Quantum Computing: Is it the end of blockchain?

Let’s start by understanding blockchain.

Disclaimer: I’ve tried to keep it simple, which could have abstracted the technical nuances. Moreover, please excuse my handwriting in all the descriptions. I felt they do a better job in describing concepts than a picture from the web.

In simple words, a blockchain is a ledger that records transactions of a certain type. It uses mathematical functions such as integer factorization, which is easy to solve in one direction but hard in the other direction for security.

The transactions in a blockchain are added to a database called a block, and the block is encrypted using a mathematical device called a hashing function. This hash is then included in the next block with the next set of transactions, which is then encrypted using the hashing function to produce a new hash. This new hash is added to the next block. And so on, creating a chain of blocks that are all nested inside the latest one — hence the name blockchain.

Here is an example of a hash generated by the MD5 algorithm in Python, which is a widely used hash function producing a 128-bit hash value.