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‎bitcoin-script/LICENSE.md ‎LICENSE.md

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‎README.md

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# Programming Bitcoin Script Transaction (Crypto) Contracts Step-by-Step
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# Programming Bitcoin Script Transaction (Crypto) Contracts Step-by-Step
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Let's start with building your own bitcoin stack machine from zero / scratch and let's run your own bitcoin ops (operations)...
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_Let's start with building your own bitcoin stack machine from zero / scratch and let's run your own bitcoin ops (operations)..._
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Did you know? Every (yes, every) bitcoin transaction (payment) runs
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a contract script (one half coming from the "output" or "lock" transaction and the
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other half coming from the "input" or "unlock" transaction).
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The programming language is called simply (bitcoin) script.
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> Bitcoin uses a scripting system for transactions.
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> Forth-like, Script is simple, stack-based, and processed from left to right.
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> It is intentionally not Turing-complete, with no loops.
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>
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> (Source: [Script @ Bitcoin Wiki](https://en.bitcoin.it/wiki/Script))
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First impression. Adding 2+2 in Bitcoin Script starting from zero / scratch:
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``` ruby
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## A simple stack machine
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def op_add( stack )
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left = stack.pop
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right = stack.pop
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stack.push( left + right )
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end
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def op_2( stack )
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stack.push( 2 )
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end
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## Let's run!
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stack = []
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op_2( stack ) #=> stack = [2]
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op_2( stack ) #=> stack = [2,2]
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op_add( stack ) #=> stack = [4]
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```
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Yes, that's all the magic! You have built your own stack machine with
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two operations / ops, that is, `op_add` and `op_2`.
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Push and Pop
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The `op_2` operation pushes the number `2` onto the stack.
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The `op_add` operation pops the top two numbers from the stack
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and pushes the result onto the stack.
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In "real world" bitcoin the script has two parts / halves in two transactions
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that get combined.
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The "lock" or "output" or "ScriptSig" script
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that locks the "unspent transaction output (UTXO)"
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and the "unlock" or "input" or "ScriptPubKey" script that unlocks
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the bitcoins.
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Anyone Can Spend (Unlock) the Outputs (Bitcoins)
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The bitcoins are yours if the bitcoins haven't been spent yet -
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see blockchain and how it solves the double-spending problem :-) -
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AND if the script returns with true, that is, `1` is on top of the stack.
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``` ruby
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## A simple stack machine
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def op_true( stack )
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stack.push( 1 )
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end
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## Let's run!
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stack = []
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## scriptPubKey part
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## - Empty
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## scriptSig part
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op_true( stack ) #=> stack = [1]
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```
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Bingo! Yes, that's all the magic!
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The `op_true` operation pushes the number `1`, that is, `true` onto the stack.
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The "official" bitcoin script notation reads:
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```
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scriptPubKey: (empty)
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scriptSig: OP_TRUE
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```
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Now let's split the adding `2+2` script into a two part puzzle,
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that is, `?+2=4`
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or into `scriptSig` and `scriptPubKey`.
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If you know the answer you can "unlock" the bounty,
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that is, the bitcoin are yours!
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Here's the challenge:
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``` ruby
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## A simple stack machine
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def op_add( stack )
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left = stack.pop
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right = stack.pop
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stack.push( left + right )
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end
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def op_2( stack )
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stack.push( 2 )
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end
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def op_4( stack )
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stack.push( 4 )
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end
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def op_equal( stack )
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left = stack.pop
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right = stack.pop
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stack.push( left == right ? 1 : 0 )
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end
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## Let's run!
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stack = []
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## scriptPubKey part
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## - add your "unlock" stack operation / operations here
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## scriptSig part
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op_2( stack ) #=> stack = [?, 2]
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op_add( stack ) #=> stack = [4]
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op_4( stack ) #=> stack = [4,4]
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op_equal( stack ) #=> stack = [1]
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```
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The "official" bitcoin script notation reads:
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```
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scriptPubKey: ?
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scriptSig: OP_2 OP_ADD OP_4 OP_EQUAL
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```
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To be continued ...
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## Standard Scripts
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| Short Name | Long Name |
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|------------|------------|
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| p2pk | Pay-to-pubkey |
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| p2pkh | Pay-to-pubkey-hash |
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| p2sh | Pay-to-script-hash |
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| p2wpkh | Pay-to-witness-pubkey-hash |
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| p2wsh | Pay-to-witness-script-hash |
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## Resources
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Articles
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- [Bitcoin Script @ Bitcoin Wiki](https://en.bitcoin.it/wiki/Script)
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Books
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- [Programming Bitcoin from Scratch](https://github.com/jimmysong/programmingbitcoin) by Jimmy Song
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- [Chapter 6 - Script](https://github.com/jimmysong/programmingbitcoin/blob/master/ch06.asciidoc) - How Script Works • Example Operations • Parsing the Script Fields • Combining the Script Fields • Standard Scripts • p2pk • Problems with p2pk • Solving the Problems with p2pkh • Scripts Can Be Arbitrarily Constructed • Conclusion
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- [Chapter 8 - Pay-to-Script Hash](https://github.com/jimmysong/programmingbitcoin/blob/master/ch08.asciidoc) - Bare Multisig • Coding OP_CHECKMULTISIG • Problems with Bare Multisig • Pay-to-Script-Hash (p2sh) • Coding p2sh • Conclusion
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Talk Notes
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- [Contracts, Contracts, Contracts - Code Your Own (Crypto Blockchain) Contracts w/ Ruby (sruby), Universum & Co](https://github.com/geraldb/talks/blob/master/contracts.md)
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- Genesis - Bitcoin Script
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- Ivy - Higher-Level Bitcoin Script
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- History Corner - Bitcoin - The World's Worst Database for Everything? - Bitcoin Maximalism in Action
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- Turing Complete and the Halting Problem
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- Fees, Fees, Fees - $$$ - There's No Free Lunch
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## License
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![](https://publicdomainworks.github.io/buttons/zero88x31.png)
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The Programming Bitcoin Script Step-by-Step book / guide
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is dedicated to the public domain.
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Use it as you please with no restrictions whatsoever.

‎bitcoin-script/Manifest.txt

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CHANGELOG.md
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LICENSE.md
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Manifest.txt
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README.md
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Rakefile

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