Theory of Cryptography

Introduction to Cryptography

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Introduction to ciphers, that is a short history of the first encryption means and the basic principles of modern cryptography.

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Kerckhoffs's Principle

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The Kerckhoffs's principle is one of the most basic and most important principles of modern cryptography. It was first published in 1883 in France.

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Steganography is a way of securing data, by simply hiding it. Learn its history and the various methods that are used at present.

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Protocol are sets of actions that should be performed in order to accomplish the goals. They are essential in almost all cryptographic operations.

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TCP/IP Protocols

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TCP/IP protocols are probably the most popular protocols used in computer networks. Learn how to build and process TCP/IP messages in different layers of the network.

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Application Protocols

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Application layer protocols operate in the highest layer of the network model. They create interfaces available to applications.

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Notation of Numbers

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Notation of numbers are ways of representing the numbers. They are necessary for all further mathematical operations.

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Binary Numbers

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Binary numbers are used by all computers all around the world. Learn the most popular binary systems and the most common mathematical operations.

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Time Estimation

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Time estimation of basic mathematical operations is necessary for assessing and improving the quality of computer algorithms.

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Modular Arithmetic

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Modular arithmetic is a system of arithmetic for integers, where values reset to 0 after reaching a certain predefined value. It is necessary to asymmetric encryption algorithms.

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Security of Ciphers

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Assessing cipher quality: Perfect Security and Semantic Security definitions, descriptions, and examples.

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Padding standards are mechanisms for appending some predefined values to messages. They are required by many algorithms, including block symmetric ciphers.

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Block Ciphers Modes

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Using various modes of operation of block ciphers allow to operat on large data streams, without the risk of compromising the provided security.

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Pseudorandom Generator

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Pseudorandom generators (PRG) are used to create random sequences of numbers in deterministic devices. They are extremely important elements of all cryptosystems.

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Pseudorandom Functions

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Pseudorandom functions and permutations produce pseudorandom data indistinguishable from random sequences. They are used in many cryptographic algorithms.

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One-way Function

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One-way functions are easy to compute but it is very difficult to compute the value of their inverse functions.

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Message authentication code (MAC) algorithms are used for authentication and verification of received messages.

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Password-based encryption (PBE) algorithms are mechanisms that allow users to create strong and secure secret keys.

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Software Signing

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Software signing is used for providing application authorization and preventing any unauthorised modifications of their source code.

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Index of Coincidence

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The index of coincidence (IC) shows how likely is the situation that during comparing two texts letter by letter, two currently compared letters are the same.

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