Homework on Consensus - Questions

Blockchain and Bitcoin 101
#1891

1/ Consensus in Blockchain refers to the mechanism of agreement between all the computers. When all verify that input data is the same, consensus can be reached and the information is included as fact (or true).

2/ A central database can be amended or corrupted by the controlling organisation and therefore we have to rely on them telling us the truth.

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#1892

1.) blockchain will only accept the truth, the network is incentive to ensure each transaction is correct and not false

2.) central databases, rely’s on the reputation of the owner, and controls in place to ensure there is no tampering as we have seen over and over again on data loss prevention, that hackers and companies who own the data are unable to secure and prevent tampering

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#1893
  1. What does it mean when we say that in blockchain, consensus determine the truth?

Because each node in the network needs to agree on the integrity of the information on chain, if a node has a corrupt copy of the blockchain other nodes will discard it and accept the chain that has reached consensus, usually the longest.

  1. How is this different from how truth is determined in a central database?

In blockchain all nodes can be a source of truth and need to come up to a consensus, which is a democratic process on agreeing which data is the truth. On a central database there is only one source of truth.

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#1894
  1. In blockchain, the truth is determined by the fact that information across the blockchain network is the same - each node holds the same information. If the transaction is in agreement with information held, then it is accepted. If not, it won’t be verified.
  2. In a centralized database, there is one overriding authority, which determines whether something is true or not. No consensus is required.
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#1895

1 If (at least 51%) the network agrees A is true, then A is incorporated in the BC. If less agree, there is no consensus and A will not be added to the BC database.
2 A central database will find any statement valid for entry ( there might be some restrictions) and the truth is what the owner decides.

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#1896
  1. The ledgers/miners decides the truth when they agree. And they have a financial incentive to be honest.
  2. In a central database one individual or institution can decide and change the truth.
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#1897
  1. What does it mean when we say that in blockchain, consensus determine the truth?
  2. How is this different from how truth is determined in a central database?
  1. In blockchain no one single entity have power to verify a transaction. The whole network of computers have to agree and ensure its genuineness. If someone try to send a false data to a network, they might get through one or few networks but it is literary impossible to successfully cheat the whole network. So, consensus that determine the truth, is the key for secure network.
  2. In a central database a transaction can be removed, modified, altered. This doesn’t require the whole network consensus while a blockchain does need such. We cannot be so sure about how truth is determined in a central database is trusted.
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#1898

  1. All participants need to agree whether information/ data being added to the blockchain
    are correct/truth. All participants being incentive.

  2. Central Database can be manipulated by anyone who gains access to it for their own
    personal motives.

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#1899

  1. It means that we know the given transaction or data is true or valid, if it has been verified and agreed upon by the network of computers.

  2. In a centralized database a transaction or data is agreed upon by that database alone. Whoever controls the database controls the truth.

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#1900

  1. All participants are agreeing on the truth without trusting each other.

  2. Consensus is decentralised and incentivised to determine the truth.

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#1901

[quote=“ivan, post:1, topic:8425, full:true”]
Homework on Consensus - Questions

  1. What does it mean when we say that in blockchain, consensus determine the truth?

Consensus determines the truth in blockchain by multiple nodes verifying the data. If all nodes do not agree the data is correct and true, the entry on the blockchain will be ignored.

  1. How is this different from how truth is determined in a central database?

We are putting trust into an entity to provide correct information. We may not often be able to verify this data. For example a supermarket selling clothes may tell customers that the material is high quality when in fact it is from a cheap and nasty supplier that support child labour.

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#1902
    1. What does it mean when we say that in blockchain, consensus determine the truth?

it is only when all verifying parties agree that consensus is determined, hence truth established. no consensus can be achieved if one verifying party disagrees.

    1. How is this different from how truth is determined in a central database?

in a central database, whatever party that has the authority over the database establishes the “truth”. all other players involved have to deposit their trust on this authority.

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#1903

On the blockchain 100% consensus must be reached. If even one node disagrees it would mean it could fork from the rest of the network :slight_smile:

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#1904

  1. Via a network of computers a consensus is reached by all agreeing using incentives and a mechanism such as POW or POS

  2. Truth on a central database is dependent on the input only.

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#1905

What do you mean by that? What input in particular?

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#1906

When you say it could fork, that means it doesn’t have to? I mean if the whole network needs to agree, does that mean there are more iterations of checking? Some form of round table discussion :smiley:

#1907
  1. It means that people are working and getting paid in order to say the truth, so for example if there is a hacker trying to manipulate something, the other “workers” will immediately recognize this and ignore it. Not allowing the transaction to continue. The chain can not changed at any point and every time a new transaction is added it increases the security of it, making it impossible for anyone to cheat. When a transaction is being processed, everyone verifies that it is legitimate and they allow it to go through. At the end of the day everyone wants to make money and with Blockchain they will make it by following the process, not by trying making fun of it.
    I personally believe this is amazing because it motivates people to do the right thing in order to get a reward, and not like on the daily basis that if you do the illegal things you will get more money than by doing the legal ones.
  2. Because you don’t trust they are saying the truth, you verify.
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#1908

In the bitcoin source code there are specific steps each node executes for every transaction it receives to verify its valid. If for example one would change the source code to make some transactions that are not part of these rules valid, other nodes would reject it.
If then this specific node would be so stubborn to also mine blocks with these transactions, all other nodes would reject it thus making a split in the chain or fork :slight_smile:

3 Likes
#1909
  1. Because nodes validate if information is true or not.
  2. In central database is some kind of authority which can alter database
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#1910
  1. the network collectively agrees to the correctness of the transaction
  2. central authority decides the truth. There is room for manipulation with this system.
1 Like