Cryptography in Blockchain

Apr 29, 2022 By Puneet verma

Contents

1. Introduction
2. Properties
3. Common terms in cryptographic
4. Type of cryptography
- 4.1 Symmetric
- 4.2 Asymmetric
5. How do we achieve confidentiality?
6. How do we achieve authentication?
7. Achieve both confidentiality and authentication
8 .Hash Function vs cryptographic Hash Function
9. Hashing vs Encrption
10. Cryptography in Blockchain

Cryptography is the method of securing data from unauthorised access. When we say Cryptography, we are looking for the following.

Confidentiality
Integrity
Non-repudiation
Authentication

Before going to blockchain in cryptography, let's first understand cryptography.

Confidentiality

The information cannot be understood by anyone for whom it was unintended. Except for the sender and receiver, no one can read the message.

Integrity

Integrity is used to ensure that nobody in between the sender and receiver can change some parts of the message.

Non-repudiation

The sender can't deny that he has not sent that message at a later stage.

Authentication

To verify the identity of who created the message.

Commons terms in cryptographic

Encryption: It is a process of converting plaintext to ciphertext.

Decryption: It is a process of converting ciphertext to plaintext.

Cipher: It is the unreadable output of an encryption algorithm.

Key: A key is a piece of information. Usually, a string of numbers or letters, which, when processed through a cryptographic algorithm, can encode or decode cryptographic data.

Type of cryptography

Symmetric key cryptography

It uses the same key to encrypt and decrypt information.

symmetric key cryptography

Asymmetric key cryptography

In asymmetric cryptography, we have a pair of public and private keys. The public key is used to encrypt the data, while the private key decrypts the data.

The public key is known to everybody, while the private key is secret.

Whoever wants to send a message to any receiver uses the receiver's public key to encrypt the data, and the receiver uses its private key to decrypt the data.

asymmetric key cryptography

How do we achieve confidentiality?

Anyone can send a message to B by using B's public, But only B can read that message using its private key.

confidentiality

How do we achieve authentication?

Suppose the sender uses his private key and encrypts the message if the receiver can decrypt the message with A's public key. That means the information came from A. This is called Digital Signature.

But the problem is that everybody has A's public and can decrypt the message. This breaks confidentiality.

digital signature

How do we achieve both confidentiality and authentication?

This is a fascinating setup, where A will use his private key to encrypt the data, and then A will use B's Public key to encrypt it again.

On the receiver end, B will first use his private key to decrypt the. This gives confidentiality. Then B will use A's public key to once again decrypt the data, and this is the way we achieve authentication.

confidentiality & authentication

What is the difference between a Hash Function and a Cryptographic Hash Function?

Every cryptographic hash function is a hash function. But not every hash function is a cryptographic hash.
Concept-wise, they are the same,
We consider a hash function as a cryptographic hash function when it hard to find collisions or pre-images

Case Study MD5 is broken.

Earlier, MD5 was considered a cryptographic hash function, but in 2008, we found that we could easily find collisions. We should not use MD5, as it is less secure.

Wiki

StackOverflow

Hashing vs Encrption

Encryption is a two-way function that includes encryption and decryption, while hashing is a one-way function that changes a plain text to an irreversible unique digest.
Hashing is used to validate the integrity. While encryption encodes data for the primary purpose of maintaining data confidentiality and security. It requires a private key to decrypt.
They are similar in the sense that they both transform data into a different format.