Blockchain

What Is Proof-of-Work (PoW)?

What Is Proof-of-Work (PoW)?

Consensus protocols are used to verify and validate transactions. There are different kinds of consensus protocols and their different ways for the verification and validation of transactions.

In Proof-of-work (PoW), a miner or a group of miners will solve a mathematical equation to add a new block of transactions. The first miner to solve the mathematical equation will add the block in the existing blockchain. He will be rewarded with validated tokens.

An American computer scientist named Cynthia Dwork and an Israeli computer scientist named Moni Naor invented the concept of PoW. A computer security researcher, entrepreneur, and writer named Markus Jakobsson and another researcher named Ari Juels both coined and formalized PoW in a paper in 1999 for the first time.

PoW is based upon SHA-256. The National Security Agency is a US-based intelligence agency who has designed Secure Hash Algorithms (SHA or SHA-0, SHA1, and SHA2). Secure Hash Algorithms are defined as a family of cryptographic hash functions. While the National Institute of Standards and Technology (NIST) is a physical sciences laboratory and a non-regulatory agency who has published SHA or SHA-0 in 1993, SHA-1 was published in 1995, and SHA-2 (SHA-256) in 2001. SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224, and SHA-512/256 belong to the SHA-2 family. SHA or SHA-0 is called as a predecessor of SHA1 while SHA-1 is called as a predecessor of SHA-2. SHA-3 is designed by Belgian cryptographers named Joan Daemen and Gilles Van Assche and other cryptographers named Guido Bertoni and Michaël Peeters. It was published in 2015 by NIST. SHA-2 is called as a predecessor of SHA-3. The main purpose of SHA-256 is to generate a fixed size 256-bit (32-byte) hash.

Cryptographic Hash Function

A hash function which is used in cryptography called as a cryptographic hash function. A cryptography hash function is defined as a mathematical equation or algorithm which converts data of arbitrary size into a bit string of a fixed size. Checksums, Hash, Hash Value, and Message Digest are the other names of the bit string. Cryptographic hash functions are widely known as a basic tool for modern cryptography. They have applications in a mathematical scheme called digital signature and a tag or a short piece of information called message authentication code (MAC).

The properties of an ideal cryptographic hash function are:

  1. The same message will be the same hash
  2. Hashes for different types of messages will be computed instantly 
  3. A hash will not be computed for two different messages 
  4. If a message is slightly changed, then a new hash will be computed. The new hash will be different from the previous one. 

51% Attack

51% attack is defined as a hypothetical situation. An individual attacker or a group of attackers can gain 51% of the total computational power of a blockchain network to create a fraudulent block. They will be able to control the network completely. New transactions can be halted from confirmation. Payments can be stopped between various blockchain users. A completed transaction can be reversed. Double-spending of crypto coins can be allowed.

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