Topics covered: Cyclic Groups Discrete Logarithm Problem Applications Attacks on DLP Brute Force Attack on DLP Baby Step Giant Step Algorithm CTF Challenges based on DLP Prerequisites: Mathematical Structures Cyclic Groups Abelian Groups in which all the elements can be produced using a single element in the group. This element is known as a generator... Continue Reading →

# Finite Fields- Number Theory

This blog post covers one of the most important Mathematical Structures for Cryptography- Fields. It is used in both Symmetric and Asymmetric key Cryptography. This blog post gives a basic introduction to Finite Fields and arithmetic operations on it, but I hope the purpose of it is served- to make people, who don't have basic knowledge... Continue Reading →

# ASIS Finals CTF 2017- Gracias Writeup

Points: 287 Solves: 9 Category: Crypto Description: Some people think that combination of cryptographic systems will definitely improve the security. That's your turn to prove them wrong. This challenge is a bit simpler than it looks like. It is a multi-prime RSA challenge where we are given an encryption script, which has two functions, one... Continue Reading →

# Blinding Attack on RSA Digital Signatures

This blog primarily focuses on Blinding Attack- an elementary vulnerability in RSA cryptosystem used to forge Digital Signatures. The working and properties of Digital Signatures will be described before directly jumping onto the attack. In the end, we discuss ways to prevent this attack. Digital Signature using RSA RSA is a kind of "Trapdoor One-way... Continue Reading →

# Polynomial Interpolation

I have been reading "How to Share a Secret" in detail for the past few weeks, a revolutionary research paper by Adi Shamir. This paper applies some of the concepts of Number Theory and Algebra, one of which is polynomial interpolation, and has been used to construct a secure and reliable key management system. The... Continue Reading →

# CBC Bit-Flipping Attack

In this blog post, the attack on CBC mode of block cipher encryption will be discussed and in the end, detailed writeup for the 16th challenge of Matasano-Crypto-Challenge i.e. about the Bit Flipping Attack in AES-CBC will be provided with explanation! I want the reader to go through these concepts discussed in the following blog... Continue Reading →

# Block-size Detection

In the previous blog, "Detecting the mode of block cipher being used" was discussed. In this blog, the second step in the attacking of a block cipher i.e. detecting the block size of the cipher, will be discussed. Link to the implementation script has been given at the end of this post which is written... Continue Reading →

# AES Mode Detection Oracle

In a series of blogs, attacks on AES- Advanced Encryption Standard, will be discussed. There are a number of steps involved to break a block cipher (AES being one of them): Recognizing the mode of block cipher being used. Finding the size of the block being used in the block cipher. Implementing a suitable attack... Continue Reading →

# A Tale of Resurrection

"It is difficult to fight against anger, for a man will buy revenge with his soul" This is a tale of resurrection. Resurrection, not of any human soul or body, but resurrection of ideas. Ideas that still have the potential to petrify every human present on this planet. It has often been observed that terrorist... Continue Reading →