7 ms·

A blockchain in 200 lines of code

326 points by bpierre 10y ago

jamiehoward 10y ago
I'm not familiar with blockchains. Super interesting idea.
logicallee 10y ago
I wonder if anyone thought of making a distributed operating system where 1-2 million people could all run a NINTENDO console or something else extremely primitive - but in way that they KNOW no one is pulling any shenanigans. Can you imagine how cool it would be if a million or, say, a hundred million people joined forces to do what a $60 mobile phone can do? This is absolutely the future. No doubt about it. No one can ever conceivably come up with a paradigm as cool as this level of redundancy. And on top of all of this, it even works. (Not as designed, because 51% of miners may be controlled by one entity, but in practice it totally works.)
- frik 10y ago
  sounds like Ethereum: https://en.wikipedia.org/wiki/Ethereum https://en.wikipedia.org/wiki/Ethereum "Ethereum is an open-source, public, blockchain-based distributed computing platform featuring smart contract (scripting) functionality. It provides a decentralized virtual machine, the Ethereum Virtual Machine (EVM). This virtual machine can execute Turing-complete scripts using an international network of public nodes and a token called ether. Gas, an internal transaction pricing mechanism, is used to prevent spam on the network and allocate resources proportionally to the incentive offered by the request" Unrelated, I remember an experiment on Twitch, where hundreds of viewers controlled/played Pokémon Yellow (Gameboy emulator) live on Twitch via chat commands like "left", "right". It more or less worked out fine, but was rather slow progress.
  - JoshTriplett 10y ago
    > Unrelated, I remember an experiment on Twitch, where hundreds of viewers controlled/played Pokémon Yellow (Gameboy emulator) live on Twitch via chat commands like "left", "right". It more or less worked out fine, but was rather slow progress. https://en.wikipedia.org/wiki/Twitch_Plays_Pok%C3%A9mon https://en.wikipedia.org/wiki/Twitch_Plays_Pok%C3%A9mon
  - wayn3 10y ago
    except twitch plays pokemon was meant for entertainment. the purposeless waste of resources on bitcoin is a cult, believed to enlighten the world.
- deleted 10y ago
  [deleted]
- gcr 10y ago
  BOINC pioneered this sort of shared computation to do massively data parallel experiments for astrophysics research in the early 00s. I think they still do. These days, I think the hardware investment is much lower than the software+infrastructure+social investment of running your experiment on BOINC.
  - tech_man7 10y ago
    The Golem team (https://golem.network/ https://golem.network/) got their inspiration from BOINC. But now more people will have incentive to share their compute power because they will be paid.
  - Lev1a 10y ago
    IIRC the focus of these kinds of infrastructures has shifted towards protein folding [1] which could IMO prove more useful than astrophysics. [1] https://en.wikipedia.org/wiki/Protein_folding https://en.wikipedia.org/wiki/Protein_folding
- tech_man7 10y ago
  That is what Golem is building (https://golem.network/ https://golem.network/). Decentralized compute power that is a global P2P network of PCs. The platform will allow software developers to put their software on top as long as its approved (e.g. to make sure it's not malicious).
- logicallee 10y ago
  For anyone reading this later: the above was sarcastic but I left off the /s. I don't think blockchains are that great of a fundamental primitive. Though, independent of application, they were extemely novel.
  - tech_man7 10y ago
    you don't need a blockchain for computations; only for transferring value from buyer to seller.
hdhzy 10y ago
One caveat: Bitcoin doesn't choose longest chain by the number of blocks but rather the difficulty, see https://en.bitcoin.it/wiki/Difficulty https://en.bitcoin.it/wiki/Difficulty
- chjj 10y ago
  More specifically, it chooses by cumulative work. Bitcoin needs that behavior because of retargetting (a lesser height chain may have required more proof of work to build than a higher height one). If your custom blockchain has a static target, choosing the best chain by height is perfectly fine. Though, I'm not sure how useful a blockchain without retargetting or POW would be.
tromp 10y ago
Real blockchains do have a blockheader.prevHash field to indicate that the previous block is the one satisfying HASH(prevheader) == blockheader.prevHash This one actually adds a blockheader.hash field and instead compares prevheader.hash == blockheader.prevHash Naive indeed:-)
- runeks 10y ago
