Showing posts with label works. Show all posts
Showing posts with label works. Show all posts
Tuesday, November 1, 2016
What is CAPTCHA and How it Works
What is CAPTCHA and How it Works
CAPTCHA or Captcha (pronounced as cap-ch-uh) which stands for “Completely Automated Public Turing test to tell Computers and Humans Apart” is a type of challenge-response test to ensure that the response is only generated by humans and not by a computer. In simple words, CAPTCHA is the word verification test that you will come across the end of a sign-up form while signing up for Gmail or Yahoo account. The following image shows the typical samples of CAPTCHA.
Almost every Internet user will have an experience of CAPTCHA in their daily Internet usage, but only a few are aware of what it is and why they are used. So in this post you will find a detailed information on how CAPTCHA works and why they are used.
What Purpose does CAPTCHA Exactly Serve?
CAPTCPA is mainly used to prevent automated software (bots) from performing actions on behalf of actual humans. For example while signing up for a new email account, you will come across a CAPTCHA at the end of the sign-up form so as to ensure that the form is filled out only by a legitimate human and not by any of the automated software or a computer bot. The main goal of CAPTCHA is to put forth a test which is simple and straight forward for any human to answer but for a computer, it is almost impossible to solve.
What is the Need to Create a Test that Can Tell Computers and Humans Apart?
For many the CAPTCHA may seem to be silly and annoying, but in fact it has the ability to protect systems from malicious attacks where people try to game the system. Attackers can make use of automated softwares to generate a huge quantity of requests thereby causing a high load on the target server which would degrade the quality of service of a given system, whether due to abuse or resource expenditure. This can affect millions of legitimate users and their requests. CAPTCHAs can be deployed to protect systems that are vulnerable to email spam, such as the services from Gmail, Yahoo and Hotmail.
Who Uses CAPTCHA?
CAPTCHAs are mainly used by websites that offer services like online polls and registration forms. For example, Web-based email services like Gmail, Yahoo and Hotmail offer free email accounts for their users. However upon each sign-up process, CAPTCHAs are used to prevent spammers from using a bot to generate hundreds of spam mail accounts.
Designing a CAPTCHA System
CAPTCHAs are designed on the fact that computers lack the ability that human beings have when it comes to processing visual data. It is more easily possible for humans to look at an image and pick out the patterns than a computer. This is because computers lack the real intelligence that humans have by default. CAPTCHAs are implemented by presenting users with an image which contains distorted or randomly stretched characters which only humans should be able to identify. Sometimes characters are striked out or presented with a noisy background to make it even more harder for computers to figure out the patterns.
Most, but not all, CAPTCHAs rely on a visual test. Some Websites implement a totally different CAPTCHA system to tell humans and computers apart. For example, a user is presented with 4 images in which 3 contains picture of animals and one contain a flower. The user is asked to select only those images which contain animals in them. This Turing test can easily be solved by any human, but almost impossible for a computer.
Breaking the CAPTCHA
The challenge in breaking the CAPTCHA lies in real hard task of teaching a computer how to process information in a way similar to how humans think. Algorithms with artificial intelligence (AI) will have to be designed in order to make the computer think like humans when it comes to recognizing the patterns in images. However there is no universal algorithm that could pass through and break any CAPTCHA system and hence each CAPTCHA algorithm must have to be tackled individually. It might not work 100 percent of the time, but it can work often enough to be worthwhile to spammers.
Available link for download
Sunday, October 16, 2016
What is RAM and How RAM Works
What is RAM and How RAM Works
What is RAM and how does it affect your computers performance? Read on for a plain English definition of RAM and find out how RAM works in a computer.
What does RAM stand for: Random Access Memory (also known as memory, main memory, system memory)
Lets begin with the name: Random access refers to the fact that data that is stored anywhere on RAM can be accessed directly regardless of its (random) location. This is in contrast with other types of data storage such as hard disk drives and discs where they have to spin to the datas location first before being able to access it.
RAM is essentially memory chips soldered onto a stick of circuit board. Since a picture speaks a thousand words, lets meet our RAM stick (also called a RAM module):
To understand how RAM works and the role it plays in a computer, well first have to learn a few of its important properties:
Super fast, volatile and relatively expensive... So what is RAM used for in computers?
Whenever you run a program (e.g. operating system, applications) or open a file (e.g. videos, images, music, documents), it is loaded temporarily from the hard drive into your RAM. Once loaded into RAM, you will be able to access it smoothly with minimal delays.
If you run out of RAM, your operating system will begin dumping some of the open programs and files to the paging file (see image below). This is bad news... because your paging file is stored on the much slower hard drive. So instead of running everything beautifully off RAM, a part of it is being accessed from your hard drive.
This is when you will begin to notice awful things like slow loading times, stuttering and general unresponsiveness (especially if you have a mechanical hard disk drive).
