are extremely useful functions that appear in many information security

applications called the hash functions. We discuss the use of hash functions

in blockchain, hash function security for blockchain, and types of hash

functions. We explain that a credential of establishing whether a public key

belongs to the intended owner is done by the digital certificate and know

how to obtain a digital certificate.

After reading this chapter, you will be able to understand the basics of

algorithms and how they are used in cryptography, identify the differences

between asymmetric and symmetric algorithms, understand concepts of

cryptography, and how they relate to network security.

Introducing cryptography

The method of securing messages/ information and communication through

wires by using codes so that only those for whom the message/ information

is intended can read and process it. The words “hidden” or “vault” stand for

“crypt” and the word “writing” stands for “graphy”.

The mathematical concepts, protocols, rule-based calculations called

algorithms are used to transform messages that are hard to decipher and

secure messages/ information and communication by cryptography in

computer science. For digital signing, protecting data privacy, Internet Web

browsing, verification of cryptographic key generation, and confidential

communications such as credit/ debit card transactions and e-mail, these

algorithms are used, which are deterministic in nature.

A cipher is a cryptographic algorithm, a mathematical function used by the

encryption and decryption process.

A key which may be a word, a number, or a phrase, is used to encrypt the

plaintext, and it works in combination with a cryptographic algorithm.

The same plaintext encrypts to different ciphertext with different keys.

The following figure shows cryptography at work: