Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#1366

Digital signatures are created with a help of a private key and an a elliptic curve digital signature algorithm. Is there anything you could point about the hash functions in general? I can see you answered the second and third question correctly. :smiley:

#1367

Exactly. I am glad I could help you understand better. While this is not “critical” to know to understand what bitcoin is and what it presents, it is still very good to know. :slight_smile:

#1368

Hash functions can only hash the data, they can’t encrypt. The main difference between hashing and encryption is that hashing is a one way function while encryption is a two way function. That being said, hash functions are used in bitcoin for security. Do you think you could figure out how exactly do they secure the bitcoin blockhain and its history?

#1369

Almost. Collision resistance means that it is infeasible to find 2 different inputs that will lead to the same output. Determining the input value from the hash is impossible since the hash does not contain any information that could help you reverse it.

In theory there is infinite number of inputs that will produce the same hash. (Don’t let this confuse you, you are still never going to be able to find not even 1 random input that will produce the hash you are looking for.)

I hope all of this makes sense. :smiley:

#1370

All great answers. The only thing I would like to add is that the input for the function does not necessarily have to a string. It can be a number, photo, video or any other data. All of this variations come down to a number, which the hash function will gladly accept and produce a unique hash.

Keep up the great work! :smiley:

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#1371

No worries Daniel. I am glad I could help you understand better. I am here to help you master the technology behind the blockchain and bitcoin. Keep up the great work! :muscle: :muscle:

#1372

  1. Hash functions turn data of different length size to a standard size. The hash function give the data a digital fingerprint.

  2. Hash functions are propagate by your private keys to give data a digital fingerprint that only the recipient can encrypt.

  3. In cryptography collision resistent means that it is hard to find 2 inputs that can be identified by the output.

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#1373

Thank you for the clarification :slight_smile:

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#1374

1.hash functions are bits of code that contain numbers and letters in order to produce an output.
2.hash functions are used in bitcoin by creating new transactions in the blockchain through mining bitcoin.
3.hash functions have to be collision resistant in order to make easy to validate chain against hashes, and also to give a low probability of generating the same output hash.

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#1375

  1. Hash functions are special kind of mathematical functions used in computers where there is a calculation from any given data input to a unique output.

  2. The cryptographic hash function of Bitcoin is particularly important in order to hide the input while it’s possible to rely on the integrity of the data from only reading the output. This is used to have private and public keys in order to securely transact with data.

  3. Collision resistant regarding hash functions means that the output is very unique to any input therefore there cannot be same outputs for different inputs.

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#1376

Answers:

  1. It means a unique output (unique in the sense that there aren’t 2 identical result) is given to an specific input.

  2. Hash functions has multiple usage in bitcoins, and the most important usage is for security. Since hash function provide an unique output. So lets take an account registration for example; when a person input his password into a wallet, that password (input) is immediately churn out into a hash tag (output) and the hash tag is used to store in a block. In the event, if a hacker hacks into the block and retrieve the output, they simply is not feasible to decode the hash tag to deduce the input because it is not feasible to find the value of the input with an output. Other hash functions like hashing every single block in blockchain is another example.

  3. It means that it is unlikely to have 2 identical hash tag (output) on 2 different input. In this sense it means collision resistant.

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#1377

Not in the creation, but in the confirmation of the transaction. Mining is used to confirm and append the transactions to the current blockchain. :slight_smile:

#1378

Hash function that are used in the bitcoin mining are not connected to the private and public keys. They don’t hide anything, transactions in the bitcoin are transperent. Miners mine blocks in order to secure the network by generating a hash according to the current difficulty target. Private key is used to sign a transaction by producing a digital signature. Before miners start adding a transaction in a block they check if the digital signature is valid. :slight_smile:

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#1379

Inserting a password in a wallet will decrypt the private key you own in order for you to be able to sign a transaction. There are no blocks in a wallet. The blocks are added to the blockchain by the miners. Hash functions help us to secure the transactions in the block by producing a hash according to the current difficulty target.

#1380

Thanks for clarifying that! :+1: Really appreciated

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#1381

No problem. I am glad I could help you understand better. Keep up the great work. :muscle:

#1382

My Answers:

  1. Hash Functions are unique inputs that produce an output finger print
    2 Mining
  2. Meaning they don’t have 2 inputs that result in the same output
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#1383

Thank you Mauro for correcting. May I answer it in the form below:

So lets take an account registration for example; when a person generate a private key (input) of a wallet, that private key (input) is immediately churn out into a public key (output) and the public key allows other user to send message or funds to that person. In the event, if a hacker hacks into the block added by miners and retrieve the public key, they simply arenot feasible to decode the public key to deduce the input because it is not feasible to find the value of the input with an output.

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#1384

  1. Describe hash functions with your own words
    Hash Functions are computations that produce/create a unique input to get a unique output, and in no way can’t be done backwards, meaning output to input, its impossible.

  2. How are hash functions used in cryptocurrencies like bitcoin?
    In cryptocurrencies like bitcoin, hash functions are used to create a transactions that are taken as input and run through a hashing algorithm that give us an output of a fixed length. Bitcoin uses
    SHA-256.

  3. What does it mean when we say that hash functions need to be collision resistant?
    Hash Functions need to be Collision resistance because it makes hard to find two inputs that hash to the same output.
    Every hash function with more inputs than outputs will necessarily have collisions.

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#1385

1.- A Hash function is a computational operation that serves to verify if the data that we communicate through a communication network is true or false. Therefore, it serves to verify if the data had been modified on it’s way between “sender A” and “receiver B”.

2.- Hash functions are used in cryptocurrencies like bitcoin as follows : a) As a consensus mechanism among the community of that cryptocurrency which serves to : governance and in the case of bitcoin it serves to agreed which block have the right to access the Bitcoin blockchain.
b) As a unique digital signature. This is used to access to your wallet.
The use of hash functions is at the core of the reason to be of open sources cryptocurrencies, which is a trustless peer to peer system. That, is the greatest breakthrough so far in human communication history… ( Communication is everything , data, money etc ).

3.- It means that it is really hard to find two inputs to arrive to the same output.

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