So now we know what is RAM used for: Having enough RAM allows your computer to be more responsive, multitask better and run memory-intensive programs (e.g. video editors, databases, virtual machines) with ease.
What does RAM stand for: Random Access Memory (also known as memory, main memory, system memory)
Lets begin with the name: Random access refers to the fact that data that is stored anywhere on RAM can be accessed directly regardless of its (random) location. This is in contrast with other types of data storage such as hard disk drives and discs where they have to spin to the datas location first before being able to access it.
RAM is essentially memory chips soldered onto a stick of circuit board. Since a picture speaks a thousand words, lets meet our RAM stick (also called a RAM module):
- RAM is blazing fast compared to hard drives - Even the latest and greatest solid state drives are embarrassingly slow when pitted against RAM. While top end solid state drives can achieve transfer rates of more than 1,000 MB/s, modern RAM modules are already hitting speeds in excess of 15,000 MB/s.
- RAM storage is volatile (temporary) - Any data stored in RAM will be lost once the computer is turned off. Comparing computer storage to the human brain, RAM works like short term memory while hard drives resemble our long term memories.
- RAM is more expensive than hard drives - Even with RAM prices tumbling to new lows with each passing year, RAM will always cost more per gigabyte. This is to be expected given RAMs massive speed advantage. Lets compare the average prices of RAM vs hard drives at the time of writing:
| Price per GB | |
| RAM | US$5.50 per GB |
| Solid State Drives | US$0.80 per GB |
| Hard Disk Drives | US$0.04 per GB |
Whenever you run a program (e.g. operating system, applications) or open a file (e.g. videos, images, music, documents), it is loaded temporarily from the hard drive into your RAM. Once loaded into RAM, you will be able to access it smoothly with minimal delays.
If you run out of RAM, your operating system will begin dumping some of the open programs and files to the paging file (see image below). This is bad news... because your paging file is stored on the much slower hard drive. So instead of running everything beautifully off RAM, a part of it is being accessed from your hard drive.
So now we know what is RAM used for: Having enough RAM allows your computer to be more responsive, multitask better and run memory-intensive programs (e.g. video editors, databases, virtual machines) with ease.
Available link for download
Friday, September 9, 2016
What is XMPP and How SSL TLS works
What is XMPP and How SSL TLS works
What is XMPP
Guys, XMPP is largely used for the message servicing. Most of the top companies are using this for their messaging.
Extensible Messaging and Presence Protocol (XMPP) is a communications protocol for message-oriented services based on XML.
It is a protocol based on Extensible Markup Language (XML) and intended for instant messaging (IM) and online presence detection. It functions between or among servers, and facilitates near-real-time operation. The protocol may eventually allow Internet users to send instant messages to anyone else on the Internet, regardless of differences in operating systems and browsers.
XMPP is sometimes called the Jabber protocol, but this is a technical misnomer. Jabber, an IM application similar to ICQ (I Seek You) and others, is based on XMPP, but there are many applications besides Jabber that are supported by XMPP.
Eventually, XMPP is expected to support IM applications with authentication, access control, a high measure of privacy, hop-by-hop encryption, end-to-end encryption, and compatibility with other protocols.
IBM and Microsoft are working on a similar standard called SIP for Instant Messaging and Presence Leveraging Extensions (SIMPLE) based on Session Initiation Protocol (SIP).
How SSL &TLS works
Mostly asked question that why the S is displaying after HTTP..
A popular implementation of public-key encryption is the Secure Sockets Layer (SSL). Originally developed by Netscape, SSL is an Internet security protocol used by Internet browsers and Web servers to transmit sensitive information. SSL has become part of an overall security protocol known as Transport Layer Security(TLS).
 Look for the "s" after "http" in the address whenever you are about to enter sensitive information, such as a credit-card number, into a form on a Web site. |
In your browser, you can tell when you are using a secure protocol, such as TLS, in a couple of different ways. You will notice that the "http" in the address line is replaced with "https," and you should see a small padlock in the status bar at the bottom of the browser window. When youre accessing sensitive information, such as an online bank account or a payment transfer service like PayPalor Google Checkout, chances are youll see this type of format change and know your information will most likely pass along securely.
TLS and its predecessor SSL make significant use of certificate authorities. Once your browser requests a secure page and adds the "s" onto "http," the browser sends out the public key and the certificate, checking three things: 1) that the certificate comes from a trusted party; 2) that the certificate is currently valid; and 3) that the certificate has a relationship with the site from which its coming.
 The padlock symbol lets you know that you are using encryption. |
The browser then uses the public key to encrypt a randomly selected symmetric key. Public-key encryption takes a lot of computing, so most systems use a combination of public-key and symmetric key encryption. When two computers initiate a secure session, one computer creates a symmetric key and sends it to the other computer using public-key encryption. The two computers can then communicate using symmetric-key encryption. Once the session is finished, each computer discards the symmetric key used for that session. Any additional sessions require that a new symmetric key be created, and the process is repeated.
Available link for download
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