---
title: "What is cryptography"
subject: "Computer Networks and Security"
chapter: 8
key: "semester_7/computer_networks_and_security:what-is-cryptography"
source: https://www.bctengineer.com/q/semester_7/computer_networks_and_security/what-is-cryptography
site: BCT Engineering
---

# What is cryptography

Computer Networks and Security · Chapter 8: Network Security

- Asked in: 2071 Shrawan, 2 marks
- Video: [Lec-88: Cryptography in computer network in Hindi | Cryptography in Information Security](https://www.youtube.com/watch?v=trHox1bN5es) — Gate Smashers
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/computer_networks_and_security/what-is-cryptography
- Whole chapter: https://www.bctengineer.com/md/semester_7/computer_networks_and_security/chapter-8

## Question

What is cryptography?

## Short answer

Cryptography is the science of converting plaintext into ciphertext using algorithms and keys to provide confidentiality, integrity, authentication, and non-repudiation. Main kinds are symmetric-key, public-key, and hash functions. Encryption is the forward conversion; decryption is the reverse.

## Answer

**Cryptography** is the science and art of securing information by converting readable data (plaintext) into an unreadable form (ciphertext) using mathematical algorithms and keys, so only authorised parties can read or verify it. Its goals are confidentiality, integrity, authentication and non-repudiation.

Main kinds: symmetric-key cryptography (AES), public-key cryptography (RSA) and hash functions (SHA). The process of converting plaintext to ciphertext is **encryption**, and the reverse is **decryption**.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Cryptography is:
   A. Routing data
   B. Hiding the network
   C. Compressing files
   D. Securing information by converting plaintext to ciphertext using algorithms and keys
   Answer: D. It uses mathematical algorithms and keys so only authorised parties can read or verify data. (Key point: Definition)

2. Which is a goal of cryptography?
   A. Speed
   B. Addressing
   C. Confidentiality, integrity, authentication, non-repudiation
   D. Routing
   Answer: C. These are the four stated goals. (Key point: Goals)

3. Converting ciphertext back to plaintext is called:
   A. Signing
   B. Hashing
   C. Decryption
   D. Encryption
   Answer: C. Decryption is the reverse of encryption. (Key point: Terms)