## Fermat's Little Theorem and Euler's Theorem

2017-07-23 | #mathematics #number-theory

Fermat’s Little Theorem, a precursor to Euler’s, provides a simple yet powerful relationship between prime numbers and modular exponentiation. Euler’s Theorem generalizes this relationship to all integers, offering a broader perspective on modular arithmetic.

## GPG Essentials

2017-07-05 | #cryptography #tooling

Introduction GnuPG is a hybrid-encryption software program because it uses a combination of conventional symmetric-key cryptography for speed, and public-key cryptography for ease of secure key exchange, typically by using the recipient’s public key to encrypt a session key which is used only once.

## The Monty Hall Problem

2017-07-05 | #probability

The Monty Hall problem is a counter-intuitive statistics puzzle loosely based on the American television game show Let’s Make a Deal and named after its original host, Monty Hall. The Game There are three doors, behind which are two goats and a car; You randomly pick a door; Monty, examines the other two doors and always opens one of them with a goat.

## Classical Ciphers

2017-05-26 | #cryptography #history

All modern ciphers are based on some kind of substitution operation. A block of bits is substituted with another block of bits according to a given table or algorithm. Monoalphabetic cipher: the same element in the plaintext alphabet is always encrypted to the same element in the ciphertext alphabet.

## Euclidean Algorithm

2017-04-16 | #mathematics #number-theory

A fundamental and efficient algorithm to compute the greatest common divisor (gcd) of two integer numbers. Given two integers a and b, the algorithm comes in two flavors: basic: yields the gcd(a,b); extended: yields two integers x and y such that gcd(a,b) = a·x + b·y As a notational shortcut from now on we’ll write (a,b) instead of gcd(a, b).

## Abstract Syntax Notation 1

2017-03-02 | #encoding #standards

ASN.1 is a standard notation syntax defined in ITU-T X.680 to describe rules and structures for representing data in telecommunications and computer networking. ASN.1 itself does not mandate any encoding or parsing rules, but usually ASN.

## AT Commands Reference

2016-11-26 | #communications #standards

The Hayes command set, also called the AT command set, is a specific command language originally developed by Dennis Hayes[1] for the Hayes Smartmodem 300 baud modem in 1981. The command set consists of a series of short text strings which can be combined to produce commands for operations such as dialing, hanging up, and changing the parameters of the connection.

## Bash Shortcuts

2016-08-02 | #bash #tooling

The bash shell has a very rich set of convenient shortcuts. This ability to edit the command line is provided by the GNU Readline library. Readline keybindings are taken from the Emacs text editor.

## The Mighty Unix History

2016-06-02 | #history #unix

UNIX is a family of operating systems that derive from the original AT&T UNIX, developed in the 1970s at the Bell Labs research center by Ken Thompson and Dennis Ritchie.