So here I thought of sharing my git workflow for my personal and work related projects. Here on I’ll be illustrating setup for two accounts : personal and work.

Setup SSH key for both accounts

Context

There are multiple ways two connect your machine to your GitHub account hosted on GitHub server, such as GitHub CLI, SSH and deprecated http login.

If you have just one single account in your machine I’ll suggest you to use github CLI, it’s easy, fast and beginner friendly.

But for multiple accounts using SSH setup is the best way. So let’s start :

Create SSH keys

Let’s first generate SSH key for your personal account.

While running below command the terminal will ask for a paraphrase, you may leave it blank and hit enter. Also the email id and username need not to be exactly same as your actual credentials. The -C flag is a comment and -f flag is the file name where your key will be stored.

     $ cd ~/.ssh
     $ ssh-keygen -t rsa -C "keshav@gmail.com" -f "keshav_git"

Now repeat the same step for your work account.

  $ cd ~/.ssh
  $ ssh-keygen -t rsa -C "keshav_work@gmail.com" -f "keshav_work_git"

Add SSH keys to SSH agent

Your machine has a SSH agent to keep track of all SSH keys and use them while making SSH connections.

ssh-add -K ~/.ssh/keshav_git
ssh-add -K ~/.ssh/keshav_work_git

Add SSH keys to your GitHub Accounts

Inside the ~/.ssh directory you will find two public keys file with the name as keshav_git.pub and keshav_work_git in my case. You can open these files in any of text editor of your choice such as Vim, nano, kwrite , notepad etc.

Let’s first open the keshav_git.pub file, it’s my ssh key for personal account. Copy the content of this file and paste it on your personal GitHub account as instructed below.

• Goto Settings > SSH and GPG keys > New SSH Key

• Paste your copied public key and give any easily identifiable name such as my_windows_machine etc.

Repeat the above steps for you work account as well.

Creating a config file

Create a file with the name `config` inside your ~/.ssh directory. Edit as per your naming convention and copy the below content inside config file.

     #keshav-personal account
     Host github.com-keshav-personal
          HostName github.com
          User git
          IdentityFile ~/.ssh/keshav_git

     #keshav-work account
     Host github.com-keshav-work
          HostName github.com
          User git
          IdentityFile ~/.ssh/keshav_work_git

Using new setup for using GitHub

With this setup you can clone and make changes in your personal and work related repositories. For example I want to clone my private repository which has the SSH url as

git@github.com:alpha951/keshav_private_repo.git

To clone this repo I need to run below command in my terminal. Note that I’ve modified git@github.com to git@github.com-keshav-personal this will ensure that my shell automatically fetch ssh key from ~/.ssh/config file with hostname as github.com-keshav-personal which is my personal GitHub configuration.

git clone git@github.com-keshav-personal:alpha951/keshav_private_repo.git

Make sure you push commits with correct author name

While working with multiple git accounts you don’t want to make a commit in your work repository with your personal git username. To avoid this just set the repository specific username in the cloned directory.

So for instance if I am working on my personal repository I’ll make sure to set below username and email in my cloned repository so it will override the globally setup username. GitHub identifies contributor’s GitHub profile using their emails so it’s the most that you set correct email in your repository.

git config user.email "keshav950personal@gmail.com" && git config user.name "alpha951"

Add correct remote origin to your cloned repository

To push or pull to the correct account we need to add the remote origin to the project. So for the example we discussed before I’ll use below command to setup correct remote origin.

 git remote add origin git@github.com-keshav-personal:alpha951

To update remote origin for existing repository you can use below command

git remote set-url origin git@github.com-keshav-personal:alpha951/keshav_private_repo

Now you can simply use git pull and git push commands to update your local projects and commit contributions to the remote.

The Pitfalls of Weak Cipher Modes

Consider the following code snippet:

Cipher cipher = Cipher.getInstance(ALGORITHM);

While this might seem innocuous at first glance, it opens the door to potential vulnerabilities if not configured properly. Let's delve into some common pitfalls:

Weak Cipher Modes: CBC and ECB

In the realm of symmetric encryption, the Cipher Block Chaining (CBC) and Electronic Codebook (ECB) modes are notorious for their susceptibility to attacks.

CBC (Cipher Block Chaining)

CBC operates by XORing each plaintext block with the previous ciphertext block before encryption, introducing a dependency between blocks. This dependency makes CBC vulnerable to padding oracle attacks, where an attacker can decrypt the ciphertext by exploiting information leaked through padding errors. Additionally, CBC does not provide integrity protection, making it susceptible to tampering attacks.

