The more popular and widely adopted symmetric encryption algorithm likely to be encountered nowadays is the Advanced Encryption Standard (AES). It is found at least six time faster than triple DES. A replacement for DES was needed as its key size was too small. With increasing computing power, it was considered vulnerable against exhaustive key… Continue reading Advanced Encryption Standard
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Triple DES
The speed of exhaustive key searches against DES after 1990 began to cause discomfort amongst users of DES. However, users did not want to replace DES as it takes an enormous amount of time and money to change encryption algorithms that are widely adopted and embedded in large security architectures. The pragmatic approach was not… Continue reading Triple DES
Key Generation
The round-key generator creates sixteen 48-bit keys out of a 56-bit cipher key. The process of key generation is depicted in the following illustration − The logic for Parity drop, shifting, and Compression P-box is given in the DES description. DES Analysis The DES satisfies both the desired properties of block cipher. These two properties… Continue reading Key Generation
Round Function
The heart of this cipher is the DES function, f. The DES function applies a 48-bit key to the rightmost 32 bits to produce a 32-bit output.
Data Encryption Standard
The Data Encryption Standard (DES) is a symmetric-key block cipher published by the National Institute of Standards and Technology (NIST). DES is an implementation of a Feistel Cipher. It uses 16 round Feistel structure. The block size is 64-bit. Though, key length is 64-bit, DES has an effective key length of 56 bits, since 8… Continue reading Data Encryption Standard
Feistel Block Cipher
Feistel Cipher is not a specific scheme of block cipher. It is a design model from which many different block ciphers are derived. DES is just one example of a Feistel Cipher. A cryptographic system based on Feistel cipher structure uses the same algorithm for both encryption and decryption. Encryption Process The encryption process uses… Continue reading Feistel Block Cipher
Block Cipher
The basic scheme of a block cipher is depicted as follows − A block cipher takes a block of plaintext bits and generates a block of ciphertext bits, generally of same size. The size of block is fixed in the given scheme. The choice of block size does not directly affect to the strength of… Continue reading Block Cipher
Modern Symmetric Key Encryption
Digital data is represented in strings of binary digits (bits) unlike alphabets. Modern cryptosystems need to process this binary strings to convert in to another binary string. Based on how these binary strings are processed, a symmetric encryption schemes can be classified in to − Block Ciphers In this scheme, the plain binary text is… Continue reading Modern Symmetric Key Encryption
Security Value
Vigenere Cipher was designed by tweaking the standard Caesar cipher to reduce the effectiveness of cryptanalysis on the ciphertext and make a cryptosystem more robust. It is significantly more secure than a regular Caesar Cipher. In the history, it was regularly used for protecting sensitive political and military information. It was referred to as the unbreakable cipher due… Continue reading Security Value
Security Value
It is also a substitution cipher and is difficult to break compared to the simple substitution cipher. As in case of substitution cipher, cryptanalysis is possible on the Playfair cipher as well, however it would be against 625 possible pairs of letters (25×25 alphabets) instead of 26 different possible alphabets. The Playfair cipher was used… Continue reading Security Value