Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#4379

  1. A Hash Function is a way to insert data into a system and generate a unique output, without somebody else having the ability to take that output data and brute force it to get the original input data.

  2. Hash Functions are used to write transactional data into the blockchain, thus encrypting it and keeping the original input data safe.

  3. By saying Hash Functions need to be collision resistant, we mean that it must be very very very hard
    ( but still mathematically possible ) to find different inputs that have the same output.

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#4380

  1. Hash functions are encryption mechanisms that ā€œblanketsā€ a specific output and that ā€œblanketā€ can no longer be taken off once there. This is used to produce identifiers to match the input data to its corresponding output data and retrieve what needs to be retrieved more quickly.

  2. Hash functions are used when an owner of a cryptocurrency coin transfers the coin to the next owner. The previous transaction and the public key of the next owner are hashed (using hash functions) and this hash is digitally signed by the current owner with his/her private key.

  3. Hash functions need to be collision resistant to ensure that a unique hash can be attributed to only one, unique input. Otherwise, authentication will not make sense; tampering can happen. There should ONLY be a one-to-one relationship.

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#4381
  1. Hash function is the function that takes input (data, string) and produces output or hash which is always unique for any given input, there is no way or very hard to retrive the original input from output. Any changes in input will cause completely new output.
  2. Bitcoin uses mining to produce new data blocks, mining process is hashing transaction data by adding new transaction to the old one and adding that data to public ledger - blockchain, there is also a way to create wallet address by hashing public, private keys.
  3. It is almost impossible, or very hard to find two inputs which will produce the same output.
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#4382
  1. Describe hash functions with your own words

A hash function is a function, where you can go from input to output, but never from output to input. The input can be of any size, but the output is a fixed size.

  1. How are hash functions used in cryptocurrencies like bitcoin? (Try to research this on your own, we will cover this later in the course but challenge yourself and see if you can find information on this already now).

Hash functions are used to generate the bitcoin address.

Hash functions are used to write new transactions into the blockchain through the mining process.

  1. What does it mean when we say that hash functions need to be collision resistant? (We didnā€™t use the term ā€œcollision resistantā€ in the lecture, but you will easily find this on Google, we add this question intentionally to make you research information on your own, thatā€™s how you learn best).

It means, that it has to be hard (nearly impossible) to find 2 inputs that give the same output.

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#4383

A hash function is a oneway function from input to output
Hash function is used with the private key (bitcoin adress) to access the information in the blockchain
Otherwise other peopld could guess the private key and change the information

#4384
  1. Describe hash functions with your own words
  • Hash functions are complex equations that take an input and give us a unique output. The output will always be consistent if the same input is entered. The difference between a regular function and a hash function is that you cannot solve for the input if you know the output, so the function only goes one way.
  1. How are hash functions used in cryptocurrencies like bitcoin? (Try to research this on your own, we will cover this later in the course but challenge yourself and see if you can find information on this already now).
  • To solve and log new bitcoin blocks. Itā€™s part of the mining process. Blockchain rewards are distributed when complex equations are solved using hash functions.
  1. What does it mean when we say that hash functions need to be collision resistant? (We didnā€™t use the term ā€œcollision resistantā€ in the lecture, but you will easily find this on Google, we add this question intentionally to make you research information on your own, thatā€™s how you learn best).
  • We mean it must be very hard to find two or more inputs that equal the same output when put through the hash function. The harder ā€œcollisionsā€ like this are to find, the more collision resistant, or secure, the hash function is.
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#4385

Hash functions are not used to derive public keys, for that the elliptic curve function is used. :slight_smile:

#4386
  1. Hash functions are meant to provide a digital fingerprint, a unique identifier for a set of inputs that is not disputable
  2. Hash functions in crypto due to its unique and irreversible output for each input, allows it to be used as an instrument of indisputability, allowing ā€˜smart contractsā€™ between parties with its ā€˜proof of workā€™
  3. Collision resistant means no 2 outputs are the same.
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#4387
  1. A hash function is like a digital fingerprint for a data object. Essentially you put a string on any length in and get a fixed length output. The output for a given string should always be the same (using the same hashing function).
  2. The inputs in to the bitcoin hash function are the most recent none confirmed transactions. The hash is run on this by miners who try to calculate the hash to add the new block to the chain.
  3. Collision resistant means it is statistically unlike to generate the same hash for a different input.
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#4388

  1. Hash Functions are one way functions that compute input information to a unique output code that is considered a ā€œfingerprint.ā€ This output cannot trace back to the input.

  2. Hash functions encrypt the transaction data that is laced into the blockchain.

  3. Each input computes to a unique output, where the probability of two different inputs computing the same output cannot occur.

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#4389

  1. Describe hash functions with your own words
    Hash functions are one way functions that will encrypt given input to output. Output cannot be reversed back to original input. Output is like a digital fingerprint for the input, if even one character or bit is changed in the input the output will be completely different.