ECB (Electronic Codebook)

ECB mode encrypts each plaintext block independently, making it vulnerable to patterns in the data. Identical plaintext blocks result in identical ciphertext blocks, which can leak information about the underlying message. ECB should be avoided in most scenarios due to its lack of security guarantees.

Padding Vulnerabilities

Padding schemes are essential for ensuring that the plaintext message is properly aligned with the block size of the cipher algorithm. However, improper padding schemes can introduce vulnerabilities. For example, using padding with CBC mode can expose the encrypted message to padding oracle attacks, as mentioned earlier.

Choosing Secure Cipher Modes

To mitigate the risks associated with weak cipher modes and padding vulnerabilities, it's crucial to opt for stronger alternatives. One such option is the Galois/Counter Mode (GCM), which provides both confidentiality and integrity protection.

GCM (Galois/Counter Mode)

GCM is a mode of operation for symmetric key cryptographic block ciphers. It combines the Counter (CTR) mode of encryption with a universal hash function for authenticated encryption and data authenticity. GCM is generally considered more computationally efficient than CBC, especially for encryption, and provides built-in integrity protection, making it resistant to tampering attacks.

Computational Analysis: AES-GCM vs. AES-CBC

A benchmark comparison between AES-GCM and AES-CBC reveals the computational efficiency of GCM over CBC, particularly for encryption tasks. GCM's parallelizable nature allows for faster encryption compared to CBC, which requires sequential decryption due to its block dependency.

Conclusion

When it comes to securing your data through encryption in Java, choosing the right cipher algorithm and mode is paramount. By steering clear of weak cipher modes like CBC and ECB, and opting for stronger alternatives like GCM, you can bolster the security of your application and safeguard against potential vulnerabilities. Remember, encryption is only as strong as its weakest link – so choose wisely to ensure the confidentiality and integrity of your sensitive data.

The Random Conundrum

In our project, we initially relied on creating multiple instances of Random() for different methods. While this approach seemed straightforward, it came with its own set of drawbacks. Firstly, generating separate instances of Random() for each method proved to be inefficient. Secondly, and perhaps more critically, the randomness produced by Random() was not considered cryptographically secure. This meant that the generated values were susceptible to prediction or manipulation, rendering them unsuitable for security-sensitive tasks such as encryption or password generation.

Addressing the Issues

Recognizing these concerns, we made significant changes to our approach:

1. Static Final Object of Random: Instead of creating multiple instances of Random() scattered across different methods, we opted for a static final object of Random within each class. This not only streamlined our code but also improved its efficiency by reusing the same instance throughout the class.

2. Switching to SecureRandom(): To bolster the security of our random number generation, we made the switch to SecureRandom(). Unlike its conventional counterpart, SecureRandom() offers cryptographic security, making it ideal for applications where randomness plays a crucial role in safeguarding sensitive information.

The SecureRandom Advantage

What sets SecureRandom() apart from Random() is its adherence to cryptographic standards. Here's why it's the preferred choice for security-sensitive scenarios:

• Thread Safety: SecureRandom() is inherently thread-safe, ensuring that concurrent access to the random number generator does not compromise its integrity.

• Use of Unpredictable Sources: Unlike Random(), which relies on a predictable algorithm for random number generation, SecureRandom() utilizes more unpredictable sources such as system events and keyboard timings. This makes it significantly harder for adversaries to predict or manipulate the generated sequences.

• Native PRNG Integration: SecureRandom() leverages native pseudo-random number generators (PRNGs), further enhancing the randomness and security of the generated values.

Conclusion

In the realm of Java development, the choice between Random() and SecureRandom() boils down to the specific requirements of your application. While Random() may suffice for non-security critical tasks, SecureRandom() emerges as the clear winner when it comes to protecting sensitive data from potential threats. By adopting SecureRandom() and implementing best practices for random number generation, you can fortify your application's security posture and mitigate the risks associated with predictable randomness.

Next time you find yourself in need of random number generation in Java, remember the importance of choosing the right tool for the job. Whether it's for encryption, authentication, or any other security-sensitive operation, let SecureRandom() be your trusted ally in the battle against cyber threats.

