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<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
<title>Block Chain</title>
<link rel="stylesheet" href="css/reveal.css">
<link rel="stylesheet" href="css/theme/simple.css">
<!-- Theme used for syntax highlighting of code -->
<link rel="stylesheet" href="lib/css/xcode.css">
<!-- Theme override for teachbitcoin -->
<link rel="stylesheet" href="css/teachbitcoin.css">
<!-- Google Font Roboto -->
<link href="https://fonts.googleapis.com/css?family=Open+Sans:300,400,400i,600" rel="stylesheet">
<link href="https://fonts.googleapis.com/css?family=Roboto+Mono" rel="stylesheet">
</head>
<body>
<div class="reveal">
<div class="slides">
<!-- *********** Begin: headers *********** -->
<section class = "box">
<div class = "title">
Bitcoin Block <span class = "title weight">Headers</span>
</div>
<!-- Derivation Graphic -->
<img src="images/blockchain/headers.svg" class = "image" style = "z-index: -1;">
<!-- 2 column container -->
<!-- 45% div for formula and curve--><!-- 45% text & bulletpoint -->
<div class = "multi_text_box_container" style = "padding: 0px 0 0 0; width: 1350px;">
<!-- 45% div for formula and curve-->
<div class = "" style = "width: 60%; font-size: 22px;">
<div style ="text-align: center;">
</div>
</div>
<!-- 45% text & bulletpoint -->
<div class = "text_box"
style = "width: 47%; font-size: 20px; margin: 30px 0 0 0">
<ul style = "margin: 0; padding: 0px; list-style-type: none;">
<li style = "font-weight: bold;">Version:</li>
<ul>
<li>Version 2: Height in Coinbase Input Script (BIP34)</li>
<li>Version 3: Strict DER (BIP66)</li>
<li>Version 4: CLTV support (BIP65)</li>
</ul>
<li style = "font-weight: bold;">Merkle Root:</li>
<ul>
<li>Commits all transactions and their order.</li>
</ul>
<li style = "font-weight: bold;">Timestamp:</li>
<ul>
<li>POSIX time:</li>
<li>Must be higher than median of previous 11 blocks</li>
<li>Cannot more than 2hrs higher than local peer clock</li>
</ul>
<li style = "font-weight: bold;">Difficulty Bits:</li>
<ul>
<li>Defines target for POW</li>
<li>Block hash must be below target</li>
</ul>
<li style = "font-weight: bold;">Nonce:</li>
<ul>
<li>Iterated for POW</li>
</ul>
<li style = "font-weight: bold;">Block Hash:</li>
<ul>
<li>Double sha256 of serialised 80B header</li>
</ul>
</ul>
</div>
</div><!-- End of 2 column container -->
</section>
<!-- *********** END: headers *********** -->
<!-- *********** Begin: Genesis *********** -->
<section class = "box">
<div class = "title">
<span class = "title weight">Genesis</span> Block
</div>
<!-- Derivation Graphic -->
<img src="images/blockchain/genesis0.svg" class = "image" style = "z-index: -1;">
<img src="images/blockchain/genesis1.svg" class = "fragment image" style = "z-index: -1;">
<!-- 2 column container -->
<!-- 45% div for formula and curve--><!-- 45% text & bulletpoint -->
<div class = "multi_text_box_container" style = "padding: 0px 0 0 0; width: 1350px;">
<!-- 45% div for formula and curve-->
<div class = "" style = "width: 60%; font-size: 22px;">
<div style ="text-align: center;">
</div>
</div>
<!-- 45% text & bulletpoint -->
<div class = "text_box"
style = "width: 47%; font-size: 20px; margin: 20px 0 0 0">
<ul style = "margin: 0; padding: 0px; list-style-type: none;">
<li style = "font-weight: bold;">Block header:</li>
<ul>
<li>No previous block hash.</li>
<li>Timestamp:</li>
<ul>
<li>6:15:05 PM, Jan 3rd, 2009</li>
</ul>
<li>Difficulty bits:</li>
<ul>
<li>Lowest accepted difficulty bits.</li>
</ul>
</ul>
<hr style = "height: 5px; visibility: hidden;">
<li style = "font-weight: bold;">Transactions:</li>
<ul>
<li>First TX is always coinbase.</li>
<li>Coinbase input script:</li>
<ul>
<li>Version 1: Arbitrary data</li>
<li>Genesis block:</li>
<ul>
<li>Difficulty bits.</li>
