DES (DATA ENCRYPTION STANDARD)

Data Encryption Standard (DES)

is a block cipher algorithm that takes plain text in blocks of 64 bits and converts them to ciphertext using keys of 48 bits. It is a symmetric key algorithm, which means that the same key is used for encrypting and decrypting ​data.

Developed in the early 1970s at IBM and based on an earlier design by Horst Feistel, the algorithm was submitted to the National Bureau of Standards (NBS) following the agency's invitation to propose a candidate for the protection of sensitive, unclassified electronic government data. In 1976, after consultation with the National Security Agency (NSA), the NBS selected a slightly modified version (strengthened against differential cryptanalysis, but weakened against brute-force attacks), which was published as an official Federal Information Processing Standard (FIPS) for the United States in 1977.

The publication of an NSA-approved encryption standard led to its quick international adoption and widespread academic scrutiny. Controversies arose from classified design elements, a relatively short key length of the symmetric-key block cipher design, and the involvement of the NSA, raising suspicions about a backdoor. The S-boxes that had prompted those suspicions were designed by the NSA to remove a backdoor they secretly knew (differential cryptanalysis). However, the NSA also ensured that the key size was drastically reduced so that they could break the cipher by brute force attack.The intense academic scrutiny the algorithm received over time led to the modern understanding of block ciphers and their cryptanalysis

DES is insecure due to the relatively short 56-bit key size. In January 1999, distributed.net and the Electronic Frontier Foundation collaborated to publicly break a DES key in 22 hours and 15 minutes (see chronology). There are also some analytical results which demonstrate theoretical weaknesses in the cipher, although they are infeasible in practice. The algorithm is believed to be practically secure in the form of Triple DES, although there are theoretical attacks. This cipher has been superseded by the Advanced Encryption Standard (AES). DES has been withdrawn as a standard by the National Institute of Standards and Technology.

Electronic Code Book (ECB)

Electronic Code Book (ECB) is a simple mode of operation with a block cipher that's mostly used with symmetric key encryption. It is a straightforward way of processing a series of sequentially listed message blocks.

The input plaintext is broken into numerous blocks. The blocks are individually and independently encrypted (ciphertext) using the encryption key. As a result, each encrypted block can also be decrypted individually. ECB can support a separate encryption key for each block type.

In ECB, each block of plaintext has a defined corresponding ciphertext value, and vice versa. So, identical plaintexts with identical keys always encrypt to identical ciphertexts. This means that if plaintext blocks P1, P2 and so on are encrypted multiple times under the same key, the output ciphertext blocks will always be the same.

In other words, the same plaintext value will always result in the same ciphertext value. This also applies to plaintexts with partial identical portions. For instance, plaintexts containing identical headers of a letter and encrypted with the same key will have partially identical ciphertext portions.

For any given key, a codebook of ciphertexts can be created for all possible plaintext blocks. With the ECB mode, encryption entails only looking up the plaintext(s) and selecting the corresponding ciphertext(s). This operation is like assigning code words in a codebook. In fact, the term "code book" derives from the cryptographic codebooks used during the United States Civil War (1861-1865).

In terms of error correction, any bit errors in a ciphertext block will only affect decryption of that block. Chaining dependency is not an issue. Any reordering of the ciphertext blocks will only reorder the corresponding plaintext blocks. It won't affect decryption.

What are drawbacks of Electronic Code Book?

• ECB uses simple substitution rather than an initialization vector or chaining. These qualities make it easy to implement. However, this is also its biggest drawback. Two identical blocks of plaintext result in two correspondingly identical blocks of ciphertext, making it cryptologically weak.
• ECB is not good to use with small block sizes -- say, for blocks smaller than 40 bits -- and identical encryption modes. In small block sizes some words and phrases may be reused often in the plaintext. This means that the ciphertext may carry (and betray) patterns from the same plaintext, and the same repetitive part-blocks of ciphertext can emerge. When the plaintext patterns are obvious, it creates opportunities for bad actors to guess the patterns and perpetrate a codebook attack.
• ECB security is weak but may be improved by adding random pad bits to each block. Larger blocks (64-bit or more) would likely contain enough unique characteristics (entropy) to make a codebook attack unlikely.

Make a Program DAS ECB Mode Using Python

Before you run this Program, please install the module I used in the program 'pycryptodome'by installing via the terminal by typing

'pip install pycryptodome'

Then press enter

Watch This Video For The Explanation

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