Blockchain - Sicherheit auch ohne Trust Center

1. 00:00Welcome to the second week of our openHPI course. to blockchain security without Trust Center.
2. 00:08We want to build on that this week, what we discussed last week.
3. 00:14We had looked at the basics of distributed systems, where there's no central instance that everyone trusts,
4. 00:22but where different participants work together and you see, that's pretty challenging to make sure there is, Create trust, ensure that the data is distributed.
5. 00:34We have to expect certain mistakes.
6. 00:36So we looked at this, and then we went back the example of the Byzantine generals, how such a voting process, i.e. such consensus algorithms work,
7. 00:52to make sure that then even joint, in the generals' case, those were joint orders,
8. 00:59otherwise it is the correspondence of the data across the network.
9. 01:04We then continued to look at a data structure, the so-called Linked Timestamping, where it was possible,
10. 01:11various messages in chronological order of their appearance.
11. 01:20We did that with the cryptographic technique of the hash function. and then created a data structure,
12. 01:29where every new message was then hashed away. and from the hash of previous messages and the hash of the newly hashed message.
13. 01:37then another hash value was calculated, so that if you believe the beginning of this chain, even if there's no trust authority,
14. 01:48even if there is no trustworthy timestamp service centrally for the network, all participants know, they can rely on the order.
15. 01:56And then we ended up with the idea, to combine all these techniques, to combine them
16. 02:04and to ask ourselves, for example, if this is true in finance one possibility would be to replace a bank, to make a bank superfluous
17. 02:15and just this exchange of money values to be carried out among the participants
18. 02:21and still give security to the participants, that there really is only money transferred what is available, that since the accounts are managed correctly
19. 02:34and that practically this trust, which is usually provided by the central bank, on algorithms, mathematical algorithms, cryptographic methods can be reached in such a trusted network.
20. 02:50And we want to build on that, because we had seen, this model we had gathered, this cannot be done in practice.
21. 03:02To ensure this voting process, the consistency that even all over the same data layer,
22. 03:08the same account information, there's way too much messaging to be exchanged.
23. 03:16And let's take a look this week. and actually come to the origin of blockchain technology, because it was developed in conjunction with the Bitcoin.
24. 03:28And central idea with this Bitcoin blockchain is the Nakamoto consensus algorithm.
25. 03:38That practically brought the Blockchain into the world at all.
26. 03:43The methods that are brought together in the process, they've been around before,
27. 03:47but this ideal combination, to create a truly relatively effective system, to operate currencies as well,
28. 03:58that's with this application in the area of crypto currency, with the Bitcoin application.
29. 04:08So there is clarified, with which data structures the end user can join such a network as the data structures are, that record the exchange of transactions.
30. 04:21Then we have to deal with how this consensus algorithm, which is central to the constitution of Bitcoin, how it works.
31. 04:33And that's the content of this week.
32. 04:36And then we'll be like this, on last week's preparations,
33. 04:42which shows the Bitcoin in a trusted network, what's possible, a trusting exchange,
34. 04:52the operation of a currency.

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