<li>Times heading proves block originated afterwards.</li>
</ul>
</ul>
<li>Difficulty Bits:</li>
<ul>
<li>Lowest accepted difficulty bits.</li>
</ul>
</ul>
<hr style = "height: 5px; visibility: hidden;">
</ul>
</div>
</div><!-- End of 2 column container -->
</section>
<!-- *********** END: Genesis *********** -->
<!-- *********** Begin: Difficulty *********** -->
<section class = "box">
<div class = "title">
<span class = "title weight">Difficulty & Target</span>
</div>
<!-- Derivation Graphic -->
<img src="images/blockchain/difficulty0.svg" class = "image" style = "z-index: -1;">
<img src="images/blockchain/difficulty1.svg" class = "fragment image" style = "z-index: -1;">
<!-- 2 column container -->
<!-- 45% div for formula and curve--><!-- 45% text & bulletpoint -->
<div class = "multi_text_box_container" style = "padding: 0px 0 0 0; width: 1270px;">
<!-- 45% div for formula and curve-->
<div class = "" style = "width: 60%; font-size: 22px;">
<div style ="text-align: center;">
</div>
</div>
<!-- 45% text & bulletpoint -->
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style = "width: 47%; font-size: 22px; margin: 40px 0 0 0">
<ul style = "margin: 0; padding: 0px; list-style-type: none;">
<li style = "font-weight: bold;">Valid Header Hash must be <= target</li>
<hr style = "height: 5px; visibility: hidden;">
<li style = "font-weight: bold;">Miner can iterate following data in block:</li>
<ul>
<li>Nonce.</li>
<li>Unused version bits.</li>
<li>Timestamp.</li>
<li>Coinbase (Merkle Root).</li>
<ul>
<li>Version bits.</li>
<li>Input script.</li>
</ul>
<li>Merkle root(TX set/order)</li>
</ul>
<hr style = "height: 5px; visibility: hidden;">
<li style = "font-weight: bold;">Hashes required to achieve target:</li>
<ul>
<li>Example: <span class="inline_code">0x0800...00:</span> Every 2nd Hash...</li>
<li>Example: <span class="inline_code">0x0400...00:</span> Every 4th Hash...</li>
</ul>
<hr style = "height: 5px; visibility: hidden;">
</ul>
</div>
</div><!-- End of 2 column container -->
</section>
<!-- *********** END: Difficulty *********** -->
<!-- *********** Begin: Retargeting *********** -->
<section class = "box">
<div class = "title">
Difficulty <span class = "title weight">Retargeting</span>
</div>
<!-- Derivation Graphic -->
<img src="images/blockchain/retargeting.svg" class = "image" style = "z-index: -1;">
<!-- 2 column container -->
<!-- 45% div for formula and curve--><!-- 45% text & bulletpoint -->
<div class = "multi_text_box_container" style = "padding: 0px 0 0 0; width: 1270px;">
<!-- 45% div for formula and curve-->
<div class = "" style = "width: 60%; font-size: 22px;">
<div style ="text-align: center;">
</div>
</div>
<!-- 45% text & bulletpoint -->
<div class = "text_box"
style = "width: 47%; font-size: 22px; margin: 80px 0 0 0">
<ul style = "margin: 0; padding: 0px; list-style-type: none;">
<li style = "font-weight: bold;">Difficulty Adjustment:</li>
<ul>
<li>Every 2016 blocks.</li>
<li>Adjusted to maintain 10min block interval.</li>
<li>Adjustment maximum bound: 4x.</li>
</ul>
<hr style = "height: 5px; visibility: hidden;">
<li style = "font-weight: bold;">Inflation Bug:</li>
<ul>
<li>Considers interval between 2015 blocks.</li>
<li>Slightly faster block/inflation schedule.</li>
<li>Requires hardfork to fix.</li>
</ul>
</div>
</div><!-- End of 2 column container -->
</section>
<!-- *********** END: Retargeting *********** -->
<!-- *********** Begin: Coinbase *********** -->
<section class = "box">
<div class = "title">
<span class = "title weight">Coinbase</span> Transaction
</div>
<!-- Derivation Graphic -->
<img src="images/blockchain/coinbase.svg" class = "image" style = "z-index: -1;">
<!-- 2 column container -->
<!-- 45% div for formula and curve--><!-- 45% text & bulletpoint -->
<div class = "multi_text_box_container" style = "padding: 0px 0 0 0; width: 1270px;">
