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.
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.
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.
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.
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).
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.
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.
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.
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.
2016-05-09 | #os-dev #programming
Buddy memory allocator is a memory management technique that divides memory into fixed-size blocks and allocates them based on power-of-2 sizes, allowing efficient allocation and deallocation with minimal fragmentation. Introduction At any point in time, the memory consists of a collection of blocks of consecutive memory, each of which is a size of a power of two.