  2. How are hash functions used in cryptocurrencies like bitcoin? (Try to research this on your own, we will cover this later in the course but challenge yourself and see if you can find information on this already now).
    Transactions are saved as hashes and private and public keys bitcoin wallet.

  3. What does it mean when we say that hash functions need to be collision resistant? (We didnā€™t use the term ā€œcollision resistantā€ in the lecture, but you will easily find this on Google, we add this question intentionally to make you research information on your own, thatā€™s how you learn best).
    When functions are collision resistant, if it is hard to find two inputs that hash to the same output.

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#4390
  1. Hash functions - Each unique input produces a unique output or digital fingerprints.
  2. Hash functions are used from input to output; however, never from output to input. Itā€™s a one way function.
  3. Collision resistance is a property of cryptographic hash functions: a hash function is collision resistant if it is hard to find two inputs that hash to the same output. Hash function with more inputs than outputs.
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#4391
  • Describe hash functions with your own words

They are a type of function that moves from Input to output creating the same outcome each time as long as all inputed data is exactly the same. However, these types of functions cannot be reversed going from output to input is not currently possible to figure out what the original equation was.

  • How are hash functions used in cryptocurrencies like bitcoin? (Try to research this on your own, we will cover this later in the course but challenge yourself and see if you can find information on this already now).

They are specific type of algorithmic functions used to process transactions through the mining process commonly used in crypto blockchains.

  • What does it mean when we say that hash functions need to be collision resistant? (We didnā€™t use the term ā€œcollision resistantā€ in the lecture, but you will easily find this on Google, we add this question intentionally to make you research information on your own, thatā€™s how you learn best).

It means it is difficult to find the two inputs that hashed to the same output.

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#4392

  1. Describe hash functions with your own words
    Creates a random and unique output for each input. This process can not be reversed. There exists no inverse function to a secure hash function

  2. How are hash functions used in cryptocurrencies like bitcoin?
    By determining the winner of a block. Which means the entity that gets rewarded by creating a new block. Miners have to guess a hash function output = like a lottery

  3. What does it mean when we say that hash functions need to be collision resistant?
    a) You can not find 2 different inputs that produce the same output
    b) For a given x producing h(x) you can not find y which produces h(y) = h(x)

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#4393

1 - A hash function is a one way conversion of input data to output datawith a unique digital fingerprint.

2 - Hash functions are used to encrypt the transaction data, block signatures using a specific 256bit alphanumeric code.

3 - Collision resistant mean that is is highly unlikely mathematically that you would be able to calculate the original input with the hash output.

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#4394
  1. An Hash Function is an input for a unique not reversible digital fingerprint output that we call SHA-256.
  2. Secure & encrypt data, transactions, etc
  3. Collision resistance is the property of a hash function that it is computationally infeasible to find two colliding inputs. This property is related to second preimage resistance, which is also known as weak collision resistance**
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#4395
  1. Hash functions are one-way functions that translate any digital inputs into their own unique digital outputs (digital fingerprints).
  2. Hash functions are used to run consensus mechanism, to add blocks in chains and they are key functions in Bitcoin mining.
  3. There can never be two of the same output from the hash functions. Hash functions need to ā€˜resistā€™ from duplication of output i.e. ā€˜collisionā€™.
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#4396
  1. Describe hash functions with your own words

Hash functions are one way functions. The input gives you a fingerprint of the input = output. From the output you cannot recover the input.

  1. How are hash functions used in cryptocurrencies like bitcoin? (Try to research this on your own, we will cover this later in the course but challenge yourself and see if you can find information on this already now).

They are used to power the Proof of Work consensus that validate transactions on the blockchain

  1. What does it mean when we say that hash functions need to be collision resistant? (We didnā€™t use the term ā€œcollision resistantā€ in the lecture, but you will easily find this on Google, we add this question intentionally to make you research information on your own, thatā€™s how you learn best).

It means that if it is hard to find two inputs that hash to the same output

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#4397

  1. Hash functions is the process of taking some specific data or input that produces a very specific output for that data

  2. With cryptocurrencies, hash functions take some data/input and maps it to an output of some fixed size; resulting in a cryptographic output of a string of data of a specific length that is irreversible

  3. A hash function is collision resistant if it is hard to find two inputs that hash to the same output. No two inputs should produce the same output, therefore not having a unique signature specific to that input (the hashing algorithm makes this very hard to do)

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#4398

  1. Hash functions generate a unique fixed size digital fingerprint from a given input of any size. It is also a one-way function meaning that thereā€™s practically no way of figuring out the input from the fingerprint.

  2. In bitcoin, the SHA-256 function is used to generate the transaction id and also in the mining process to write new transactions to the blockchain.

  3. Collision resistant means that the hash algorithm should make it difficult to find two messages (or two different inputs to the hash function) that result in the same hash. If itā€™s not, one message could be swapped for another without changing the hash.

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