  Good video+interactive explanation: https://anders.com/blockchain/ https://anders.com/blockchain/
bascule 10y ago
Though blockchain is an ill-defined term, this seems to be missing the most important part of one: consensus. Bitcoin achieves this in two ways: - Proof-of-Work, which effectively functions as a leader election algorithm - Consensus programs, which mediate any changes to the blockchain. Each Bitcoin transaction has an associated script that determines how it can be spent. A conforming block satisfies all of the scripts for all of the transactions being spent. This particular post illustrates something which I would say is little more than a Merkle tree[1], except it isn't even that. But perhaps it's illustrative for some people. [1]: https://en.wikipedia.org/wiki/Merkle_tree https://en.wikipedia.org/wiki/Merkle_tree
- kordless 10y ago
  I suppose we could look at consensus as means by which multiple blockchains are collapsed into a single chain which contains the "truth" for multiple entities or aggregates. Once a collapse or consensus occurs, the chain, regardless of who holds it, would contain the truth.
  - throwaway91111 10y ago
    Without consensus, what distinguishes a block chain from a Merkle tree?
    - saurik 10y ago
      The Merkle tree is only used within a Bitcoin block to store transactions in an efficient manner; it isn't part of the block chain. A block chain without consensus isn't even a tree: it is just a singly-linked list with cryptographic guarantees that given a linked list node, all previous entries can be "verified". However, as other people have pointed out, this implementation is so incorrect that it fails to even do that: it contains only the hash of the previous data, not the hash of the previous node, so this actually only manages to verify the previous one entry of the chain :/. This is essentially just a linked list :(.
      - 10y ago
mamon 10y ago
Is this just me or is this blockchain algorithm really similar to stringing together commits in Git? Can Git be considered "blockchain" application?
- lisper 10y ago
  Yep. Git and blockchains both use Merkle trees to keep a consistent history. https://news.ycombinator.com/item?id=9436847 https://news.ycombinator.com/item?id=9436847
- deleted 10y ago
  [deleted]
- throwawayish 10y ago
  The hash tree (Merkle Tree) is only part of it. The proof-of-work and consensus / voting protocols are the other (main) part.
  - OJFord 10y ago
    Which this doesn't have.
- oconnor663 10y ago
  There are lots of different applications where one part of a data structure refers to another part by its hash. BitTorrent is one. HTTPS certificates also do some of this I think.
spraak 10y ago
I don't understand why someone would use an ES6 feature like arrow funcs, but still use `var`
- inimino 10y ago
  Because nothing is wrong with `var` and arrow functions are more concise?
  - TheDong 10y ago
    > nothing is wrong with var Other than having utterly illogical scoping. Which is the entire reason 'let' was introduced and should always be preferred.
    - inimino 10y ago
      Please. There's nothing illogical about it. It scopes to the function body. Maybe you meant to write "unfamiliar".
      - nv-vn 10y ago
        It's entirely unintuitive, inconsistent with the syntax, and is generally senseless. "var" lacks an easy to explain meaning because in many cases it doesn't even introduce a variable.
        inimino 10y ago
        It ensures that a variable is declared in the current scope. That's the easy to explain meaning. It's inconsistent with other languages which introduce a new scope whenever there are curly braces, but there's nothing inconsistent about the syntax. That's just a matter of taking expectations from other languages and expecting them to work unchanged in JavaScript.
kang 10y ago
There is not a single use-case that this code can achieve, which you couldn't before the invention of bitcoin. Blockchains are just linked lists; without proof-of-work its useless.
davidgerard 10y ago
This is a good example of how in 2017, Merkle trees will be renamed "blockchain" in marketing parlance.
AKifer 10y ago
That's exactly what we need, a Hello world of the blockchain technology. Everybody talks about these data structures while it's very rare to find concrete example of even a simple implementation. It's not helping to be said go look at bitcoin source code.
- carlosgj94 10y ago
  This may help you also: https://anders.com/blockchain/ https://anders.com/blockchain/. In fact is quite better, since it adds more info. Also the code of it is on github ;)

326 points by bpierre 10y ago

I'm not familiar with blockchains. Super interesting idea.

