Cryptography for the Everyday Developer

This is an article in a series on Cryptography for the Everyday Developer. Follow along to learn the basics of modern cryptography and encryption. The Data Encryption Standard (DES) is based upon the principles of a substitution-permutation network that we learned about in the last post in this series. The design of DES is based on the principles of Feistel ciphers, which are a particular configuration of a substitution-permutation network developed by Horst Feistel at IBM. ...

This is an article in a series on Cryptography for the Everyday Developer. Follow along to learn the basics of modern cryptography and encryption. A block cipher is a type if cipher that combines an encryption/decryption algorithm that works on blocks of data with a mode of operation that details the techniques to process sequences of data blocks. While many different block cipher algorithms exist, they all share a common structural design: they apply a series of transformations — known as rounds — that iteratively manipulate the input data. These rounds consist of small, repeatable operations that gradually transform the plaintext into ciphertext. ...

This is the fifth article in a series on Cryptography for the Everyday Developer. Follow along to learn the basics of modern cryptography and encryption. When discussing encryption, you’ll often hear talk about the strength of a security system as measured in “bits.” For example, systems might advertise their strength as having 128-bits or 256-bits. But what exactly does security measured in bits mean? Let’s demystify this common yet sometimes misunderstood concept. ...

This is the fourth article in a series on Cryptography for the Everyday Developer. Follow along to learn the basics of modern cryptography and encryption. Modular arithmetic is the foundation for asymmetric cryptography like RSA, elliptic curves, or Diffie-Hellman — all of them rely on the properties of modular arithmetic to guarantee security and secrecy. Since modular arithmetic is so important to cryptography, it pays to understand how it works. This post will help us along the journey by demystifying modular arithmetic, explaining how it works, and why it matters for cryptography. ...

This is the third article in a series on Cryptography for the Everyday Developer. Follow along to learn the basics of modern cryptography and encryption. Without randomness, cryptography would be impossible because all operations would become predictable and therefore insecure. — Jean-Philippe Aumasson, Serious Cryptography The cryptographic strength of most systems lies in their ability to generate random numbers that cannot be easily guessed or reproduced, making it difficult for adversaries to crack the encryption or predict the output. Unfortunately for us, computers and the software that they run are very predictable. As long as they are given the same inputs each time, they’ll always come up with the same outputs. This is very good for reliability, but not so good for cryptography where randomness and unpredictability are required for secure operation. ...

This is the second article in a series on Cryptography for the Everyday Developer. Follow along to learn the basics of modern cryptography and encryption. A cipher is only useful if it is secure. What makes a cipher secure? Let’s remember the use case for classical ciphers — keeping messages confidential. Caesar’s cipher and Vigenère’s cipher both suffer from a similar flaw, which makes them insecure and unusable for secure communication. For both ciphers, the flaw is obvious — these ciphers allow an attacker to learn how the cipher works by inspecting the ciphertext itself. This allows an eavesdropper can decrypt the message given only the ciphertext. A secure cipher, on the other hand, is one where it is not possible to learn anything about the plaintext or the cipher’s behaviour even by inspecting numerous plaintext or ciphertext messages. ...

This is the first article in a series on Cryptography for the Everyday Developer. Follow along to learn the basics of modern cryptography and encryption. The best way to begin learning about encryption is by example. And thankfully, there exist many examples of encryption throughout history that we can draw from. One of the earliest well-known examples of encryption is the Caesar Cipher, and we will begin there. The Caesar cipher is one of the oldest and simplest forms of encryption. It works by shifting each letter in your message a fixed number of positions down the alphabet. For example, with a shift of 3: ...