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<!doctype html>
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<div class="p-4 mb-4 text-light bg-dark rounded pt-5 ps-5">
<h1 class="fst-italic text-center text-decoration-underline mt-2">Capture The Flag blog</h1>
<img src="crypto1.png" class="img-fluid mt-3" style="width: auto; height: auto;"
alt="Competitive Programming">
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From RetroCoders
</h3>
<article class="blog-post">
<h2 class="blog-post-title">Cryptograhy Blog</h2>
<p class="blog-post-meta">July 26, 2021 by <a href="#" class="text-success">farhan</a></p>
<p class="fs-5">As the blog's name suggesting, Cryptography is an encryption or decryption of data
over the
internet/ local server. Cryptography is a big part in networking and security. So, the question
is, "did it also important for CTF?" The answer is YES. Cryptography is also play a very
important role in CTFs as they have seperate question type in CTF.</p>
<img src="crypto2.jpeg" class="img-fluid" style="width: auto; height: auto;" alt="Blogs">
<h2 class="blog-post-title mt-2"> What is Cryptograhy?</h2>
<p class="fs-5">As I explained above, Cryptography is an encryption or decryption of data over a network. Let me
explain the mechanism of cryptography - </p>
<ul>
<p class="fs-5">Taking a example of whatsapp, when you (means client) send a message to your friend (means
another client). Firstly, message get encoded by using some algorithms and then pass over the
whatsapp's network with your IP address and encrypted message and some more little
information which are required. When the message is received by your friend, the message
then decrypted and
show the message on whatsapp with your number.</p>
</ul>
<p class="fs-5">This is an example that how cryptography works. NOTE - if someone get your encrypted message
using spoofing or packet capturing, then he/she can also decode the message using the algorithm
use by whatsapp. Well for your information, whatsapp using <strong> Curve25519</strong>
algorithm for encrptyion. How i know this? Salute to google search.</p>
<h2 class="blog-post-title mt-2">Types of Cryptograhy</h2>
<p class="fs-5">Cryptograhy is mainly divided in three types -
<ol>
<li class="fs-5"><strong>Symmetric Key Cryptography -</strong> In this type of cryptography, Sender and
reciever have a same key for encryption or decryption of data. The key is kind of password
through which it is encrpyted or decrpyted. So , the key over the encrpytion is same on both
side. Some examples are RC4, AES, DES, etc.</li>
<li class="fs-5"><strong>Hashing Cryptography -</strong> Hashing is a method of cryptography that converts any
form of data into a unique string of text. Any piece of data can be hashed, no matter its
size, type, length, the hash that any data produces is always of same length. Hashing
techniques are very common these days for encrpytion of data even whatsapp, email, and many
other companies using it. Some examples are MD5, #SHA-1, #SHA-256, #SHA-512, etc. Hashing is
also used in <strong> Cryptocurrency</strong>.</li>
<li class="fs-5"><strong>Asymmetric Key Cryptography -</strong> Asymmetric Cryptography is also known as public
key cryptography. In this method, there are two keys for encrpytion and decrpytion. The data
is encypted with some key and decrpyted using some other key. That's why, This algorithm is
better then symmetric algorithm but its speed of encrpytion and decrpytion is slow then
symmetric algorithm.</li>
</ol>
</p>
<img src="crypto3.png" class="img-fluid" style="width: auto; height: auto;" alt="Blogs">
<h2 class="blog-post-title mt-2">Tools For Cryptography</h2>
<p class="fs-5">There are many tools for cryptography in kali linux or on internet for use in CTF - </p>
<ul>
<li><strong>John the ripper toolkit</strong></li>
<li><strong>Hydra toolkit</strong></li>
<li><strong>hashcat tool</strong></li>
<li><strong>Johnny (GUI interface of John the ripper)</strong></li>
</ul>
<p class="fs-5">There are many other tools but I think this much is sufficient.</p>
<h2 class="blog-post-title mt-2">References</h2>
<p class="fs-5">I think the above introduction of cryptography is sufficient for your understanding. I am also
providing some links regarding cryptography for better understanding through writeups.</p>
<!--p><strong>Tips And Tricks :</strong> </p-->
<strong class="fs-5">References:</strong>
<ul>
<li><a href="https://github.com/DownUnderCTF/Challenges_2020_public/tree/master/crypto/rot-i"
class="text-success">ROT-i</a> : <a
href="https://github.com/DownUnderCTF/Challenges_2020_public/blob/master/crypto/rot-i/exploit/writeup.md">
Writeup by DownUnderCTF</a></li>
<li><a href="https://github.com/DownUnderCTF/Challenges_2020_public/tree/master/crypto/extra-cool-block-chaining"
class="text-success">Extra Cool Block Chaining</a> : <a
href="https://github.com/DownUnderCTF/Challenges_2020_public/blob/master/crypto/extra-cool-block-chaining/exploit/writeup.md">
Writeup by DownUnderCTF</a></li>
<li><a href="https://github.com/kevinjycui/picoCTF-2019-writeup/blob/master/Cryptography/Flags/README.md"
class="text-success">Flags</a> : <a
href="https://github.com/kevinjycui/picoCTF-2019-writeup/blob/master/Cryptography/Flags/README.md">
Writeup by kevinjycui</a></li>
</ul>
</p>
<h2 class="blog-post-title">Final Words</h2>
<p class="fs-5">Cryptography is not a small topic. If you go in depth, you find that cryptography is basically
involve in everything and in every question.</p>
</article>
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<h4 class="fst-italic">Quote Of The Day</h4>
<p class="mb-0">"Privacy is an inherent human right, and a requirement for maintaining the human
condition with dignity and respect."<strong> - Bruce Schneier</strong></p>
</div>
<!--div class="p-4 mb-3 bg-black rounded mt-3 ">
<h4 class="fst-italic">Need Help?</h4>
<p class="mb-0">I have a written a blog for Competitive Programming on this website. It will provide you1
basic building blocks and some tips and tricks.
<a href="blog1.html"> Try this out</a> or you can message me on github for any kind of question.
</p>
</div-->
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