Bitcoin Scripting

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Bitcoin, Not Blockchain
Have you ever heard a smart sounding friend say that they aren’t sure about bitcoin but they believe in blockchain technology? This is like saying you believe in airplanes but you’re not sure about the wings; and there’s a good chance that anyone who thinks that may not understand either. In reality, bitcoin and its blockchain are dependent on each other. However, if new to bitcoin, understanding how it works and parsing the landscape can be incredibly difficult. Frankly, it can be overwhelming; given the complexity and sheer volume of projects, who has the time to possibly evaluate everything? There is in fact a manageable path but you have to know where to start. While there are seemingly thousands of cryptocurrencies and blockchain initiatives, there is really only one that matters: bitcoin. Ignore everything else like it didn’t exist and first try to develop an understanding of why bitcoin exists and how it works; that is the best foundation to then be able to think about the entirety of everything else.

It is also the most practical entry point; before taking a flyer and risking hard-earned value, take the time to understand bitcoin and then use that knowledge to evaluate the field. There is no promise that you will come to the same conclusions, but more often than not, those who take the time to intuitively understand how and why bitcoin works more easily recognize the flaws inherent in the field. And even if not, starting with bitcoin remains your best hope of making an informed and independent assessment. Ultimately, bitcoin is not about making money and it’s not a get-rich-quick scheme; it is fundamentally about storing the value you have already created, and no one should risk that without a requisite knowledge base. Within the world of digital currencies, bitcoin has the longest track record to assess and the greatest amount of resources to educate, which is why bitcoin is the best tool to learn.

To start on this journey, first realize that bitcoin was created to specifically address a problem that exists with modern money. The founder of bitcoin set out to create a peer-to-peer digital cash system without the need for a trusted third-party, and a blockchain was one critical part of the solution. In practice, bitcoin (the currency) and its blockchain are interdependent. One does not exist without the other; bitcoin needs its blockchain to function and there would not be a functioning blockchain without a native currency (bitcoin) to properly incentivize resources to protect it. That native currency must be viable as a form of money because it is exclusively what pays for security, and it must have credible monetary properties in order to be viable.

Without the money, there is no security and without the security, the value of the currency and the integrity of the chain both break down. It is for this reason that a blockchain is only useful within the application of money, and money does not magically grow on trees. Yep, it is that simple. A blockchain is only good for one thing, removing the need for a trusted third-party which only works in the context of money. A blockchain cannot enforce anything that exists outside the network. While a blockchain would seem to be able to track ownership outside the network, it can only enforce ownership of the currency that is native to its network. Bitcoin tracks ownership and enforces ownership. If a blockchain cannot do both, any records it keeps will be inherently insecure and ultimately subject to change. In this sense, immutability is not an inherent trait of a blockchain but instead, an emergent property. And if a blockchain is not immutable, its currency will never be viable as a form of money because transfer and final settlement will never be reliably possible. Without reliable final settlement, a monetary system is not functional and will not attract liquidity.

Ultimately, monetary systems converge on one medium because their utility is liquidity rather than consumption or production. And liquidity consolidates around the most secure, long-term store of value; it would be irrational to store wealth in a less secure, less liquid monetary network if a more secure, more liquid network existed as an attainable option. The aggregate implication is that only one blockchain is viable and ultimately necessary. Every other cryptocurrency is competing for the identical use case as bitcoin, that of money; some realize it while others do not but value continues to consolidate around bitcoin because it is the most secure blockchain by orders of magnitude and all are competing for the same use case. Understanding these concepts is fundamental to bitcoin and it also provides a basic foundation to then consider and evaluate the noise beyond bitcoin. With basic knowledge of how bitcoin actually works, it becomes clear why there is no blockchain without bitcoin.

There is no blockchain
Often, bitcoin’s transaction ledger is thought of as a public blockchain that lives somewhere in the cloud like a digital public square where all transactions are aggregated. However, there is no central source of truth; there are no oracles and there is no central public blockchain to which everyone independently commits transactions. Instead, every participant within the network constructs and maintains its own independent version of the blockchain based on a common set of rules; no one trusts anyone and everyone validates everything. Everyone is able to come to the same version of the truth without having to trust any other party. This is core to how bitcoin solves the problem of removing third-party intermediaries from a digital cash system.


