Confusion and Diffusion in Cryptography

confusion

The concept of confusion, as relates to cryptography, was defined in Shannon’s 1948 paper. Generally, this concept attempts to make the relationship between the statistical frequencies of the cipher text and the actual key as complex as possible. Put another way, the relationship between the plain text, cipher text, and …

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Information Entropy

information4

Shannon believed information entropy was a vital subject in information theory. His landmark paper included an entire section entitled “Choice, Uncertainty and Entropy” that rigorously explored this topic. Here we’ll cover just enough about information entropy for you to move forward in your study of cryptography. Entropy has a different …

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The Information Age

information age

You can often hear that we live in the “information age” which obviously makes information theory relevant not only to understanding cryptography, but also to understanding modern society. First, however, we must be clear on what is meant by the phrase “information age.” To a great extent, the information age and …

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Digital Signature

digital signature

An essential purpose of cryptography would be  to ensure nonrepudiation of a delivered message. This is where the receiver of the message cannot deny that the message is genuine. A digital signature is a technique used to help demonstrate this authenticity and the integrity of the message. It is useful for …

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Hybrid Encryption with Integrity

hybrid-encryption

In this article, we will build on the previous hybrid encryption example by adding message integrity. This will mean that, once the encrypted data block has been created, you can check whether or not it has been tampered with or corrupted while in transit to its recipient. Before looking at …

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Hybrid Encryption (RSA+AES)

hybrid-encryption

With RSA you cannot encrypt data that is bigger than the length of the asymmetric key. If you want to encrypt a bigger block of information, what exactly would you do? Preferably, you’d wish to make use of symmetric encryption algorithm such as AES, but the issue you encounter is that …

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Asymmetric Encryption – RSA

rsa

The main problem with symmetric encryption is that of securely sharing keys. For a recipient to decrypt a message, they need the same key as the sender, and this exchange of keys can be very difficult to do securely. A good solution to this problem is to use asymmetric cryptography …

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Advanced Encryption Standard (AES)

AES

The Advanced Encryption Standard (AES) is the latest encryption standard adopted by NIST in 2001 for the symmetric encryption of messages. The AES algorithm was selected as part of a contest to find a replacement for the Data Encryption Standard (DES). This algorithm was based on the Rijndael cipher developed …

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Data Encryption Standard (DES)

encryption

The Data Encryption Standard (DES) used to be the default standard for symmetric encryption of data. DES was based on an earlier design by Horst Feistel and developed by IBM in the early 1970s. DES was submitted to the National Bureau of Standards as part of a drive to propose …

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Symmetric Encryption

encryption

A symmetric encryption algorithm is a two-way encryption procedure that employs the same key for both encryption and decryption of the information. Theoretically, this seems straightforward as both the sender and receiver of the message should know the key, however in practice safely sharing a key is very hard to …

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