<!-- 45% div for formula and curve-->
<div class = "" style = "width: 60%; font-size: 22px;">
<div style ="text-align: center;">
</div>
</div>
<!-- 45% text & bulletpoint -->
<div class = "text_box"
style = "width: 47%; font-size: 20px; margin: 80px 0 0 0">
<ul style = "margin: 0; padding: 0px; list-style-type: none;">
<li style = "font-weight: bold;">Single input script:</li>
<ul>
<li>V1: Arbitrary data.</li>
<li>Beginning V2: Commits to blockheight (BIP30).</li>
<ul>
<li>Coinbase overwriting (identical txid).</li>
</ul>
<li>Up to 100B total.</li>
</ul>
<hr style = "height: 5px; visibility: hidden;">
<li style = "font-weight: bold;">Output script:</li>
<ul>
<li>Witness block:</li>
<ul>
<li>Witness root and coinbase witness commitment.</li>
<li>For witness root: coinbase wtxid = <span class="inline_code">0x00..00<span></li>
</ul>
<li>Non-witness block:</li>
<ul>
<li>No output commiting to witness root required.</li>
</ul>
</ul>
<hr style = "height: 5px; visibility: hidden;">
<li style = "font-weight: bold;">Multiple outputs possible:</li>
<ul>
<li>Fees from transactions.</li>
<li>Block subsidy.</li>
</ul>
</div>
</div><!-- End of 2 column container -->
</section>
<!-- *********** END: Coinbase *********** -->
<!-- *********** Begin: block weight *********** -->
<section class = "box">
<div class = "title">
Block<span class = "title weight"> Size & Weight</span>
</div>
<!-- Derivation Graphic -->
<img src="images/blockchain/block_weight.svg" class = "image" style = "z-index: -1;">
<!-- 2 column container -->
<!-- 45% div for formula and curve--><!-- 45% text & bulletpoint -->
<div class = "multi_text_box_container" style = "padding: 0px 0 0 0; width: 1270px;">
<!-- 45% div for formula and curve-->
<div class = "" style = "width: 60%; font-size: 22px;">
<div style ="text-align: center;">
</div>
</div>
<!-- 45% text & bulletpoint -->
<div class = "text_box"
style = "width: 55%; font-size: 19px; margin: 40px 0 0 0">
<ul style = "margin: 0; padding: 0px; list-style-type: none;">
<li style = "font-weight: bold;">Transaction Weight (BIP141):</li>
<ul>
<li>Weight equals byte size sum of:</li>
<ul>
<li>1 x TX serialised (BIP144, with witness).</li>
<li>3 x TX serialised (Pre-BIP144, no witness).</li>
</ul>
</ul>
<hr style = "height: 5px; visibility: hidden;">
<li style = "font-weight: bold;">Witness Blocks:</li>
<ul>
<li>Maximum weight of 4 Million.</li>
<li>Actual data size depends on witness data ratio in block</li>
</ul>
<hr style = "height: 5px; visibility: hidden;">
<li style = "font-weight: bold;">Examples:</li>
<ul>
<li>TX Data 1000B / Witness Data 0B:</li>
<ul>
<li>TX Weight: 1000 + 3000 = 4000</li>
</ul>
<li>TX Data 1000B / Witness Data 500B:</li>
<ul>
<li>TX Weight: 1000 + 1500 = 2500</li>
</ul>
<li>TX Data 1000B / Witness Data 900B:</li>
<ul>
<li>TX Weight: 1000 + 300 = 1300</li>
</ul>
</ul>
<hr style = "height: 5px; visibility: hidden;">
<li style = "font-weight: bold;">As Witness data size approaches total tx size, <br>effective block size approaches 4MB.</li>
</div>
</div><!-- End of 2 column container -->
</section>
<!-- *********** END: Block weight *********** -->
<!-- *********** Begin: Merkle *********** -->
<section class = "box">
<div class = "title">
<span class = "title weight"> Merkle Root</span>
</div>
<!-- Derivation Graphic -->
<img src="images/blockchain/merkle.svg" class = "image" style = "z-index: -1;">
<!-- 2 column container -->
<!-- 45% div for formula and curve--><!-- 45% text & bulletpoint -->
<div class = "multi_text_box_container" style = "padding: 0px 0 0 0; width: 1350px;">
<!-- 45% div for formula and curve-->
<div class = "" style = "width: 40%; font-size: 22px;">
<div style ="text-align: center;">
</div>
</div>
<!-- 45% text & bulletpoint -->
<div class = "text_box"
