[Day 3] 1. Introduction to Cryptography

Introduction to PKI

Why is PKI included in the syllabus? PKI (Public Key Cryptography Infrastructure) is crucial for two main reasons:

1. Secure Communication and Storage: How can computers securely communicate and store data?
2. Trust Building: Computers operate based on trust. So, how can trust be established between different computers?

PKI is called an "infrastructure" because it involves a collection of entities, not just a single one.

---

Cryptography Overview

Cryptography is essentially about hiding data.

Definition:
It refers to methods of storing and transmitting data in a form that only authorized users can read and process. Various algorithms are used for this purpose.

There are two types of data:

1. Data in Transit
2. Data at Rest

Cryptography is aimed at protecting both types of data.

Goals of Cryptography:

• Make attacks more difficult for the attacker.
• Make it practically impossible for an attacker to break the code.

Note:
While cryptography can significantly enhance security, no system is 100% secure. Every lock or computer system can potentially be broken.

---

Key Terms in Cryptography

• Plaintext: The original, readable data before encryption.

• Access Control: Techniques used to restrict access to certain resources (e.g., username and password).

• Encryption: The process of converting plaintext into ciphertext (a non-human-readable format).

• Decryption: The reverse of encryption; converting ciphertext back into plaintext.

• Cryptanalysis: The study of breaking encryption methods.

• Cryptology: The study of both cryptanalysis and cryptography.

• Encryption Algorithm: A set of complex mathematical rules used to encrypt data.

• Encipher: Another term for encryption; converting plaintext into ciphertext.

• Decipher: Another term for decryption; converting ciphertext back into plaintext.

• Receipt: An acknowledgment that a process has been completed.

Note:

• Hashing is a one-way function (you can’t reverse it).
• Encryption is a two-way function (you can encrypt and decrypt).

---

Interesting Point:

Courses at CDAC are designed to help you build secure systems, while in PG DITISS, you learn to break systems to understand how they can be attacked or compromised.

---