Online Assessment Round

The first round was the online assessment round. It was a two-hour long test. There were 2 coding questions and around 15-16 MCQ problems. MCQ was related to CS fundamentals, programming language, time complexity, SQL query, English proficiency, etc. The first coding question was related to strings. I was able to solve using brute force and around 11/15 test cases were passed. Probably it was supposed to be solved using the KMP algorithm. The second question was a standard DP knapsack problem: Two arrays are given, presentStockPrice, futureStockPrice you need to maximize the profit given a budget. I was able to pass all the test cases.

Interview Round #1

Out of 100 students, 25 were shortlisted for the interview rounds. The interview started with my introduction, interviewer also introduced himself. He asked me about my projects. There were some questions asked related to my tech stack :

1. Why have you opted for the MERN stack?

2. What are the advantages of MERN over other alternatives?

3. What differences did you see when you used react instead of vanila JS for front end?

4. Why have you opted for MongoDB for your project?

5. What type of schema your project has : Structured or Unstructured?

6. What is horizontal and vertical scaling?

7. Why haven’t you used SQLite etc for your project when your schema is structured?

After project discussion he started with OOPS concept. He asked literally everything A to Z about OOPS in C++. Starting from basic definition, four pillars of OOPS, their classification, real world examples etc. Later he asked me to write code for Operator overloading for binary addition operator to use as String concatenation operator for a class. I wrote the code successfully. Then he start giving some various cases where multiple classes are inheriting from each other, he asked about sequence of constructor calling if we create an object of last descendant class. After that he asked same thing for destructor calling. Later asked about can we pass an object as argument in a function. He asked me to write code for runtime polymorphism. Asked about virtual function, friend function, static variable, function. Overall there was solid grilling on OOPS concept.

After OOPS, he gave me a DSA problem : Given a singly linked list head return the k-th node from the reverse. I wrote the code using brute force in which I first calculated the length and then traversed len-k nodes. But he asked me to write code using one pass. I tried with two pointers method but couldn’t complete it.

He also asked some time complexity related question like insertion and deletion in stack, search in Binary Search tree. Asked about Quick sort complexity and code but I didn’t know the code for this algorithm. After this he asked me a puzzle Two wire puzzle GFG . I tried for around 10 minutes but couldn’t come up with exact solutions. He also helped me but I wasn’t able to come up with exact logic.

Finally the interview ended with followup question from my end about financial learning from working at ION. Overall the interview lasted for around 75 minutes.

Verdict : I was not shortlisted for next round.

For other candidates there were 2 more round online and 3 rounds held at ION Noida campus. All rounds were non technical kind of. They asked about case studies, project discussion, behavioural questions etc.

Tip: Know everything about OOPS, GFG top puzzles and your projects.

Thanks for visiting my blog!

I Applied through the placement cell. After the application, there was a coding round. After the coding round 21 students were shortlisted out of 217. After the interview round 11 Students were finally selected for the internship offer. I couldn’t clear the final round

Why rejected for the role?

I was rejected because I was not able to answer a few questions properly. I answered 1-2 questions totally wrong.

Preparation

• Duration: 6 monthsn

• Topics: DSA, Algorithms, Javascript, React, Express, MongoDB

Tips

1. Learn DSA properly

2. Keep revising DSA and grind daily on leetcode

3. Have in-depth knowledge of resumes and project

4. Don’t mention anything which you are not sure about.

5. A half-filled resume is better than unnecessary topics which you don’t know.

Process

• On Campus

• Eligibility: 6 CGPA

• Resume tip

Round #1 : Online Coding Test

There were 2 sections 1 hour each. The first section consists of two easy problems. The second section had 1 medium and 1 hard problem.

One of the questions was just some variation of the Rotate array by K toward the left. We need to find the number of left rotations to made so the minimum element of the array comes at the zeroth index.

The Second question was just to find the maximum depth of the generic tree (Basically an acyclic graph was given)

The third question was a variation of the Diameter of a generic tree/ graph problem.
The fourth problem was a hard DP problem something related to cities and their happiness index, I think no one was able to solve this problem completely.

Students who were able to solve 3/4 problems were shortlisted for the next round.

Round #2 : Face to Face Interview

There was a panel of 4 members, 3 of them asked me questions. The interview lasted for around 20 minutes.

1. What is an API?

2. Why have you chosen the MERN stack?

3. Data Structure vs Database.

4. Can we create our own API?

5. What are the disadvantages of Virtual DOM? (Didn’t know at all) The answer is too much memory consumption

6. Why have you used MongoDB?

7. I was not clear at all with Database concepts, so much confusion.

8. I was not knowledgeable about SQL.

9. Why have you used Material UI? What is it? it’s alternatives (Ant design, I mispronounced it).

10. How much time did you save using Material UI?

11. Why have you chosen React.Js for your project? What would have you used if not React?

Reference Material

You may refer to my github repository where I usually update any tech interview related material.

