Question

What is cryptography? Compare and contrast Transposition, Substitution, and Product ciphers with examples

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Answer 1

1.cryptography

Definition: Cryptography is associated with the process of converting ordinary plain text into unintelligible text and vice-versa. It is a method of storing and transmitting data in a particular form so that only those for whom it is intended can read and process it. Cryptography not only protects data from theft or alteration, but can also be used for user authentication.

Description: Earlier cryptography was effectively synonymous with encryption but nowadays cryptography is mainly based on mathematical theory and computer science practice.

Modern cryptography concerns with:

Confidentiality - Information cannot be understood by anyone

Integrity - Information cannot be altered.

Non-repudiation - Sender cannot deny his/her intentions in the transmission of the information at a later stage

Authentication - Sender and receiver can confirm each

Cryptography is used in many applications like banking transactions cards, computer passwords, and e- commerce transactions.

Three types of cryptographic techniques used in general.

1. Symmetric-key cryptography

2. Hash functions.

3. Public-key cryptography

Symmetric-key Cryptography: Both the sender and receiver share a single key. The sender uses this key to encrypt plaintext and send the cipher text to the receiver. On the other side the receiver applies the same key to decrypt the message and recover the plain text.

Public-Key Cryptography: This is the most revolutionary concept in the last 300-400 years. In Public-Key Cryptography two related keys (public and private key) are used. Public key may be freely distributed, while its paired private key, remains a secret. The public key is used for encryption and for decryption private key is used.

Hash Functions: No key is used in this algorithm. A fixed-length hash value is computed as per the plain text that makes it impossible for the contents of the plain text to be recovered. Hash functions are also used by many operating systems to encrypt passwords.

2. compare and contrast

Compare and contrast essays are multi-paragraph compositions that explain ways in which two (or occasionally more) subjects are similar and different. In these essays, compare means describing similarities between the subjects. The essay on farmlife versus city would provide at least one paragraph on how people's lives in the city are like the lives of the people that live on a farm. Basically, the comparison tells what they have in common.

When a writer contrasts two things, he or she explains ways in which they are different. After completing a unit of study on where people live, students should be able to provide several details about how life on a farm can be vastly different from life in a city.

Again, compare and contrast essays can cover almost any topic and may pop up in a variety of subject areas. In order to make decisions about what to include, writers need to keep one thing in mind: relevance. Relevance helps determine which characteristics are worth comparing and contrasting. Your thesis will help you determine the relevance, or irrelevance, of facts. That means writers need a strong thesis statement.

This is a sentence that lets the reader know the topic and the argument the writer is making. Something like: While city life and farm life have few similarities, city life provides the hustle and bustle of many people, distinct noises, and social opportunities that are different from that of farm life. If this is the writer's thesis statement, then the essay should focus on details that are relevant to the hustle and bustle of city life, noises, and social activities available in the city versus on a farm. The thesis statement will help keep the writing focused on just a few ideas that are based on the overall topic.