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NODING A BLOCKCHAIN KYLE SIMPSON [email protected]

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Private Databases

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• Read/write access is private • Data is (usually) mutated • Sharing and backups:
 replication • All stakeholders are trusted

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• Private/sensitive data • "Single" point of failure (SPOF) • Target for hacking • Load balancing, eventual
 consistency

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Public Databases

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• Read/write access is public • Data is never mutated • No stakeholders are trusted

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• Public data • Trust based on math • Essentially zero failure • "50% + 1" weakness • Never consistent, consensus
 complications

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What is a blockchain?

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0 1 2 3 A chain of blocks.

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0 1 B22D1D8...89E2B87 BCC29FC...E03F7E0 B22D1D8...89E2B87

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0 1 B22D1D8...89E2B87 { index: 1, hash: "BCC29FC...E03F7E0, prevHash: "B22D1D8...89E2B87", data: ... , timestamp: 1524029051480, }

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{ index: 1, prevHash: "B22D1D8...89E2B87", data: ... , timestamp: 1524029051480, } SHA256( ); // "BCC29FC...E03F7E0" MATH!

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0 1 B22D1D8...89E2B87 BCC29FC...E03F7E0 B22D1D8...89E2B87

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{ index: 1, prevHash: "B22D1D8...89E2B87", data: ... , timestamp: 1524029051480, }

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{ index: 1, prevHash: "B22D1D8...89E2B87", data: ... , timestamp: 1524029051480, } data: [ { hash: "C37AF10...0040A18", data: ... , timestamp: ... , ... }, { hash: "B9DC4FC...91F59BD", data: ... , timestamp: ... , ... }, ... , ], { index: 1, prevHash: "B22D1D8...89E2B87", timestamp: 1524029051480, }

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Timestamps In blockchains, purely informational

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Code!

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Hashes

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Rewrite history? Recompute All Hashes!

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Chaos

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Make recomputation of all hashes in the whole chain "hard"! (aka "not worth it")

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Consensus 50% + 1

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Proof of Work Proof of Stake ...

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"Hard" math problem Solution: brute force "Mining"

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Transactions

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Authorization

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Private Key Public
 Key Asymmetric Cryptography

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Private Key Public
 Key Asymmetric Cryptography

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Private Key Public
 Key "some secret text" Encrypt Decrypt "some secret text" "jn4ra...bBH3/sKn" What I always thought...

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Private Key Public
 Key "some secret text" Encrypt Decrypt "some secret text" "jn4ra...bBH3/sKn" How it actually works...

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Public
 Key Private Key "some public text" Sign Verify "c7/De0...fhJjK3" Digital Signatures ✓

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Node Code!

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github.com/getify/CAF

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NODING A BLOCKCHAIN KYLE SIMPSON [email protected] THANKS!!!!