Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#4540
  1. A hash function is one that encrypts an input with an algorithm and its output is unique with respect to other inputs
  2. The hash function is used in bitcoin to encrypt the information of the blocks that the blockchain has, so when a new transaction occurs, miners must validate the block that has an output hash that begins with a certain number of zeros. The number of zeros is what determines the difficulty of mining, and it varies depending on the hash rate dedicated to the network.
  3. The collision resistant term is when a hash function has a very low probability that n inputs will have the same output value
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#4541

  1. Hash functions are computations that turn inputted data into an alphanumerical output code. Any slight change in the inputted data will result in a new output code. What is unique about a hash function is that the inputted data should not be determinable from the output code.

  2. Hash functions are used in cryptocurrencies in mining. The inputted data is a collection of the most recent transactions of a coin like BTC. Nodes will input this along with their own arbitrary data in order to compute an output in the correct format - for BTC it is currently one that begins with 19 0s. Nodes will compete to find this code, and the winner will be rewarded with some coin.

  3. Hash functions are collision resistant in that it is difficult to find two inputted data values that compute the same output code.

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#4542

  1. Hash functions are known to be very complex, where it involves having one unique input which will produce a unique output. It is also important to note that Hash functions allow one to go from an input to an output but not from an output back to an input.

  2. Hash functions are used in bitcoin for mining and maintaining the blockchain that supports it though a vast network of computers. They are used to create new specific transactions on the blockchain and ensures robust efficiency, anonymity and speed. In addition, there is a digital fingerprint that is created with the hash function.

  3. Collision resistant is referred to creating a function that has a specific input and prevents the same hash from being duplicated through the same hash function. Overall, a hash function is always unique and has uni-directional functionality.

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#4543

Hash Functions ā€¦

  1. Describe hash functions with your own words

A hash function is like a box with two openings. On one end is the opening for the input, on the other end is an opening for the output. The hash function is a specific mathematical formula used within this figurative box to create a desired output. That output can be random or it can be customized depending on what a programmer wants. In the use case of finance, once the hash function is created, it should never be changed so that there can only be one specific input that will always map to the exact same output.

  1. How are hash functions used in cryptocurrencies like bitcoin?

Bitcoin mining is done by repeatedly computing SHA256 hashes. First a private key is generated by using a hash function based on an elliptic curve to create a random 256 bit number, which is then doubled to create a number that is 2 to the 256th power. Then a public key is created by running that number through another elliptic curve hash function. These keys are then linked in the Bitcoin provenance ledger and throughout the consensus network where they are proven and validated. In addition to the private and public keys, a Bitcoin user can also use another hash function to create a unique signature which will only work with the userā€™s private key. Hash functions are used throughout the Bitcoin blockchain. All cryptocurrencies must use some sort of hash function to be made secure and proven to be valid.

  1. What does it mean when we say that hash functions need to be collision resistant?

If a hacker can make two or more inputs map to the same output, this is called a collision. A hash function in which collisions can occur is not completely secure. When a hash function is made collision resistant through cryptography, it cannot be hacked by allowing more than one input to map to an output. Therefore, collision resistant hash functions are obviously very desirable for cryptocurrency.

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#4544

  1. Hash functions are one-way equations that generate a unique ā€˜idā€™/output to every input.

  2. In the Bitcoin protocol, hash functions are part of the block hashing algorithm which is used to write new transactions into the blockchain through the mining process.

  3. A hash function has to be collision-resistant which ensures that it has to be impossible for two different inputs to produce the same output.

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#4545

  1. Hash function is a special function that gives a unique output to a unique input and which cannot be reversed.

  2. Hash function in bitcoin is used to encrypt transaction data and so to secure these data

  3. It means that the output of a hash function canā€™t be the same for two different entries

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#4546
  1. Describe hash functions with your own words
    Hash functions are one way functions -> you can always put an input and get an output. If the input is the same the output will be the same.

QUESTION: what happens when quantum computers go mainstream - in terms of SHA 256?

  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 encrypting transaction all the data on the database. The hash function is SHA 256.

  2. 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 does not get the same output given two different inputs.

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#4547

  1. Describe hash functions with your own words: This is not quite my own words since Iā€™m referencing an authoritative source. But I wanted to be more academic in my responseā€¦
    A one-way hash is a function that takes variable length string and outputs a fixed-length value called a hash value or ā€˜digestā€™. The function is an algorithm that is publicly known. The ā€˜one-wayā€™ nature of the hash function forms the secrecy of the hash. This process takes place without the use of keys. (Harris, Shon, and Maymi, Fernando. CISSP All-in-one Exam Guide. 8th ed. McGraw-Hill, 2018.)

  2. How are hash functions used in crypto currencies like bitcoin? Hash functions are part of the block hashing algorithm used to write transactions into the blockchain during the mining process. The inputs for the function are the recent/not-yet confirmed transactions. (Faife, Corin. Coindesk.com/bitcoin-hash-functions-explained, 2017.)

  3. What does it mean when we say that hash functions need to be collision resistant? Strong hashing algorithms do not produce the same digest for different input strings. If the algorithm does this, it is called a ā€˜collisionā€™. Attackers can attempt to force a collision. This is called a ā€˜birthday attackā€™ (a form of brute force). This is why a hashing algorithm with a larger bit output is less vulnerable to these kinds of brute force attacks; SHA-256, SHA-384, etc. As a result, the hash function is more collision resistant. (Harris, Shon, and Maymi, Fernando. CISSP All-in-one Exam Guide. 8th ed. McGraw-Hill, 2018.)

