So far so good enhancing my knowledge and enjoying the courses, great content. Thanks Ivan
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Hi Xav
I think you raise a great point in your question. It seems to me only the courier is protected by the blockchain in this example. You cannot scan a cow so if a statement that the cow was organic you have to trust the farmer to tell the truth in the beginning and then how do you later change the chain if it is found out afterwards that the cow used to be a bodybuilder. I think Ivan commented in one of his streamed daily videos recently that you could also audit the farms cattle feed (he did not use this example but this was the gist of his comment) on other supply chains in order to further establish the farms organic status. But you still get left with the trust issue. I can only assume a way of marking an entry as discredited or false can be used for blocks following the amendment.
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Just going through the course now. I see in the homework sections you have the the maps for each section. The mindmaps are a great way to summarize and visualize all the information. Really useful and helpful. Thank you very much for doing these. Love them 
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@Shashi thereās plenty more where that came from. Help yourself. Or better yet: make your own.
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One solution is to deposit the payment into a temporary āescrowā that is only released when the product is received.
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It was stated that if someone has your private key signature AND your public key, they can verify that the message was sent with your private key. However, Iām just wondering if just having your private key signature would be enough to make this verification- without the public key??
Well so far I love it, first curse is on the books and Iām ready to keep learning and enhancing my knowledge.
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Enjoying the course - it did take me a while to get started-trying to make the most of the CoVID lockdown situation. I must confess however that its still not clear to me how a blockchain not based on a proof-of-worth algorithm works (i.e. proof of stake).
If you send a message with a digital signatures to someone. The reciever must check if this signature is valid on your public key. The signature by itself is useless. you need to use it on a public key to proof that the message is signed by the corresponding private key.
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Thanks a bunch Fabrice!! Excellent videos and explanation!
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In proof of work, people use electricity to fuse blocks together with cryptography. This is a real world cost into a proven secure virtual currency. Proof of stake you use some tokens that is already in that ecosystem as collateral to validate blocks (replace the actual mining costs to validating) if you cheat, you will loose your stake.
Proof of stake is more like some game theory. Playing with human incentives to make it secure. Only proof of work really is connected to real world costs. But in Ethereum, you donāt need overkill on security. It has a total different roadmap for different use-cases than for bitcoin,
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very sophisticated and cool 
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So far great contentā¦ organised systematically. Easy to followā¦ awesome
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So far so good.
This course see and homework is good, it keep me accountable.
Glad i finally started
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Here is a list of people that contribute in developing the bitcoin: https://github.com/bitcoin/bitcoin/graphs/contributors?from=2009-08-30&to=2020-06-27&type=c
You can create a github account and propose a change that will be improved by on of the moderator.
Bitcoin is a decentralized currency. If the developers wanted to increase the total supply of bitcoins, no one would want to update.
Changes in the bitcoin network can always be made, but its up to the miners if they wish to update the changes or stay on the old set of rules. No one controls the bitcoin network.
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I am not sure about tangle but IOTA still uses their coordinator which makes the currency centralized. Not too long ago, this happened: https://www.zdnet.com/article/iota-cryptocurrency-shuts-down-entire-network-after-wallet-hack/
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I am not sure about music but for gaming I really like Enjin. Its pretty cool. It allows you to create your own unique digital assets on the ETH network. It can connect assets into multiple gaming universes. 
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POW (Proof of Work) is not the only consensus used in the blockchain technology. The most popular after POW is POS (Proof of Stake). POS is more game theory, while POW is more connected to the real world. I believe Ivan argues that all excess energy that would be wasted either way can be used to mine bitcoin. Bitcoin does not rely on a location, as long as you have an internet access and the energy by your side you can use it to secure the network. So many places that have excess waste of energy can use it to contribute to the network. 
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Thank you for the great feedback Misael. I agree with you. When I first joined this academy I was blown away by the courses. 
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