denial of service – Forcing a machine to occupy a part of RAM for a period of time to prevent it from DoS attack

In order to prevent the participants in a distributed network from Sybil or DoS attacks, one of the solutions is PoW (either compute-based or memory-based).

As an alternative to existing PoW techniques, we would force the participating machines in the network to occupy a part of their RAM memory for a period of time (as a resource consuming approach),

Then, there are two questions:

  1. Is such an approach feasible in practice and programmable ? (for example, using memory access techniques in C language)
  2. If yes, how is the rest of the network able to verify if a participant did the memory occupation procedure ? (as unlike PoW, here there is no proving mechanism.)

P.S. This approach is inspired of following memory-bound definition:

A memory-bound function should access locations in a large region of
memory in an unpredictable way, in such a way that caches are
ineffective.

If the question is not still clear enough, please let me know.

visas – Canadian PGWP expiring in September: chances of entry denial at border?

For temporary foreign workers (not to be confused with TFW program), you may be able to enter Canada if you meet specific requirements for your travel to be essential.

If you are normally a resident of Canada (e.g. you were just on vacation in India for a few weeks until the crisis), you can almost definitely return.

Otherwise, you will need your port of entry letter/letter of introduction and a confirmed job offer. You can ask CIC if you qualify (if you can get through to an agent, they are usually helpful.)

Travel restrictions and exemptions for temporary workers

As a temporary worker, you’re exempt from travel restrictions if
you’re coming for an essential (non-discretionary) purpose.

Certain people who can work without a permit may also be exempt from
travel restrictions. Essential (non-discretionary) travel for a
temporary worker

Essential refers to travel for reasons that are non-discretionary and
non-optional. The emergency orders under the Quarantine Act do not
allow people to travel to Canada for optional or discretionary
reasons, such as for tourism, recreation or entertainment.

As a worker, your travel is essential (non-discretionary) if you’re in
either of these situations:

  1. You have a valid work permit and normally live in Canada.
  • This applies even if you’ve been laid off.
  1. You’re a worker who meets all of the following:
  • has a letter of introduction for a work permit (open or employer-specific)
  • has a valid job offer
  • can work once you enter Canada and complete your 14-day quarantine (unless you’re exempt)

https://www.canada.ca/en/immigration-refugees-citizenship/services/coronavirus-covid19/foreign-workers.html#restriction

Canada – Denial of UK visit visa with 10-year ban: effect on Canadian visa application

i am indian national
I applied for a UK visitor visa and it was rejected with a 10-year ban on traveling to the UK, from 2015-2025.

I am planning to apply for the Canada General Visitor Visa, my girlfriend lives in Toronto, Canada. I want to see. In this, my prior travel ban will apply to the Canadian visitor visa. Please let me know.
thanks in advance.


This was due to the problem of forgery documents, the company I work with has not informed ukba of my salary details. after that i quit and started a new limited liability company with my partner
it was in 2008

Canada – Denial of UK visit visa with 10-year ban

i am indian national
I applied for a UK visitor visa and it was rejected with a 10-year ban on traveling to the UK, from 2015-2025.

I am planning to apply for the Canada General Visitor Visa, my girlfriend lives in Toronto, Canada. I want to see. In this, my prior travel ban will apply to the Canadian visitor visa. Please let me know.
thanks in advance.

ssh – openSSH does not reveal reason for permission denial

I have configured public key authentication on my VPS and disabled password logins.
If someone tried to connect to my VPS, it now says "Permission denied (publickey, gssapi-keyex, gssapi-with-mic)".

I don't feel very comfortable with people who know that I have set up public key authentication, I want the bad guys to know as little as possible about my secret stash.

How do I prevent openSSH from telling all my secrets?

Thank you

firewalls: how intelligent ddos ​​mitigation systems (IDMS) mitigate denial of service attack

There are many solutions, eg. Akamai and Cloudflare, suggested strategies, devices, or network architectures to mitigate DDOS attacks, but due to some basic concepts like limited bandwidth or some common / known vulnerabilities, there is no simple and complete solution for this unique problem.

In this case, I'm asking about the type of DDOS attack that has some malicious intent behind it, not the type that normally occurs when there are too many requests to some website, app, or other similar cases.

Why is IDMS more effective in mitigating complex application layer DDOS attacks than IPS / Firewall?

Canada – Visa denial. 179 (b) of the IRPR – What to include?

What can I include so that the visa officer does not think I would like to stay in Canada?

• I am not satisfied that you leave Canada at the end of your
remain as a temporary resident, as provided in paragraph 179 (b) of the
IRPR, according to the purpose of your visit.

• I am not satisfied that you leave Canada at the end of your
remain as a temporary resident, as provided in paragraph 179 (b) of the
IRPR, based on your family ties in Canada and your country of
home.

I am attending a cousin's wedding in Canada. I was planning to stay with her for 2 weeks.

I included her invitation letter with details about her wedding and that I will keep her, her passport along with her husband's passport and the wedding invitation.

I included details about my family in my country of origin and that they were not with me.

Some additional information:

  • I am from India.
  • My airline tickets in and out of Canada were reserved and provided.
  • I am self-employed and have provided my business registration in India and my business registration in the UK along with commercial bank documents and sufficient funds.
  • I provided the travel history with 4 UK visas, Schengen Visa, UAE Visa.
  • I provided sufficient personal funds to demonstrate that I have no reason to stay in Canada.
  • I included a photo of us together.

There are Regulated Canadian Immigration Consultants (RCIC) that I can hire but that cost is too high.

Any advice?

schengen – Visa denial of the Netherlands on March 17, 2020

This decision means what? Sufficient justification was not provided for the purpose and circumstances of the planned stay. The specific purpose for which the visa was applied for is no longer valid or will cease to be valid before it reaches the destination member state. No other (secondary) purpose was stated at the time of request, otherwise insufficient documentation was provided to demonstrate the purpose of the stay. Therefore, your visa application is rejected.

TCP Sequence Number Approach based on denial of service

I installed Ubuntu 16.04 64-bit desktop O. S and configured apache2 web server but while doing Qualysis analysis I get lower vulnerability.
"Denial of service based on approximation of TCP sequence number"
Can someone help me with this

customs and immigration: is entry denial possible for passport holders / residents of the country of origin?

Is there a country on earth that can legally deny entry of its own citizens to that country?

I am excluding transit to different countries to reach the destination.

It is also irrelevant to the answer about what happens after the person has entered the country (such as arrest or quarantine)

I'm specifically asking if a national of a country (holder of the passport of these countries) or resident of a country (with a valid residence permit for that country) is standing at the border, can they be legally denied entry?