Thanks for reading!

People believe in Social Validation a lot, they are ready to manipulate their very own self made perspective about this place called world. For example, someone love to study Humanities or let say s/he like sports and that person has no financial problem to pursue his/her interest as his/her occupation still majority of such folks tend to do what The Society think to be good or great or Elite/respectful/stable/secure etc. But, did you why all this happen ? if we think a little then we will find that we all do this and that kind of things because we have a fear in our subconscious brain, a fear that was preinstalled in our OS for our birth. We all afraid to lose Social Acceptance and so called Society and all of those conservative things. In India people are think much about their children’s marriages more than their careers, their way of thinking, their thought processes etc. kind of intellectual stuffs.

Online Studies

Hello friends, in today's post we are going to talk about "HOW TO USE INTERNET FOR JEE PREPARATION".

Friends as we all know that internet is a great way to get knowledge, get answers of your questions, get resolved your doubts & sometimes entertainment as well :-P ,When it comes to discuss about JEE or NEET Preparation almost every aspirant gets confused about how to use it. So I am here to help you by sharing my experiences.

SO LET'S BEGIN!

Mentorship & Doubt Resolving Platforms

Friends here are a few platforms where you can get real mentorship by great mentors or by those successful aspirants who did great in their attempts.

1. Go IIT- 

                A very good platform for solving your doubts, knowing about best books, discussing about any study's related topics.

       goiit.com

2. Blogs of various JEE toppers or teachers etc. -

      (i) Aman's: blog-  This blog created by Aman Goel   who did secure AIR 33 in JEE ADVANCED 2013.

      Aman's Blog link
         (ii) The blog that you are reading now ;-)
3. Gradeup-
    It's a very good and a free platform for joining a community of JEE aspirants like you.
You will get quizzes, previous year paper and doubt solving platform.

4. Quora :-
   There is lots of profiles of JEE toppers and IITians who are studying in top IITs. You can ask a question to them about preparations and you will get your answers.

Study Resources

Friends please don't believe on those YouTube channels who just give you few and incomplete content and latter-day they will ask you for pay them for videos and all that. There is nothing bad in studying online but in case of you have enrolled in any good national level coaching institute then please don't waste your time on those YouTube channels and just hear to your teacher.

Still there are few good resource for studying online in free and with great quality content.

•   You can use Wikipedia for getting any kind of information in Chemistry or if you are a medical guy then you can use it for Biology also.

• For Mathematics here, a great resource that is Mohit Tyagi Sir's Channel . This is a great work did by Mohit Tyagi sir. You will be got amazed by watching his videos. I have no need to saying anything more about him. Check it yourself

• Any Time Padhai Academy   this one can also useful for you people in Chemistry. But still stick to your teacher in this case.

• Physics Galaxy  is world's best content provider in case of Physics. Physics Galaxy gives you access of complete JEE Physics syllabus video lectures along with Advanced level Illustrations. It provides you lots of more on its website physicsgalaxy.com , you can visit the site and can explore a lot by your own.

Friends here are some channels also available on YouTube but most of them are only upto NCERT level , for JEE ADVANCED you will have need to pay of course, but not in Mathematics because Mohit Tyagi sir is here on YouTube.

Apart from all of these stuff, friends ultimately the thing that will definitely work for you is that your persistence & discipline. Remember internet has lots of destructions so be aware about it and use it wisely.

Thanks for reading

Signing off-

Keshav

Hello friends in this post we will discuss about best books in Chemistry for JEE.

so let's begin!

Friends as most of the JEE aspirants are familiar with this fact that Chemistry has a quiet different nature than remaining two subjects : Physics & Mathematics. So, those guys who think relatively more logical and do believe in understanding and thinking process, find Chemistry tough; they may be good at Physical Chemistry but when it comes to Organic & Inorganic they perform poorly bad and finally ended up with poor rank then what they deserved.

In the same way a 'Chemistry guy' struggles in Physics ( Specially in Mechanics :-) ) and more in Mathematics too.

Friends here we have need to understand that Chemistry is relatively a subject that requires firstly information then understanding and after that, we need to learn application of a few concepts in depth as we people used to do in Mechanics and Calculus etc.

