## VII. Asymmetric Cryptography: Overview

Invention -Asymmetric Key Cryptography The main idea on the development of Asymmetric Key Cryptography, was to avoid two problems, key distribution and digital signatures. Although it was first discovered by M. J. Williamson who worked under GCHQ, his work was kept secret. Few years later, it was first published by W. Diffie and M. Hellman … Continue reading VII. Asymmetric Cryptography: Overview

## VI. Operation Modes For Block Ciphers

Why there are Operation Modes for Block Ciphers ? Simply, operation modes are methods that allow the safe use of a block of passwords under a single key. They were created specifically for use in encryption and authentication. Although they are associated with symmetric cryptography, in theory, they can also be used in public key … Continue reading VI. Operation Modes For Block Ciphers

## DES Python Script

To use below python code, copy & paste to any text editor (e.g. Sublime Text) as a python file. Then, all you need to do is to run on your command line or terminal (Pyhton3 needs to be installed). Have Fun ! #DataEncryptionStandard Encryption Protocol Python(3.6) Implementation by otapsin for CryptoQuantus. #Adapted from, ""https://academic.csuohio.edu/yuc/security/Chapter_06_Data_Encription_Standard.pdf"" #Initial … Continue reading DES Python Script

## V. 2,3-DES & AES

2-DES (Double) Double-DES has two different encryption phases with two different keys (K_1, K_2) such that: Ciphertext (Encryption): Enc (K2, Enc(K1, P)) Plaintext (Decryption): Dec(K1, Dec(K2, C)) Meet in the Middle Attack Meet-in-the-middle is a known plaintext attack, that targets block cipher cryptographic functions, relies on exponentially reducing the number of brute force permutations required to … Continue reading V. 2,3-DES & AES

## IV. Block Cipher & DES

Before getting started with Block Cipher, digital computer communications based on bits, where 1 byte equals 8 bits. For instance, the word cryptoquantus consist of 13 characters (byte), so it equals to 8x13 = 104 bits . ASCII (American Standard Code for Information Interchange) is an encoding representing each typed character by a number, where … Continue reading IV. Block Cipher & DES

## III. Transposition Cipher

First Transposition Cipher in History It was firstly used by Greeks and Spartans for military secrecy, 15th Century B.C. as Scytale Cipher. A Scytale Cipher is simply a wooden stick around which a strip of leather is wrapped. Sender writes the message along the length of the stick and unwinds the strip, where letters are … Continue reading III. Transposition Cipher

## II. Information Entropy & Cryptography (Brute Force and Cryptanalysis)

Brute Force Attack As the name suggests, "Brute Force Attack", the process is based on testing all possible keys until find the correct key. Let's consider that the attacker finds out the correct key after trials. We have 4 keys such as, k_1-(00), k_2-(01), k_3-(10), k_4-(11) where information entropy of the system is 2 bits … Continue reading II. Information Entropy & Cryptography (Brute Force and Cryptanalysis)

## I. Cryptography: 101

Cryptography Terminology Cryptography, the study of encryption and decryption techniques. Cryptanalysis, codebreaking and deciphering ciphertext without the key. Cryptology, the field of cryptography and cryptology. Alice, Bob & Eve Framework Alice sends a message to Bob and Eve (stands for eaves dropper) wants to get the message. Here; there are, classical (e.g. Caesar cipher) and modern … Continue reading I. Cryptography: 101