Every participant running a node within the bitcoin network independently verifies every transaction and every block; by doing so, each node aggregates its own independent version of the blockchain. Consensus is reached across the network because each node validates every transaction (and each block) based on a core set of rules (and the longest chain wins). If a node broadcasts a transaction or block that does not follow consensus rules, other nodes will reject it as invalid. It is through this function that bitcoin is able to dispose with the need for a central third-party; the network converges on the same consistent state of the chain without anyone trusting any other party. However, the currency plays an integral role in coordinating bitcoin’s consensus mechanism and ordering blocks which ultimately represents bitcoin’s full and valid transaction history (or its blockchain).

The basics of bitcoin: blocks and mining
Think of a block as a dataset that links the past to the present. Technically, individual blocks record changes to the overall state of bitcoin ownership within a given time interval. In aggregate, blocks record the entire history of bitcoin transactions as well as ownership of all bitcoin at any point in time. Only changes to the state are recorded in each passing block. How blocks are constructed, solved and validated is critical to the process of network consensus, and it also ensures that bitcoin maintains a fixed supply (21 million). Miners compete to construct and solve blocks that are then proposed to the rest of the network for acceptance. To simplify, think of the mining function as a continual process of validating history and clearing pending bitcoin transactions; with each block, miners add new transaction history to the blockchain and validate the entire history of the chain. It is through this process that miners secure the network; however, all network nodes then check the work performed by miners for validity, ensuring network consensus is enforced. More technically, miners construct blocks that represent data sets which include three critical elements (again simplifying):

Reference to prior block → validate entire history of chain
Bitcoin transactions → clear pending transactions (changes to the state of ownership)
Coinbase transaction + fees → compensation to miners for securing the network
To solve blocks, miners perform what is known as a proof of work function by expending energy resources. In order for blocks to be valid, all inputs must be valid and each block must satisfy the current network difficulty. To satisfy the network difficulty, a random value (referred to as a nonce) is added to each block and then the combined data set is run through bitcoin’s cryptographic hashing algorithm (SHA-256); the resulting output (or hash) must achieve the network’s difficulty in order to be valid. Think of this as a simple guess and check function, but probabilistically, trillions of random values must be guessed and checked in order to create a valid proof for each proposed block. The addition of a random nonce may seem extraneous. But, it is this function that forces miners to expend significant energy resources in order to solve a block, which ultimately makes the network more secure by making it extremely costly to attack.

Adding a random nonce to a proposed block, which is an otherwise static data set, causes each resulting output (or hash) to be unique; with each different nonce checked, the resulting output has an equally small chance of achieving the network difficulty (i.e. representing a valid proof). While it is often referred to as a highly complicated mathematical problem, in reality, it is difficult only because a valid proof requires guessing and checking trillions of possible solutions. There are no shortcuts; energy must be expended. A valid proof is easy to verify by other nodes but impossible to solve without expending massive amount of resources; as more mining resources are added to the network, the network difficulty increases, requiring more inputs to be checked and more energy resources to be expended to solve each block. Essentially, there is material cost to miners in solving blocks but all other nodes can then validate the work very easily at practically no cost.

In aggregate, the incentive structure allows the network to reach consensus. Miners must incur significant upfront cost to secure the network but are only paid if valid work is produced; and the rest of the network can immediately determine whether work is valid or not based on consensus rules without incurring cost. While there are a number of consensus rules, if any pending transaction in a block is invalid, the entire block is invalid. For a transaction to be valid, it must have originated from a previous, valid bitcoin block and it cannot be a duplicate of a previously spent transaction; separately, each block must build off the most up to date version of history in order to be valid and it must also include a valid coinbase transaction. A coinbase transaction rewards miners with newly issued bitcoin in return for securing the network but it is only valid if the work is valid.

Coinbase rewards are governed by a predetermined supply schedule and currently, 12.5 new bitcoin are issued in each valid block; in approximately eight months, the reward will be cut in half to 6.25 new bitcoin, and every 210,000 blocks (or approximately every four years), the reward will continue to be halved until it ultimately reaches zero. If miners include an invalid reward in a proposed block, the rest of the network will reject it as invalid which is the base mechanism that governs a capped total supply of 21 million bitcoin. However, software alone is insufficient to ensure either a fixed supply or an accurate transaction ledger; economic incentives hold everything together.