Question

Perform a Web search for “Announcing the Advanced Encryption Standard (AES).” Read this document, which is a FIPS 197 standard. Write a short overview of the development and implementation of this cryptosystem. Your response must include the type of Algorithm used, the size of data blocks that can be processed, and the lengths of the cipher keys.

Answer 1

Answer:-

A cryptosystem is a pair of algorithms: one for the encryption of data and another for decryption. Often these algorithms use a unique key which should be kept secret, in which case the process for generating and sharing the key is also considered part of the cryptosystem.

Modern cryptography is essential to the digital world we live in and has grown to be quite complex. It is used for sending messages in a secure manner on the internet, such as our credit card information and other private data. Encryption is used to keep our data secure online and locally. The Advanced Encryption Standard (AES) is used by governments to maintain the secrecy of their documents and was chosen from a number of candidates across the mathematics community for its security and efficiency.

In addition, digital security can also be used to maintain anonymity, to authenticate one’s identity via digital signatures, to demonstrate proof of work in blockchain technologies and to ensure that software and messages are free from tampering.

A cryptosystem is a pair of algorithms: one for the encryption of data and another for decryption. Often these algorithms use a unique key which should be kept secret, in which case the process for generating and sharing the key is also considered part of the cryptosystem.

Modern cryptography is essential to the digital world we live in and has grown to be quite complex. It is used for sending messages in a secure manner on the internet, such as our credit card information and other private data. Encryption is used to keep our data secure online and locally. The Advanced Encryption Standard (AES) is used by governments to maintain the secrecy of their documents and was chosen from a number of candidates across the mathematics community for its security and efficiency.

In addition, digital security can also be used to maintain anonymity, to authenticate one’s identity via digital signatures, to demonstrate proof of work in blockchain technologies and to ensure that software and messages are free from tampering.

Definitions
Cryptography terms
Here are a few definitions of some terms relating to cryptography and cryptosystems:

Plaintext: The original message in its original legible form.
Ciphertext: Encrypted text that will appear to be a random string.
Encryption: The process of converting data into its cryptic form that prevents unauthorized access, i.e. converting plaintext to ciphertext. This process requires encryption keys which provide information regarding the specific implementation of a given encryption algorithm.
Decryption: The process of converting encrypted data back into its original form for use, i.e. converting ciphertext back to plaintext. Decryption requires a decryption key which provides the specific information required to ‘undo’ the encryption.
Symmetric Key Cryptosystems: Cryptosystems that use the same key for encryption as well as decryption. This key is assumed to be a shared secret between the two parties exchanging messages. A few examples of Symmetric Key Cryptosystems:
Cipher: A system of encryption that maps each character to a substitute.
Code: A system of encryption that maps each word or feature to a substitute.
Shift Cipher: A cipher that replaces each character with another chosen by moving forwards through the alphabet by some fixed shift factor.
Asymmetric or Public Key Cryptosystems: Cryptosystems that use public-private key pairs. This enables anyone to encrypt messages for sending to the publisher of the keys (using the public key) but only the holder of the private key will be able to decrypt the messages.
Digital Signatures: A digital code (generated and authenticated by public key encryption) which is attached to an electronically transmitted document to verify its contents and the sender's identity.
Number theory terms
The following are some important concepts required for cryptography from the field of number theory

Modulo: The remainder operator (e.g. 17 modulo 5 is 2, i.e. 17 when divided by 5 leaves a remainder of 2). This is often shortened to mod, we write 17 ≡ 2 (mod 5), read as "17 is congruent to 2, modulo 5".
Coprime: In number theory two values are said to be coprime or relatively prime if they do not share any common prime factors. That’s to say that their greatest common divisor (GCD) or highest common factor is 1.
Characters
It is general practice in cryptography to follow the standards of Rivest, Shamir and Adleman, the inventors of the RSA encryption algorithm, by using Alice and Bob as the main protagonists in any example of cryptosystem protocols. In examples of attacks, Eve is usually cast as the attacker. That is, Alice wants to send messages privately to Bob, and Eve is trying to spy on the messages.

Design Objectives & Goals
The design objectives of a cryptosystem can be summarized by Kerckhoff’s Priniciple:

The system must be secure even if everything except the private key is public information. In particular, the design of the system must not be required to be kept secret.
This is the approach taken by modern cryptography (as compared to earlier cryptographic systems, which often relied on obscurity, i.e. aiming for security by keeping the system or parts of it secret or unclear.)

Beyond security computational efficiency and the practicality of implementation are sub-objectives in cryptosystem design. This is shown in the development of AES whereby the US Government accepted suggestions for algorithms and 15 made it to the final. Some of the finalists were more secure than the ultimate winner but were dismissed for requiring too much processing power.

The trade-off between complexity and therefore security and ease of implementation can be further seen in the guidance for the use of AES encryption. Top secret information is encrypted using a 192 or 256 bit key whereas less highly classified information may be encrypted using a 128-bit key for efficiency. AES involves 10 rounds of encryption processes for 128-bit keys, 12 rounds for 192-bit keys and 14 rounds for 256-bit keys.