ever set up a connection between 2 computers using RSA/SSH keys or certificates, in my life. Realistically, I’m very aware of the theory, and I’ve read most of the steps piecemeal in security writeups, but for practical purposes, I’m still one of the clueless (for now).

Conclusion: Step by step help appreciated, so I do my Wireguard setup right, and also begin to learn “properly” and gain confidence for future connections (whether they are certificate or key based – SSH, 802.1X, web HTTPS certs, etc).

My setup

I’ve tried to follow the principle that what I can’don’t know enough to do reasonably safely, I at least try to avoid and not do insecurely.

LAN gateway – runs OPNSense FreeBSD soft router (fork of pfSense running on HardenedBSD, a hardened derivative of FreeBSD, so I can use pfSense analogies and find the same functionality on mine if needed). There’s separate NICs for wired and wireless LAN. Almost all wireless traffic is blocked from the LAN, so I’d open a port for “trusted device” traffic and then limit its access according to minimum needs (no help sought on that).

Wifi AP – The router’s wifi NIC is connected by ethernet to an OpenWRT Wifi router. Because it’s got virtually zero access to the LAN (ping router NIC and reach one dumb isolated printer server IP/port) and can only reach the WAN, there’s actually no security on this at all at the moment (I don’t have a problem running an open wifi network where I am; I’m also running a public tor exit node on one IP on the LAN).

Network services – DHCP4 and Unbound (resolver) on the router. No AD/directory services. No certificates/CA/RSA in use currently except automatically created ones for router/file server WebUI etc. Password based logins (ugh! Hope to learn + fix that someday!).

Mobile phone – Runs LineageOS 16 (Android Pie) with MicroG (FOSS Google services package replacement). Would like to move to 802.1X but again, lack knowhow of the certificate or key setup process done right.

VPN software – Wireguard seems quite well suited to my situation – I use public transport a lot, and theres a lot of intermittent disconnection and short lived reconnects, so a FOSS VPN that needs less config, auto uses decent tunneling setup, seems well reputed, and is designed for quick reconnects, seems better for me than, say, OpenVPN, although I’m sure both would work.

VPN endpoint/IPs – The VPN terminates on the OPNSense router so the open Wifi device isn’t an issue. The LAN uses 192.168.0.0/16, with 192.168.0.1/20 allocated for router, static, DHCP, and all non-VPN devices. So I can use 192.168.32.0/24 for any VPN-connected devices.

Broadcast domain – I’d like to have level 2 OSI broadcast not just switching, I * think * this is typical with VPN but not sure? I don’t expect broadcasts to flood the network 🙂

Likely usage/purposes

  1. SSH/FTP/SMB/RDP/ADB-over-TCPIP and perhaps media streaming between phone and LAN devices. Moving 20-40 GB dirs between phone and file server will become much quicker if I can use Wifi (when available) instead of waiting till home and using USB/SDCard.
  2. VPN tunnel to route all phone network traffic via LAN when away from home when using unknown wifi networks
  3. Moving some functionality from phone to LAN (Example: calendar/notes/feed via a LAN-based web server rather than locally as phone apps).
  4. Once more confident, doing similar for laptop, to allow remote working from laptop via VPN to LAN via RDP.

VPN security choices

A large part of any key/cert setup is about “how secure/hardened do you want to make it?” To make this simple, assume “hard enough that I probably don’t have to worry for 15 years”, other than deal with any publicly identified vuls (which I’ll leave to the software writers to fix). Assume plenty of CPU power for more rigorous at both phone+LAN ends, and roughly, enterprise level rather than home LAN style security for the VPN aspect. Meaning, I’d like to begin learning to do it right, even if patchwork/piecemeal at first (I’d like to avoid “no point in doing much, as more serious vuls exist”).

So I’m happy to use RSA 4096 rather than 2048, or more processor intense but secure algorithms; if a cert is needed, I’d rather have steps that create an intermediate CA so I can keep my top level CA totally offline. If there’s additional hardening options that a conscientious security pro would choose for say, CEO/CFO of a SME size business, that’d be about my kind of level.

Threat model

Mobile phone – overall I’d treat it as trustworthy. AFAIK I haven’t ever had a security issue with it, or an unsafe app, and in a way it’s unavoidable that I need to trust it somewhat. I can also set rules to block all but limited usage, either in the router or in my main servers, so that it’s got limited capacity for usage/harm and no root access to any device even if exploited. But that’s separate.

Connectivity/tunnels – I don’t feel comfortable just with WPA2/PSK. I’d like to ensure its the actual expected device, via some form of mutual authentication, if there’s a way to do it. Hence even where I can trust the network, at home, I’d like not to just connect via WPA2, but only via VPN, even if I’m going to access the LAN from my phone while at home, using my home router.

Own ignorance of correct setup+security processes/good practices for this – See below. I think this, and threats arising from it, are the main risk. I’m especially thinking, if I open the LAN to one device, I’ve potentially opened it to all, so I need to make sure I do only open it to that one device, as best I can, and not to others. I think that’s the biggest risk, and the motive for the question.

SUMMARY WHAT I AM HOPING FOR

I’m worried about my “Unknown unknowns”.

I don’t know what keys/certs I might need, nor how to correctly generate them. There are writeups but not a good start-to-end walkthrough I feel comfortable with. Basically, what recommended software+commands to use? What is good practice for the settings/CLI options/config used to generate them? What .conf settings should I also consider setting in Wireguard’s server/client?

I also don’t know which if any keys/files to generate on a “known safe” machine, and which if any files generated, should be stored airgapped/offline. I think it’s pretty much that simple.

So what I’m hoping for is a step by step recipe for my 1st time. A bit like this –

“Use package X or Y on BSD. These are the important switches/config choices. Use (or don’t use) a password. These are the commands to run on package X, or these commands on package Y. 3 files/keys will be generated. Put this one here and that one there. Hide this one on an airgapped system or USB stick. Configure Wireguard server/client .conf with these extra options. Done.”

I’d like to use CLI packages such as OpenSSL (already installed) rather than the router’s built-in GUI functionality, to generate any keys/certs, as this will help me be more competent in future.

Hopefully if I get this right, I’ll also learn quite a lot of what I need, to do other (certificate|priv+public key) based connections like 802.1X and SSH properly, both between the mobile devices and the OpenWRT bridge, and between LAN devices, and also be well on my way to getting RADIUS or other AAA running at some time to harden the LAN a bit more internally.

How to setup site with second specialised domain name with same content

I got a website: company-name-counselling.co.uk

I have setup all 4 versions of the domain to redirect to the https://www.company-name-counselelling.co.uk

I have also bought nearby-town-counselling.co.uk and other-town-counselling.co.uk

I want this site to appear in google when people search for counselling in nearby town.

I will update the title of the home page to include nearby-town when accessed on this domain but the content will mostly stay the same.

Will I benefit from having a specific domain for nearby-town or will the duplicate content penalise me?