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I'm reading papers since hours and still don't get one thing: A bitcoin transaction is an information like "Bob sends 2 BTC to Alice". This message is signed with Bobs private key and needs to be added to the blockchain that is distributed to every participant. I also got that you need to calculate a Proof of Work to be able to add something to the chain. Or in other words: The other participants won't accept your block without the proof of work.

How does Bob get this proof of work or how does Bobs message went to a person who has such I proof? I can't believe that every person making a transaction needs to calculate it's own proof. Is it really like that? If not: How does Bobs "message" is transmitted to a person who owns such a proof, how can the person make sure that Bobs message is a valid transaction (and not only garbage) and what the motivation for this person to process Bobs message at all?

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How does Bob get this proof of work or how does Bobs message went to a person who has such I proof?

Bob offers a fee to whoever attaches his transaction to a block with the necessary proof of work. Now Bob wants to get his transaction to someone who can attach it and people who generate proof of work want Bob's transaction so they can get the fee.

When two people each want to communicate with each other, there is no difficulty in arranging that communication. We have the Internet.

I can't believe that every person making a transaction needs to calculate it's own proof. Is it really like that?

No. Those who want to execute transactions offer a fee to those who calculate proof of work. This is a mutually beneficial arrangement.

If not: How does Bobs "message" is transmitted to a person who owns such a proof,

Over the Internet.

how can the person make sure that Bobs message is a valid transaction (and not only garbage)

They just check to make sure whether it follows all the rules, which everyone knows. If so, it's valid. If not, it's invalid.

and what the motivation for this person to process Bobs message at all?

They want to make as much money as possible for the proof of work they provide. So they actively search for the transactions that offer the highest fees to them.

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As a rough quick answer for any Blockchain not just Bitcoin..

-users authenticate their transactions with Cryptographic signatures, and submit a transaction Fee

-Transactions reside in the mining pool for miners to select usually thru an auction where fees r considered like bids, the auction format may differ from one Blockchain to another

-Miners verify the signatures of TXs upon selection, and collect the fees+block reward if the block was approved.

Here's a few diagrams from my early days in cryptocurrency, can't remember the source video

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Ps

  • The word "Encrypting" in the images is not quite accurate, what is done is digitally signing using a public-private key Encryption Algorithm (elliptic curve in Bitcoin & many cryptocurrencies) -Transactions remain publicly readable to the miners in the mining pool (unless something called "commit-then-reveal" scheme is used to deliberately hide the content of a TX from the miners thru encryption)
  • Checking the authenticity means verifying the correctness of the digital signature

The source of the figs https://youtu.be/E2JRnFgrztM ( with only the clarifying red & blue text added by me after the comments) It was like my first let's get an idea and see if it worth further study & research

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    This series of graphics is incorrect and misleading in several ways: 1. Bitcoin transactions are not encrypted. In fact the Bitcoin protocol does not use encryption anywhere at all. Transactions have cryptographic signatures, which authenticates their content as being issued by the private key holder, and protects them from being changed. – Murch Jun 26 at 16:41
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    2. Miners don't "verify the authenticity of sender and receiver". All nodes (of which miners are a subset) verify that the transaction is well-formed and valid. The signatures in the inputs attest to the owner of the funds having signed off, the only check for the receiver is whether the output script is valid. – Murch Jun 26 at 16:42
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    3. "The transaction would show that bitcoins are reduced from one wallet, and added to another." ⇒ Wallets don't exist as a construct in the Bitcoin protocol. A transaction consumes and creates Unspent Transaction Outputs. – Murch Jun 26 at 16:45
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    4. Not sure what the last slide has to do with the topic. It seems to reference the oracle problem. – Murch Jun 26 at 16:46
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    Anyway, the text in your answer is much better than the graphics which are not just oversimplified but wrong. I suggest removing the images. – Murch Jun 26 at 16:49

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