Blockchain Technology In the U.S. Government by Michael Erbschloe - HTML preview

Table of Contents

182 Executive Summary ..................................................................................................... iv

183 1 Introduction ............................................................................................................ 9

184 1.1 Background and History.................................................................................. 9

185 1.2 Purpose and Scope ...................................................................................... 10

186 1.3 Notes on Terms ............................................................................................ 10

187 1.4 Document Structure...................................................................................... 10

188 2 Blockchain Architecture...................................................................................... 12

189 2.1 Hashes.......................................................................................................... 12

190 2.2 Transactions ................................................................................................. 13

191 2.3 Asymmetric-Key Cryptography ..................................................................... 13

192 2.4 Addresses and Address Derivation............................................................... 14

193 2.4.1 Private Key Storage............................................................................ 14

194 2.5 Ledgers......................................................................................................... 15

195 2.6 Blocks ........................................................................................................... 19

196 2.7 Chaining Blocks ............................................................................................ 23

197 3 Blockchains in Operation.................................................................................... 23

198 4 Consensus............................................................................................................ 26

199 4.1 Proof of Work Consensus Model .................................................................. 26

200 4.2 Proof of Stake Consensus Model ................................................................. 29

201 4.3 Round Robin Consensus Model ................................................................... 30

202 4.4 Ledger Conflicts and Resolutions ................................................................. 30

203 5 Forking.................................................................................................................. 33

204 5.1 Soft Forks ..................................................................................................... 33

205 5.2 Hard Forks .................................................................................................... 33

206 5.3 Cryptographic Changes and Forks ............................................................... 34

207 6 Smart Contracts ................................................................................................... 35

208 7 Blockchain Categorization .................................................................................. 36

209 7.1 Permissioned ................................................................................................ 36

210 7.1.1 Application Considerations for Permissioned Blockchains ................. 36

211 7.1.2 Use Case Examples........................................................................... 37

212 7.2 Permissionless.............................................................................................. 38

213 7.2.1 Application Considerations for Permissionless Blockchains............... 38

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214 7.2.2 Use Case Examples........................................................................... 38

215 8 Blockchain Platforms .......................................................................................... 40

216 8.1 Cryptocurrencies........................................................................................... 40

217 8.1.1 Bitcoin (BTC) ...................................................................................... 40

218 8.1.2 Bitcoin Cash (BCC) ............................................................................ 41

219 8.1.3 Litecoin (LTC)..................................................................................... 41

220 8.1.4 Ethereum (ETH) ................................................................................. 41

221 8.1.5 Ethereum Classic (ETC)..................................................................... 41

222 8.1.6 Dash (DASH)...................................................................................... 42

223 8.1.7 Ripple (XRP) ...................................................................................... 42

224 8.2 Hyperledger .................................................................................................. 42

225 8.2.1 Hyperledger Fabric............................................................................. 42

226 8.2.2 Hyperledger Sawtooth........................................................................ 43

227 8.2.3 Hyperledger Iroha............................................................................... 43

228 8.2.4 Hyperledger Burrow............................................................................ 43

229 8.2.5 Hyperledger Indy ................................................................................ 43

230 8.3 MultiChain..................................................................................................... 43

231 9 Blockchain Limitations and Misconceptions..................................................... 44

232 9.1 Blockchain Control ........................................................................................ 44

233 9.2 Malicious Users............................................................................................. 44

234 9.3 No Trust ........................................................................................................ 45

235 9.4 Resource Usage ........................................................................................... 45

236 9.5 Transfer of Burden of Credential Storage to Users....................................... 46

237 9.6 Private/Public Key Infrastructure and Identity ............................................... 46

238 10 Conclusions.......................................................................................................... 47

239

240 List of Appendices

241 Appendix A— Acronyms ............................................................................................ 48

242 Appendix B— Glossary .............................................................................................. 50

243 Appendix C— References .......................................................................................... 55

244

245 List of Tables and Figures

246 Table 1: Examples of Inputs and SHA-256 Digest Values ............................................ 12

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247 Table 2: Example Transaction....................................................................................... 13

248 Figure 1 - A simple network maintaining a copy of a ledger across nodes.................... 16

249 Figure 2 - Submitting a Transaction to a Node, waiting in the Pending Transaction List

250 ............................................................................................................................... 17

251 Figure 3 - Transaction 4 information transmitted from node to node............................. 18

252 Figure 4 - Transaction 4 has been included into a block, nodes are transmitting the

253 information; the final node has not yet received the latest information................... 19

254 Figure 5: Example of a Merkle Tree .............................................................................. 21

255 Figure 6: Blockchain with Merkle Tree .......................................................................... 22

256 Figure 7: Generic Chain of Blocks................................................................................. 23

257 Figure 8: Transaction Being Added to Unspent Transaction Pool................................. 24

258 Figure 9: Finalized Block (Generalized) ........................................................................ 25

259 Figure 10: Distributed Network in Conflict ..................................................................... 31

260 Figure 11: Blockchains in Conflict ................................................................................. 31

261 Figure 12: Chain B Adds the Next Block ....................................................................... 32

262 Table 3: Impact of Quantum Computing on Common Cryptographic Algorithms .......... 34

263