I wonder if anyone thought of making a distributed operating system where 1-2 million people could all run a NINTENDO console or something else extremely primitive - but in way that they KNOW no one is pulling any shenanigans. Can you imagine how cool it would be if a million or, say, a hundred million people joined forces to do what a $60 mobile phone can do? This is absolutely the future. No doubt about it. No one can ever conceivably come up with a paradigm as cool as this level of redundancy. And on top of all of this, it even works. (Not as designed, because 51% of miners may be controlled by one entity, but in practice it totally works.)

frik 10y ago
sounds like Ethereum: https://en.wikipedia.org/wiki/Ethereum https://en.wikipedia.org/wiki/Ethereum "Ethereum is an open-source, public, blockchain-based distributed computing platform featuring smart contract (scripting) functionality. It provides a decentralized virtual machine, the Ethereum Virtual Machine (EVM). This virtual machine can execute Turing-complete scripts using an international network of public nodes and a token called ether. Gas, an internal transaction pricing mechanism, is used to prevent spam on the network and allocate resources proportionally to the incentive offered by the request" Unrelated, I remember an experiment on Twitch, where hundreds of viewers controlled/played Pokémon Yellow (Gameboy emulator) live on Twitch via chat commands like "left", "right". It more or less worked out fine, but was rather slow progress.
- JoshTriplett 10y ago
  > Unrelated, I remember an experiment on Twitch, where hundreds of viewers controlled/played Pokémon Yellow (Gameboy emulator) live on Twitch via chat commands like "left", "right". It more or less worked out fine, but was rather slow progress. https://en.wikipedia.org/wiki/Twitch_Plays_Pok%C3%A9mon https://en.wikipedia.org/wiki/Twitch_Plays_Pok%C3%A9mon
- wayn3 10y ago
  except twitch plays pokemon was meant for entertainment. the purposeless waste of resources on bitcoin is a cult, believed to enlighten the world.
deleted 10y ago
[deleted]
gcr 10y ago
BOINC pioneered this sort of shared computation to do massively data parallel experiments for astrophysics research in the early 00s. I think they still do. These days, I think the hardware investment is much lower than the software+infrastructure+social investment of running your experiment on BOINC.
- tech_man7 10y ago
  The Golem team (https://golem.network/ https://golem.network/) got their inspiration from BOINC. But now more people will have incentive to share their compute power because they will be paid.
- Lev1a 10y ago
  IIRC the focus of these kinds of infrastructures has shifted towards protein folding [1] which could IMO prove more useful than astrophysics. [1] https://en.wikipedia.org/wiki/Protein_folding https://en.wikipedia.org/wiki/Protein_folding
tech_man7 10y ago
That is what Golem is building (https://golem.network/ https://golem.network/). Decentralized compute power that is a global P2P network of PCs. The platform will allow software developers to put their software on top as long as its approved (e.g. to make sure it's not malicious).
logicallee 10y ago
For anyone reading this later: the above was sarcastic but I left off the /s. I don't think blockchains are that great of a fundamental primitive. Though, independent of application, they were extemely novel.
- tech_man7 10y ago
  you don't need a blockchain for computations; only for transferring value from buyer to seller.

hdhzy 10y ago

One caveat: Bitcoin doesn't choose longest chain by the number of blocks but rather the difficulty, see https://en.bitcoin.it/wiki/Difficulty https://en.bitcoin.it/wiki/Difficulty

chjj 10y ago
More specifically, it chooses by cumulative work. Bitcoin needs that behavior because of retargetting (a lesser height chain may have required more proof of work to build than a higher height one). If your custom blockchain has a static target, choosing the best chain by height is perfectly fine. Though, I'm not sure how useful a blockchain without retargetting or POW would be.

