Homework on Hash Functions - Questions

[Anthrax-the-clown]

1. Hash functions are unique one way functions where each individual input creates a digital fingerprint (output).

2. With Bitcoin the hash function is used to create a hash transaction. This transaction hash code is unique to that individual block of data.

3. A hash function is collision-resistant if it is hard to find two inputs that hash to the same output. Basically two different inputs could not produce the same output (in this case the hash).

[OlgaB]

1. Hash functions are used for generating a unique fixed length output (hash) based on a unique input (random length).
2. Based on mining process, new blocks need to be created and added to the blockchain. In order to do so, miners need to find a hash that meets the target difficulty.
3. Collison resistance reffers to hasf function property of avoiding that two different inputs generate the same output (hash). If it happens, the function is not secure.

[marius]

1. Hash functions encrypts input to produce output, depending of used functions is hard to trace back input to the output.

2. In BTC has functions are used to add to transitions to the blockchain.

3. Collision resistant means that it will not provide same never provide same output for two different inputs.

[Alexandros_Ntolgkov]

1. Hash functions are a way of securing the information that you enter into the blockchain. Every time that you add unique information or data into the function as input, you get a unique output of numbers and letters to serve as the ID of the data that you inserted and this is one way only as to guess the hash function number would be equal to winning the lottery and it can be used as an integrity check. If you would alter even the smallest thing in the string of data that you entered, then the whole hash function would be entirely different.

I suppose - and this can be completely wrong - each bitcoin transaction when inserted into the blockchain produces its own unique ID hash output which the miners afterwards have to guess through proof of work in order to validate the transaction. After this transaction is validated and added into the blockchain each block uses its reference for the previous block.

2. Okay so after researching, that was wrong! As I understood it now is that each transaction of BTC has its own unique bitcoin function ID but what the miners do is they simply collect the validated transactions and create a hush ID for the whole bunch of them! Then, they create a second one to mention for the previous block except for the genesis block since it has nothing to refer back to.

3. Collision resistant means that each input will have its own unique hash ID verification.

[CMar10]

1. A mathematical function that converts data input into a hash value.
2. Transactions are used as input and run through the hashing algorithm to create a hash value.
3. Collision resistant means that no two inputs can create the same output.

[asvpxroland]

1.) A hash function is an input of data of any form and size and translates it to an output data of a fixed size.

2. When mining bitcoin, the input functions represent the most recent transactions that are not yet confirmed. In order to be rewarded with bitcoin you need to put in the largest amount of work to solve a block - by doing so you’re locking in all of the newest transactions into a block, which is added to the permanent record of all previous transactions forming the “blockchain”.

3. A hash function needs to be collision resistance because it means it is harder (but not impossible) to find the output digest from a different input.

[AndrewM]

1. A hash function takes information (input) and gives it a unique digital fingerprint (output). This function only works one direction so that the fingerprint (output) cannot be used to find the input.
2. Hash functions are used in cryptocurrency to write new transaction to the blockchain through the mining process.
3. Collision resistant means an attacker can’t find two inputs that map to the same output.

[Richieloco]

1. Hash functions are formulas that give a unique output for every unique input. You can only go form input to output. You shouldn’t be able to go from output to input or else that means this hash function can be hacked.
2. They make it so that things like Proof of Work concepts can’t be worked backwards or hacked
3. For a hash function to be collision resistant it means that no two unique inputs should ever have the same output

[Saguzi]

1. A hash function allows you to get a digital fingerprint of an input. It’s highly improbable to be able to
   find what the input was based on its fingerprint.

2. Hash functions are used in Bitcoin to store transactions into the blockchain through mining.
   Transactions are run through a hashing function to produce a specific output. If transactions are
   hashed correctly it is then added to the blockchain.

3. Hash function can have only 1 unique input. If 2 different inputs result in the same hash then there is
   a ‘collision’. Collision resistance reduced the chance of this happening.

[JQTrxxx_Au2151]

1. Hash is the encryption used to protect and make data more secure.
2. Write new transactions into the blockchain through the mining process.
   3.It’s hard to find two inputs that give the same hash.

[5haman]

1. Describe hash functions with your own words.

Hash functions are a subdomain of cryptographic functions which give a unique output when given a specific input. There are more and less secure hash functions, BTC uses SHA256 (veeeeeery secure).

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).

