Aes on Aditya Telange
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Hugo -- 0.134.3en2020 - 2024 Aditya TelangeFri, 20 May 2022 00:00:00 +0530Cryptohack - Keyed Permutations [5 pts]
https://adityatelange.in/writeups/cryptohack/aes/keyed-permutations/
Fri, 20 May 2022 00:00:00 +0530https://adityatelange.in/writeups/cryptohack/aes/keyed-permutations/<blockquote>
<p>The Solution is shared considering <a href="https://cryptohack.org/faq/#solutions">CAN I SHARE MY SOLUTIONS?</a></p>
</blockquote>
<h2 id="problem">Problem</h2>
<p>AES, like all good block ciphers, performs a “keyed permutation”. This means that it maps every possible input block to a unique output block, with a key determining which permutation to perform.</p>
<blockquote>
<p>A “block” just refers to a fixed number of bits or bytes, which may represent any kind of data. AES processes a block and outputs another block. We’ll be specifically talking the variant of AES which works on 128 bit (16 byte) blocks and a 128 bit key, known as AES-128.</p>Cryptohack - Resisting Bruteforce [10 pts]
https://adityatelange.in/writeups/cryptohack/aes/resisting-bruteforce/
Fri, 20 May 2022 00:00:00 +0530https://adityatelange.in/writeups/cryptohack/aes/resisting-bruteforce/<blockquote>
<p>The Solution is shared considering <a href="https://cryptohack.org/faq/#solutions">CAN I SHARE MY SOLUTIONS?</a></p>
</blockquote>
<h2 id="problem">Problem</h2>
<p>If a block cipher is secure, there should be no way for an attacker to distinguish the output of AES from a <a href="https://en.wikipedia.org/wiki/Pseudorandom_permutation">random permutation</a> of bits. Furthermore, there should be no better way to undo the permutation than simply bruteforcing every possible key. That’s why academics consider a cipher theoretically “broken” if they can find an attack that takes fewer steps to perform than bruteforcing the key, even if that attack is practically infeasible.</p>