Blockchain Cryptography
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Introduction to Cryptography by Blockchain Workspace
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Blockchain Cryptography
- 1. Blockchain Workspace www.blockchainworkspace.com 1 Why Cryptography?
- 2. Blockchain Workspace www.blockchainworkspace.com 2 Blockchain - Why Now?
- 3. Blockchain Workspace www.blockchainworkspace.com 3 Be one of them?
- 4. Blockchain Workspace www.blockchainworkspace.com • disconnected • not taken seriously ever again • vulnerable Daddy and Facebook 4
- 5. Blockchain Workspace www.blockchainworkspace.com 5 Homework Assignment Home work sent in: • Explain in your own words what the difference is between symmetric and asymmetric encryption • explain which “form” is used mostly in bitcoin and why!
- 6. Blockchain Workspace www.blockchainworkspace.com 6 How do you find the right places?
- 7. Blockchain Workspace www.blockchainworkspace.com 7 How do you get them?
- 8. Blockchain Workspace www.blockchainworkspace.com 8 How do you get rid of them?
- 9. Blockchain Workspace www.blockchainworkspace.com 9 Roles & objects Source: Blockchain Workspace; CC by SA
- 10. Blockchain Workspace www.blockchainworkspace.com 10 Beginning of the end of security English letter frequency
- 11. Blockchain Workspace www.blockchainworkspace.com Hashing 11 Hash function: 1. Takes any digital input Fixed size output (256 bits) efficiently computable 2. Security properties: collision free hiding puzzle-friendly
- 12. Blockchain Workspace www.blockchainworkspace.com Source: Blockchain Workspace CC by SA Feature 1 of 3: Collisions exist, but unfindable 12
- 13. Blockchain Workspace www.blockchainworkspace.com Applications of Hashing properties 13
- 14. Puzzle Friendliness Applications of Hashing properties Blockchain Workspace www.blockchainworkspace.com 14 Source: Scott Richard CC BY SA, see original
- 15. Blockchain Workspace www.blockchainworkspace.com 15 Assignment Proof of Existence • a masterpiece poem about bitcoin (2 minutes) • proof of existence tool (1 minute) • proof of existence that your poem existed today (3 minutes) • proof to your neighbour that this poem already existed (2x2 minutes)
- 16. Blockchain Workspace www.blockchainworkspace.com Hiding, puzzling & colliding? Source: Blockchain Workspace; CC by SA
- 17. Blockchain Workspace www.blockchainworkspace.com Source: Blockchain Workspace; CC by SA Hashpointer e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
- 19. Blockchain Workspace www.blockchainworkspace.com 19 Symmetric versus Asymmetric Encryption
- 20. Blockchain Workspace www.blockchainworkspace.com Source picture: stackexchange.com ; CC by SA, see original creator Digital Signatures - easy
- 21. Blockchain Workspace www.blockchainworkspace.com 21 Digital Signatures - extended Source picture: https://staging.signinghub.com/electronic-signatures/Source picture: Blockchain Workspace
- 22. Blockchain Workspace www.blockchainworkspace.com 22 Public/Private Keys for Identity Source: Princeton University / Coursera: Introduction to Crypto and Cryptocurrencies
- 23. Blockchain Workspace www.blockchainworkspace.com 23 Principles Modern Cryptography Core principles of Cryptography 1. Definitions Exact, mathematical model and definition of crypto ‘security’ 2. Assumptions Clearly stated; no double interpretation 3. Proofs of security
Editor's Notes
- What is the real need to use this knowledge. How can you actually use this knowledge.
- Repeat of essence of first 1.5 hours Encryption {key} Timestamping and consensus {stamp} Verification {check} Where is the accidental discovery? Where is the dissatisfaction in the customer group? Do you recognize the Me-too within your own branche?
- [Beamer off] Sign: Cryptographic Hash Functions - <thumb> Sign: Hash Pointers and Data Structures - <pointing finger> Sign: Digital Signatures - <Air sign> Sign: Public Keys as Identities - <‘ME’ on forehead> Sign: Chain - <grip hands>
- One uniquely identifiable person … -> virtual identity (public address) & multi-sign options. Why: because your public address gives you worldwide transparency about your virtual identity, while your private key gives you control.
- Each convertor has KYC obligations. There are “tiers” or “tranches” Localbitcoins: barter trade on a local level
- Check for valid bitcoin addresses that only you control! bitaddress.org
- kraken, litebit.eu, poloniex etc. you can convert back to many currencies and transfer it back to your old (reliable?) bank account.
- <ask: what kind of attacks are possible?> Roles, objects & ATTACKS: plain text, cipher text, key [Beamer on] <Review + Assignment focus> [Beamer off] <Before assignment DIY One Time Pad>
- Concluding assignment DIY One Time Pad You need a good source of randomness for your keys
- <So which primitives do we need to develop means of safe store and exchange of value? What extended features features should cryptographic primitives have?> We need more security, we need better usability, more efficiency and self sovereigned privacy? Sign: Cryptographic Hash Functions - <thumb> Sign: Hash Pointers and Data Structures - <pointing finger> Sign: Digital Signatures - <Air sign> Sign: Public Keys as Identities - <‘ME’ on forehead> Sign: Chain - <grip hands> <Exercise: 3 groups -> think of the properties of Cryptographic Hash Functions, 1. explain how it should work, 2. think of an application >
- By Scott Richard CC BY SA. See Original: https://www.flickr.com/photos/32029534@N00/23502453065
- Assignment Get your phones, create a masterpiece poem about bitcoin (2 minutes), search with Google for proof of existence tool (1 minute), proof of existence that your poem existed today (3 minutes), proof to your neighbor that this poem already existed (2x2 minutes) What did you learn? Payment of a service fee -> takes too much time The smallest error…. https://notbot.me https://proofofexistence.com/
- Which two very important features in one go? <hash+pointing> Why should we care? This is the Chain-trick, the data-minimising trick, the hiding trick, the access management trick in blockchain techniques. The inner working becomes clearer to us -> later.
- Hashpointer -> hash that points to data and validates it Log N validation times No circular chains allowed / possible Which of the following changes can be detected in a blockchain data structure? Adding a block, removing a block, modifying data in a block, changing the order of blocks. Answer: all.
- What is the difference & why should we care? symmetric algorithms: (also called “secret key”) use the same key for both encryption and decryption; asymmetric algorithms: (also called “public key”) use different keys for encryption and decryption.
- https://bitcoin.stackexchange.com/users/307/deathandtaxes What do we need to make it work? Think of cryptography. Is this an example of symmetric or asymmetric cryptography?
- <Which two very important features in one go? <hash/Digest+privkey_encryption> Why should we care? Various Proofs: Identity, Existence, Location, Ownership etc. Fun trick: sign a hash pointer. Bitcoin: ECDSA: Elliptic Curve Digital Signature Algorithm
- Useful tricks: 1. The public key IS the Identity, the private key PROOFS the Identity (Authentication) 2. Decentralised key generation: anyone can make a new identity at any time and as many as you want. These identities are called ADDRESSES in bitcoin.
- Proofs given an guarantee of security, …. only RELATIVE TO Definitions and Assumptions Provable secure schemes can be broken! If: a. definition does not correspond with reality b. assumption is invalid