Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#3799
  1. Hash functions are functions that create a unique outcome with a unique income.
  2. Hash functions are used in bitcoin to pass transaction information anonymously.
  3. Hash function with more inputs than outputs will necessarily have such collisions, the harder they are to find, the more secure it will get.
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#3800

  1. Hash function outputs a unique calculated fingerprint to unique input data. The idea is that you canā€™t calculate input from output, otherwise the blockchain would break. The security of a blockchain relies on hash functions working properly.

  2. In Bitcoin, the hashing algorithm is used to add new transactions into the blockchain. Input of a function consists of transaction data, timestamps data and reference to the previous block, and the output data needs to meet strict standards. The hash outputs are searched by mining and the strict criterion for the output makes mining of Bitcoin difficult.

  3. Being collision resistant means that the hash functions have to work in a way, that there is no possibility for two or more different inputs to produce same output.

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#3801

  1. Describe hash functions with your own words
    Hash functions creates unique digital fingerprint. These are functions that produces different output on each input. It cannot be reversed.

  2. How are hash functions used in cryptocurrencies like bitcoin?
    In Bitcoin it is used to verify transactions and to create addresses.

  3. What does it mean when we say that hash functions need to be collision resistant?
    Probability of two inputs transforming into same output is impossible.

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#3802
  1. Describe hash functions with your own words

A hash function is data that is encrypted in such a way that is very difficult to solve.

  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 are used to to create private keys

  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).

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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#3803
  1. Hash functions are mathematical equations with an input and an output. One specific input will always produce the same output, but in the SHA-256 algorithm you cannot go from an output to input - if this does occur - consider Bitcoin broken.
  2. Hash functions are used in cryptocurrencies to write new transactions on the blockchain.
  3. When someone says ā€œhash functions need to be collision resistant,ā€ it means that one specific input value always needs to come out with one specific output value. A different input value cannot have the same output as another input value.
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#3804

  1. Hash functions are one-way functions that result in digital fingerprints; and cannot be reversed to find the input. Every unique input results in a unique output.

  2. Hash functions are used to encrypt transaction data into digital fingerprints/mining blocks- which will be used and decrypted by the recipient (miner). This process results in mining and new blocks being added to the blockchain.

  3. Collision resistance = it is difficult to find 2 inputs that can be hashed and will result in the same output.

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#3805

  1. Describe hash functions with your own words
    A hash function is a mathematical function that transforms the input data into a unique data fingerprint that cannot be translated back to the original data. In a hash function, it is possible to go from input to output, but not backwards, thus it provides security.

  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).
    In cryptocurrencies like bitcoin, hash functions are part of the block hashing algorithm which is used to write new transactions into the new blocks of the blockchain during the mining process, where the inputs for the function are the new not-yet-confirmed transactions.

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).
Collision resistance is a property of hash function where one specific output is less possible or impossible to derive from 2 different inputs.

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#3806
  1. A hash function creates an output that canā€™t be reversed to the original input.
  2. In bitcoin hash functions are used to write new transactions into the blockchain so no changes can be made afterwards.
  3. A collision is made when 2 different inputs hash to the same output. A collision resistant hash function is either unlikely to produce this collision or finding such collision is extremely unlikely.
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#3807

  1. a hash function is an encryption of data in fingerprint

  2. any transaction renews hash and save it in blockchain

  3. 2 different hash function canā€™t give the same result

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#3808
  1. hash functions are a one way function that gives a unique digital fingerprint to each transaction, also they can not be solved in reverse eg output ā€”> input
  2. hash functions are used to write new transactions to the blockchain through mining
  3. collision resistant means its difficult (but not impossible) to find two inputs that give the same output
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#3809

  1. A hash function is a function that gives a unique output of a specific length to a unique input of a any length whatsoever in such a way that it is impossible or almost impossible to go reverse, i.e. from output to input.

  2. Hash functions are used in Bitcoin by generating adresses and transactions, and the verication of these.

3.Collision resistance means that it is hard to come up with 2 different inputs that will result in the exact same output.

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#3810
  1. A hash function is one that takes a unique input and provides a unique out put or fingerprint.
  2. In the bitcoin protocol hash functions are used to write new transactions in the blockchain through mining. Bitcoin uses SHA256 which has a one way hash function. You cannot go from output back to an input. This makes Bitcoin robust as otherwise, it would not be secure.
  3. A hash function is collision resistant if it is hard to find two inputs that hash to the same output. If a hash function is not collision resistant then a hacker can break the function with little effort. SHA256 which is used in Bitcoin is collision resistant.
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#3811

  1. Hash functions are one directional computational commands that requires a unique input that generates a unique output, which can be used as a identifier/digital fingerprint.

  2. Hash functions are used to verify/confirm transactions occurring in blocks, as well as serve as both the security and auditing measures of the blockchain.

  3. Collision resistant means it needs to be extremely difficult to have a scenario where multiple unique inputs creates the same output

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#3812
  1. A hash function is a one-way formula that creates a unique (but replicable) output for any given input.
  2. Miners are asked to create a hash from the proposed ā€œblockā€ that needs to be added to the chain. the challenge is to produce the ā€œsimplest??ā€ digital signature, which is random? so they have to try multiple times until you get it. the faster your processing power the more likely you are to get it and be rewarded? (Iā€™m not getting this right yet I think lol).
  3. A hash function is collision resistant when it is hard to find multiple inputs that would produce an identical output. If a hash is not collision resistant then putting in unique data could create none-unique digital signatures so that hash would become ineffective.
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#3813
  1. A function that take a unique input and turn it into a diferent unique output.
  2. To write new transactions into the blockchain. It also gives security to the chain as it is almost impossible to reach to the input transaction.
  3. That it is almost impossible to find 2 inputs that hash to the same output.
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#3814
  1. Hash functions are one way functions where input gives unique output and can not be reversed.
  2. To write new transactions into the blockchain through mining.
  3. A hash function is said to be collision resistant if it is hard to find two inputs that hash to the same output.
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#3815

  1. Hash functions are one way mathematical operations that gets a specific output based on an input.

  2. hash functions are used in cryptocurrencies like bitcoin in mining, security and chaining blocks.

  3. Hash functions should make it very improbable (impossible) for two inputs to have the same hash. For example modding by two would be a terrible hash function because 50% of all numbers would be colliding with each other.

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#3816

1.hash function is one way function that you can only convert input to output and canā€™t convert output to input.
2.hash function can use because it make no one can change the data in blockchain, if you want to change you must convert the output to input and change data input to output again and you will find the out put are completely change, not only change 1 or 2 letter.and the others block will know that and force that problem to the way it was before.
3.collision resistant is it hard to find two inputs that hash to the same output

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#3817
  1. hash function is a mathematical phrase that gatā€™s any string input and provide an output of numbers and letters.
  2. the hash function is used to ahsh the transactions written on the block.
  3. it means that different input will not get the same output.
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#3818
  1. Inputs that create unique fingers prints as outputs, which cannot be reversed (impossible to figure out original input data from output data).

2.BTC uses POW function based on SHA-256 algorithm to reward miners. The mining software needs to hash the blockā€™s header to get it equal or less then a 256-bit alphanumeric code, which all BTC clients share. For each block, there is a hash target value between 0and 256. After the input is entered in the software, a hash is created and randomly provides a number between 0 and 256. So the lower the target value is to create a block, the less likely the hash will be successful and the process will have to be started again.

  1. It means that it needs to be very hard for two different inputs to hash to the same one output.
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