If we start to think that Chemistry is a completely so called ratane vala subject  then it will become very hard to do good in this vast subject.

If you want to feel it in practical way then watch this episode -3 of KOTA FACTORY web series. Link is https://m.youtube.com/watch?v=gIwgSpEg6ZY here.

        By the way as this post is going to tell you about best books then my views will be these:-

• There is no any other good book in market for Chemistry except your standard Class 11th and 12th NCERT TEXTBOOKS Of Chemistry.

• Friends there is a lot Books in market of various publications for Chemistry but believe me they will not going to be help you as much as you think. Those type of books are less a theory kind of book and more an Encyclopedia of Chemistry, so you can stil buy them just for knowing any specific topic in detail.

• But, for Problem Practice the best resource is your coaching sheets and few popular books, as I am going to mention below.

Physical Chemistry

P Bahadur, RC Mukherjee, N Avasthi

I will recommend N Avasthi as a complete JEE oriented Problem book.

Inorganic Chemistry

Nothing needed! Just mug up each and every word of NCERTs. It may sound ridiculous and irritating too, but except chapters like Chemical Bonding and Coordination Chemistry you have to remember everything in IOC.

Organic Chemistry

Here also coaching sheets will be sufficient but still for highly Advanced level Problems I will say go for - MS Chauhan.

      Apart from all of these aspects I will like to tell you guys that in Chemistry your Class Notes and Tricks of your teacher will be best for you.

For those students who are doing Self Study I will highly recommend to purchase good quality video lectures specially for Organic Chemistry.

Thanks for reading.

-signing off

Keshav

Let's begin!

Basic books 

Friends in MATHEMATICS the best material you can get is Sheets or Modules of any renowned national level coaching institute. You can go for any institute like Resonance, Allen, FIITJEE etc.

Books for additional Practice

Again same as Physics here also you can go for two publications- ARIHANT or CENGAGE.

I like both of these equally. But, for little bit more detailed theory you can buy CENGAGE and if you want to above JEE level stuff or little bit out of jee syllabus like in calculus specially, Arihant would be good for you.

Books for your Board Examination

Here you have no need to do anything if you are doing quite well in JEE prep. Remember boards are quite easy, so never afraid to it. Just remember the way of presenting the solution of questions in boards. For this purpose you should only once read NCERT thoroughly.

Friends apart from all these books and study material, there is one thing that you have always need to be remembered that is-

JEE mathematics is it's all about practice, practice and rigorous pracice. Only by practicing lots of GOOD questions in a very consistent manner you can do good in this examination.

I hope this post helped you in finding your books for JEE mathematics.
All the best for your JEE Preparations .
Signing off-
Keshav

Hello, friends today I am going to share with you the biggest hack of JEE prep!

Yes today I am going to tell you about best books for JEE.

Now a days there is a lot of books available in market and online stores that give you content for preparing for the JEE test.

But, it's a very common confusion occurred between students that which book is best for theory, which one should be read for Advanced and which one for Mains and biggest question is that which one will be best for practice.

Coaching students have there own problems because there teacher(s) say them for any particular book and when students could not understand that's one then they buy more books and it's very obvious that they simply got confused between books , and ended up with their worst.

Now let's begin with Physics

PHYSICS

1. The GOD book - 

Concept of Physics (Volume 1 & 2) - by HC Verma.

2. The Most Basic book-

NCERT textbooks of class 11th & 12th

These books will help you for subjective exams also like boards.

3. The book that will be your Guide in the whole journey-

There are two sets of such books, one of them is by CENGAGE Publication and another one is by ARIHANT PRAKASHAN

I will personally recommend you for Cengage .

I have used both books but I found Cengage books by BM Sharma as the best source of all kind of theory, illustrations, questions for JEE Advanced.

Although it contains few printing errors but still it's far better for Advanced than Arihant by DC Pandey.

DC Pandey Books contain less theory and sometimes incomplete too, although they have lots of good questions for problem practice.

3. The Book For Advanced Problem Practice-

Of course without any doubt PROBLEMS IN GENERAL PHYSICS by- IE IRODOV

This is the best book for practicing toughest Problems in JEE Physics.

Go for this when you become quite confident about any particular chapter.

Hope this post will help you in choosing good books for your JEE prep.

Wish you All the Best

Signing off-

Keshav

     Hey friends, Keshav here! I am currently studying at Allen Kota for IIT JEE preparations in class 12th. 

Here on this blog we will share study tips for JEE.

Please share my blog with your friends.