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<ul style = "margin: 0; padding: 0px; list-style-type: none;">
<li style = "font-weight: bold;">Merkle Root:</li>
<ul>
<li>Bitcoin256: dsha256 -> LE Encoding.</li>
<li>At each level, duplicate last leaf if uneven.</li>
</ul>
<hr style = "height: 5px; visibility: hidden;">
<li style = "font-weight: bold;">Merkle/Witness Root.</li>
<ul>
<li>TXID leaves -> merkle root (in block header).</li>
<li>WTXID leaves -> witness root (in coinbase output)</li>
</ul>
</div>
</div><!-- End of 2 column container -->
</section>
<!-- *********** END: Merkle *********** -->
<!-- *********** Begin: Subsidy *********** -->
<section class = "box">
<div class = "title">
Block <span class = "title weight">Subsidy</span>
</div>
<!-- Derivation Graphic -->
<img src="images/blockchain/subsidy.svg" class = "image" style = "z-index: -1;">
<!-- 2 column container -->
<!-- 45% div for formula and curve--><!-- 45% text & bulletpoint -->
<div class = "multi_text_box_container" style = "padding: 0px 0 0 0; width: 1270px;">
<!-- 45% div for formula and curve-->
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<div style ="text-align: center;">
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<ul style = "margin: 0; padding: 0px; list-style-type: none;">
<li style = "font-weight: bold;">Genesis Block:</li>
<ul>
<li>50 BTC Block Reward</li>
</ul>
<hr style = "height: 5px; visibility: hidden;">
<li style = "font-weight: bold;">Block reward adjustment:</li>
<ul>
<li>Halves every 210,000 blocks/~ 4 years.</li>
<li>After 33 halvings, block reward is removed.</li>
</ul>
<hr style = "height: 5px; visibility: hidden;">
<li style = "font-weight: bold;">Block subsidy vs fees</li>
<ul>
<li>As block rewards decrease, and usage increases, fee market emerges for block inclusion.</li>
</ul>
</div>
</div><!-- End of 2 column container -->
</section>
<!-- *********** END: Subsidy *********** -->
<!-- *********** Begin: Chain Organisation *********** -->
<section class = "box">
<div class = "title">
Chain <span class = "title weight">Organisation</span>
</div>
<!-- Derivation Graphic -->
<img src="images/blockchain/chain_organisation0.svg" class = "image" style = "z-index: -1;">
<img src="images/blockchain/chain_organisation1.svg" class = "fragment image" style = "z-index: -1;">
<!-- 2 column container -->
<!-- 45% div for formula and curve--><!-- 45% text & bulletpoint -->
<div class = "multi_text_box_container" style = "padding: 0px 0 0 0; width: 1270px;">
<!-- 45% div for formula and curve-->
<div class = "" style = "width: 40%; font-size: 22px;">
<div style ="text-align: center;">
</div>
</div>
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<div class = "text_box"
style = "width: 50%; font-size: 22px; margin: 40px 0 0 0">
<ul style = "margin: 0; padding: 0px; list-style-type: none;">
<li style = "font-weight: bold;">Forks:</li>
<ul>
<li>Different valid blocks of equal height.</li>
<li>All valid blocks are organised by node.</li>
<li>Node follows chain with most POW.</li>
</ul>
<hr style = "height: 5px; visibility: hidden;">
<li style = "font-weight: bold;">Orphan Blocks:</li>
<ul>
<li>Node will request headers/blocks <br>from peers to link to main chain.</li>
</ul>
<hr style = "height: 5px; visibility: hidden;">
<li style = "font-weight: bold;">Checkpoints:</li>
<ul>
<li>Forks below checkpoint not organised into chain.</li>
<li>Does not contribute to security model.</li>
<li>Legacy: Prevent low-difficulty DOS blocks.</li>
<ul>
<li>Resource exhaustion.</li>
</ul>
<li>Currently 13 hardcoded checkpoints.</li>
<ul>
<li>Latest at height 295000.</li>
<li>Forks are costly.</li>
</ul>
</ul>
</div>
</div><!-- End of 2 column container -->
</section>
<!-- *********** END: Chain Organisation *********** -->
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