09 - Consensus
Wooclap
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Which of the following units is in use for Bitcoin payments?
- Satoshi
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In Bitcoin the block (mining) reward
- WRONG is halved every 105.000 transactions
- is right-shifted every 210.000
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Transaction fee is
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the difference between input and output
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input is always higher than output
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An account address is
- a b58 encoding of pk hash with checksum and version
PoW and hash
- PoW: solve a hard puzzle
- this hard puzzle it is made by a nonce + hash + difficulty
- you must find a value (nonce), a random value that if found must leads to a number beginning with {difficulty}rest_of_the_hash
- how can we optimize finding a good nonce?
- we can’t store the results that starts with 00000 for example if diff=5 because the block header changes everytime
- … but we can if we use a divide et impera approach
- by splitting workload on blocks
- retarget is the action to keep the difficulty more of than equal distributed by blocks, by changing the difficulty once every two weeks (it should takes 20160 minutes)
- ASICS are computers without disks, just memory to evaluates these kind of calculations. They are way less inexpensive for this reason. They need computational power.
- Stale blocks are created when two miners found the solution at the same time
- longest chains are confirmed
- if they have the same chains, then who arrives before