tromp 10y ago

Real blockchains do have a blockheader.prevHash field to indicate that the previous block is the one satisfying HASH(prevheader) == blockheader.prevHash This one actually adds a blockheader.hash field and instead compares prevheader.hash == blockheader.prevHash Naive indeed:-)

runeks 10y ago
Good video+interactive explanation: https://anders.com/blockchain/ https://anders.com/blockchain/

bascule 10y ago

Though blockchain is an ill-defined term, this seems to be missing the most important part of one: consensus. Bitcoin achieves this in two ways: - Proof-of-Work, which effectively functions as a leader election algorithm - Consensus programs, which mediate any changes to the blockchain. Each Bitcoin transaction has an associated script that determines how it can be spent. A conforming block satisfies all of the scripts for all of the transactions being spent. This particular post illustrates something which I would say is little more than a Merkle tree[1], except it isn't even that. But perhaps it's illustrative for some people. [1]: https://en.wikipedia.org/wiki/Merkle_tree https://en.wikipedia.org/wiki/Merkle_tree

kordless 10y ago
I suppose we could look at consensus as means by which multiple blockchains are collapsed into a single chain which contains the "truth" for multiple entities or aggregates. Once a collapse or consensus occurs, the chain, regardless of who holds it, would contain the truth.
- throwaway91111 10y ago
  Without consensus, what distinguishes a block chain from a Merkle tree?
  - saurik 10y ago
    The Merkle tree is only used within a Bitcoin block to store transactions in an efficient manner; it isn't part of the block chain. A block chain without consensus isn't even a tree: it is just a singly-linked list with cryptographic guarantees that given a linked list node, all previous entries can be "verified". However, as other people have pointed out, this implementation is so incorrect that it fails to even do that: it contains only the hash of the previous data, not the hash of the previous node, so this actually only manages to verify the previous one entry of the chain :/. This is essentially just a linked list :(.
    - 10y ago

mamon 10y ago

Is this just me or is this blockchain algorithm really similar to stringing together commits in Git? Can Git be considered "blockchain" application?

lisper 10y ago
Yep. Git and blockchains both use Merkle trees to keep a consistent history. https://news.ycombinator.com/item?id=9436847 https://news.ycombinator.com/item?id=9436847
deleted 10y ago
[deleted]
throwawayish 10y ago
The hash tree (Merkle Tree) is only part of it. The proof-of-work and consensus / voting protocols are the other (main) part.
- OJFord 10y ago
  Which this doesn't have.
oconnor663 10y ago
There are lots of different applications where one part of a data structure refers to another part by its hash. BitTorrent is one. HTTPS certificates also do some of this I think.

spraak 10y ago

I don't understand why someone would use an ES6 feature like arrow funcs, but still use `var`

inimino 10y ago
Because nothing is wrong with `var` and arrow functions are more concise?
- TheDong 10y ago
  > nothing is wrong with var Other than having utterly illogical scoping. Which is the entire reason 'let' was introduced and should always be preferred.
  - inimino 10y ago
    Please. There's nothing illogical about it. It scopes to the function body. Maybe you meant to write "unfamiliar".
    - nv-vn 10y ago
      It's entirely unintuitive, inconsistent with the syntax, and is generally senseless. "var" lacks an easy to explain meaning because in many cases it doesn't even introduce a variable.
      - inimino 10y ago
        It ensures that a variable is declared in the current scope. That's the easy to explain meaning. It's inconsistent with other languages which introduce a new scope whenever there are curly braces, but there's nothing inconsistent about the syntax. That's just a matter of taking expectations from other languages and expecting them to work unchanged in JavaScript.

kang 10y ago

There is not a single use-case that this code can achieve, which you couldn't before the invention of bitcoin. Blockchains are just linked lists; without proof-of-work its useless.

davidgerard 10y ago

This is a good example of how in 2017, Merkle trees will be renamed "blockchain" in marketing parlance.

AKifer 10y ago

That's exactly what we need, a Hello world of the blockchain technology. Everybody talks about these data structures while it's very rare to find concrete example of even a simple implementation. It's not helping to be said go look at bitcoin source code.

carlosgj94 10y ago
This may help you also: https://anders.com/blockchain/ https://anders.com/blockchain/. In fact is quite better, since it adds more info. Also the code of it is on github ;)