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#4548

  1. Describe hash functions with your own words
    A: A hash function is a set of mathematical rules that will covert a string of data, no matter how long it is, into an output string of preset length ā€“ for example for SHA-265 the output length is 64 characters in hexadecimal format. Each unique input will produce its own unique output and this output cannot be cracked to obtain the original data.

  2. Q: How are hash functions used in cryptocurrencies like bitcoin?
    A: When a Bitcoin address is created (usually randomly generated), hash functions are utilised to create the private-public key pair of the Bitcoin account as well as the Bitcoin wallet address, plus any subsequent transaction IDs that involve that Bitcoin address.

  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).
    A: Because each unique input results in its own unique output when it is hashed, there should be no chance of a collision where two different inputs generate the exact same output.

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#4549
  1. Describe hash functions with your own words

A hash function is a very complex mathematical process. You give an unique input and the function creates a unique fixed output. It is a one way function so if you have the output it is not possible to recreate 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).

In Bitcoin mining the inputs for the function are all of the most recent, not-yet-confirmed transactions plus some other information like timestamps and the data from previous block.

  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 is near to impossible to mathematicaly create the same output with various inputs so that every input is given an unique output.

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#4550

  1. Hash functions turn certain data into a string of fixed-length output depending on which hash you use.

  2. Hash functions in cryptocurrencies are used to pass transactions anonymously.This functions secures the transaction. It also facilitated to identify these transactions in the blockchain.

  3. The hash functions need to bo collision resistant means that it should be impossible that two different inputs produce the same output.

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#4551

@neuschool, I like your question ā€œwhat happens when quantum computers go mainstream - in terms of SHA 256?ā€ This is the million dollar question that the developers of Bitcoin and Ether need to start working on now, or else they would be playing catch up with the Red-Hat and Black-Hat Hacking Communities.

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#4552

1.hash functions makes bitcoin secure, you gives it a string input , it gives a 256 digital fingerprint.itā€™s oneway,almost impossible to figure from output to input ,easy to from input to ouput.

2.miners use it to generate a output to compare with the target,if itā€™s less than the target ,miners will get the compensation (bitcoin)

3.it means if itā€™s very diffcult to find the same out put with 2 different input then we call the hash function is collision resistance.

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#4553

  1. Hash functions can take any input to create a unique output or fingerprint. You cannot use the unique fingerprint to reverse the process to find out what the original input was.

  2. In cyptocurrencies hash functions are used to create an output fingerprint of fixed length for any data of any length that has been input. For example if you input a single word or an entire sentence, the output would be the same amount of characters. It is also important to note that a single difference in an otherwise identical input will produce a completely different output, although in the same fixed length. You can input with the same sentence twice and change one letter, space, period, anything, and the 2 outputs will look nothing in relation with the exception of the fixed length.

In bitcoin, hash functions are used write new transactions in the mining process. In order for a bitcoin block to be mined, the output must begin with a certain amount of zeroā€™s. Since itā€™s impossible to guess what will create even 1 zero at the beginning of the output, it takes tons of cumputing power running through seemingly infinite input possiblities to mine one block. This keeps the mining of bitcoin slow and steady rather than all at once.

  1. Collision resistance refers to making sure 2 inputs do not produce the same output.
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#4554

1- Hash functions are very complex and each unique input gives a unique output which is like a digital fingerprint. If the hash function is changed in any way then output is also changed - it is not reversible.

2-Hash functions are widely used in cryptocurrency to pass transaction information anonymously.

3-Collision resistance is a property of the hash function in that it is computationally infeasible to find two colliding inputs.

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#4555

  1. hash functions encrypt a file and provide unique set of numbers to identify that file.

  2. the are used to send money over the internet

  3. Collision resistant means it canā€™t be solved by a method less than brute force.

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#4556
  1. Describe hash functions with your own words

A hash function, is a mathematical fingerprinting method which takes an input and produces an output/fingerprint, with the output you can not find out 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).

Bitcoins blocks are based on the previous blocks hash, current transactions. It allows for checking if transaction are actually correct with the information currently on chain

  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 resistant means that you can not get the same output from different inputs. Every unique input had a unique output.

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#4557

1 hash function is a vehicle to encrypt data which creates this digital fingerprint. it can only have an input and an outout normally using the SHA 256 code

2 wow so many uses - security of data , packaging of data, writing more transaction in the blockchain through mining and earning through that.

  1. This terminlogy is to ensure that you cannot destabilise the network/system by having 2 inputs getting the same outcome meaning it is collision restiant for 1 example
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#4558

  1. A hash function takes any string of data, and. provides a unique 256 bit identifier

  2. by creating addresses that are unique and secure

  3. Given 2 different inputs, their respective outputs will guaranteed be different

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#4559

  1. Hash functions provide a means of taking an input and an output that is theoretically impossible to reproduce to reverse and reproduce the input. It creates a digital signature.

  2. Miners use the SHA-256 hash function. Hash functions are used to protect the integrity of data. It is possible to calculate the hash of the data and compare the two values. If they match, then the data has likely not been modified since the original hash was created and is now validated.

  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. Hence the term resistant, it is not impossible to hash two different inputs to the same output but is very hard.

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