## Part One

Kleintje of a big overeenkomst. You’d have to be a total square not to have heard about them. Mij? I’ve got eight.

Often over-complicated, over-mysticised, over-singularised (I don’t even know what the right word for it is, but people say The Blockchain a loterijlot). What are they? Join mij for a rough tour from the ground up and I’ll attempt to make sure you leave here knowing the response to one question:

What are people talking about when they talk about blockchains?

There’s a lotsbestemming to voorkant, so it’s actually going to come ter two parts. This, the very first, will look at the gegevens structures known spil blockchains and their properties, along with any other onverdraagzaam and chunks you need to make sense of them.

The 2nd part will apply what you’ve learnt to the practical and widespread applications of blockchains to power distributed ledgers, cryptocurrencies such spil Bitcoin and Litecoin and smart-contract based chains like Ethereum.

## Hashes

Before wij leap into defining blockchains themselves, wij need to voorkant one concept which is so core to their working it makes absolutely no sense not to bring everyone up to speed.

That concept is what’s known spil a hash . Related is hashing , the activity by which wij get our forearms on a hash, and a hash function , the specific algorithm you run.

I’ll not go into how different hashing algorithms work, since there are many and that’s not the significant thing to know about them at this point. What’s significant is how they behave.

A hashing algorithm is a transformation that you can apply to any chunk of gegevens, long or brief, and get an output which will always be the same length. What that length actually is depends on the specific algorithm, but any given algorithm will always produce hashes of the same length.

For a concrete example, let’s look at SHA256, a popular and common hashing algorithm. This the hash of the string unwttng :

A petite note: whilst the ",256", te SHA256 refers to the fact that the output is exactly 256 vinnig long, it’s fairly customary to represent hashes ter hexadecimal notation (that is, using 0-9 and a-f) – that’s what wij’ll use te this article.

Spil long spil wij always use SHA256 to perform the hash, ",unwttng", will always produce this precies output, and any string will produce a hash of exactly 64 characters te length. Take a look at the hash of a totally different string:

The above is true of any hashing algorithm. However, there are a few more properties that are also commonly expected of a good hash function.

Uniformity of the hash function says that wij want any given hash output to be te some sense identically likely (or close to it). That is, if wij compute millions and millions of hashes using the function, there shouldn’t be any real pattern to where the outputs fall te the possible space of outputs. There shouldn’t be fountains of them that commence with an ",A",, or fountains that end with ten ",X",s, or anything like that.

Uniformity is a very significant feature because it minimises the risk that hashing any two inputs will produce the same output to vanishingly petite probabilities. Most practical usage of hashing across all kinds of software is done under the assumption that accidental ",collisions", of this kleuter are effectively unlikely.

Non-invertibility is another feature that’s often desirable, depending on the intended usage of the algorithm. This says that it should be unlikely, or at least prohibitively difficult, to work out the input that led to any given hash. Ideally, it should be effortless to convert gegevens into a hash, and practically unlikely to go the other way.

Eventually, discontinuity tells us to expect that similar inputs will produce drastically different hashes. There are algorithms with very specific (usually search-related) applications that aim for the opposite of this, but most hash functions that you come across will be spil non-continuous spil possible. The difference inbetween the hash of ‘abcdefg’ and ‘abcdefh’ should be almost total, rather than them differing by only one or a few characters.

Attempt it out for yourself! The below will let you explore SHA-256 – waterput anything you like ter the input and witness the hash switch. Attempt and observe the properties I’ve listed above if you can.