By NATHAN REIFF
Updated Feb 1, 2020
TABLE OF CONTENTS
EXPAND
What is Blockchain?
How Blockchain Works
Is Blockchain Private?
Is Blockchain Secure?
Blockchain vs. Bitcoin
Public and Private Key Basics
Practical Applications
Pros and Cons of Blockchain
Disadvantages of Blockchain
What's Next for Blockchain?
If you have been following banking, investing, or cryptocurrency over the last ten years, you may be familiar with “blockchain,” the record-keeping technology behind the Bitcoin network. And there’s a good chance that it only makes so much sense. In trying to learn more about blockchain, you've probably encountered a definition like this: “blockchain is a distributed, decentralized, public ledger."
The good news is that blockchain is actually easier to understand than that definition sounds.
What is Blockchain?
If this technology is so complex, why call it “blockchain?” At its most basic level, blockchain is literally just a chain of blocks, but not in the traditional sense of those words. When we say the words “block” and “chain” in this context, we are actually talking about digital information (the “block”) stored in a public database (the “chain”).
“Blocks” on the blockchain are made up of digital pieces of information. Specifically, they have three parts:
Blocks store information about transactions like the date, time, and dollar amount of your most recent purchase from Amazon. (NOTE: This Amazon example is for illustrative purchases; Amazon retail does not work on a blockchain principle as of this writing)
Blocks store information about who is participating in transactions. A block for your splurge purchase from Amazon would record your name along with Amazon.com, Inc. (AMZN). Instead of using your actual name, your purchase is recorded without any identifying information using a unique “digital signature,” sort of like a username.
Blocks store information that distinguishes them from other blocks. Much like you and I have names to distinguish us from one another, each block stores a unique code called a “hash” that allows us to tell it apart from every other block. Hashes are cryptographic codes created by special algorithms. Let’s say you made your splurge purchase on Amazon, but while it’s in transit, you decide you just can’t resist and need a second one. Even though the details of your new transaction would look nearly identical to your earlier purchase, we can still tell the blocks apart because of their unique codes.
While the block in the example above is being used to store a single purchase from Amazon, the reality is a little different. A single block on the Bitcoin blockchain can actually store around 1 MB of data.1 Depending on the size of the transactions, that means a single block can house a few thousand transactions under one roof.
What Is the Blockchain?
How Blockchain Works
When a block stores new data it is added to the blockchain. Blockchain, as its name suggests, consists of multiple blocks strung together. In order for a block to be added to the blockchain, however, four things must happen:
A transaction must occur. Let’s continue with the example of your impulsive Amazon purchase. After hastily clicking through multiple checkout prompt, you go against your better judgment and make a purchase. As we discussed above, in many cases a block will group together potentially thousands of transactions, so your Amazon purchase will be packaged in the block along with other users' transaction information as well.
That transaction must be verified. After making that purchase, your transaction must be verified. With other public records of information, like the Securities Exchange Commission, Wikipedia, or your local library, there’s someone in charge of vetting new data entries. With blockchain, however, that job is left up to a network of computers. When you make your purchase from Amazon, that network of computers rushes to check that your transaction happened in the way you said it did. That is
good