Hash functions are used for many reasons when it comes to Bitcoin, in fact, the whole blockchain is littered with hashes. Each block includes the hash of the previous block, and that is how the chain of blocks is formed. Miners use hashing to add successfully mined blocks to blockchain.

3. What does it mean when we say that hash functions need to be collision resistant? (We didn’t use the term “collision resistant” in the lecture, but you will easily find this on Google, we add this question intentionally to make you research information on your own, that’s how you learn best).

‘‘Collision resistant’’ is a term in cryptography which relates to hash input and output values, in particular, it speaks of a scenario where two inputs would generate the same hashed output. The probability of this occurring is so tiny that for the sake of keeping it simple - we can say that it is almost impossible. Which is why is is called ‘‘resistant’’ to collision.

’‘If your dreams don’t scare you - they aren’t big enough!’'

[Sharon]

1. Describe hash functions with your own words
   Hash functions give input a unique fingerprint as output in the form or a string of letters and numbers. If the input is changed even slightly, the output changes completely. For the hash function to be secure it can only create output from input and not vice-versa.
2. How are hash functions used in cryptocurrencies like bitcoin?
   Hash functions are part of the block hashing algorithm which allows miners to write new transactions to the blockchain. Bitcoin mining takes new transactions as the input, along with some administrative data such as timestamps, a reference to the previous block, and some of their own arbitrary data and creates output hash. To ‘solve’ a block the input must be altered and hashed until a hash starting with 18 zero’s is derived as output.
3. What does it mean when we say that hash functions need to be collision resistant?
   There should never be one output that is derived from two unique inputs. The output should always be unique to each input.

[theDurkleton]

1. Describe hash functions with your own words

• a hash function is a mathematical formula for turning any file or string or dataset into a unique code or digital fingerprint that cannot be reversed to find the input.

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).

• All the transactions that go into the blocks are hashed before they are put into the block.

3. What does it mean when we say that hash functions need to be collision resistant? (We didn’t use the term “collision resistant” in the lecture, but you will easily find this on Google, we add this question intentionally to make you research information on your own, that’s how you learn best).

• For a hash function to be collision resistant it means that there is no way for two different inputs to produce the same hash.

[Misha14]

1. Describe hash functions with your own words
   Function that creates a unique output of a given input that cannot be reverse
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).
   A cryptographic hash function is an algorithm that takes an arbitrary amount of data input—a credential—and produces a fixed-size output of enciphered text called a hash value, or just “ hash .” That enciphered text can then be stored instead of the password itself, and later used to verify the user.
3. What does it mean when we say that hash functions need to be collision resistant? (We didn’t use the term “collision resistant” in the lecture, but you will easily find this on Google, we add this question intentionally to make you research information on your own, that’s how you learn best).
   if it is hard to find two inputs that hash to the same output makes it unique and secure

[Cero]

1. Describe hash functions with your own words
   Hash functions are cryptographic functions which transform any given written data (input) into hash phrase (output), composed from numbers and letters.

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).
-Storing passwords: When you create an account where you store for example cryptocurrency, your pasword is changed to hash.
-Creating a block onto blockchain with hashing (miners)
-Basically whole blockchain is hashing-every additional block is hashed by the previous one.

3.What does it mean when we say that hash functions need to be collision resistant? (We didn’t use the term “collision resistant” in the lecture, but you will easily find this on Google, we add this question intentionally to make you research information on your own, that’s how you learn best).
In cryptography collision resistance is a property of cryptographic hash functions( a hash function H is collision-resistant if it is hard to find two inputs that hash to the same output; that is, two inputs a and b where a ≠ b but H (a) = H (b). It means that any hash function with more inputs than outputs will necessarily have such collisions the harder they are to find, the more cryptographically secure the hash function is.

[Vinicius_Libero]

1, Hash Functions are one way functions which transform input data into unique output that is almost impossible to link back to the output.
2. In Bitcoin the Hash function is used in the mining process to hash transaction data into an unique values by finding a nonce that generates a specific hash for each block.
3. Collision resistant refers to the unlikely probability (but not mathematically impossible) to get the same hash function output from two different inputs.

[Rick33]

each block has its own fingerprint(hash) converted by SHA256. this means its practically impossible to know the input, And its
2 the sha256 gives predictable cpu power input
they are used for mining
protection against hacking
3 it has to be resistant against hack attacks

[mac86tx]

1. Describe hash functions with your own words
   Hash functions can enable a 1-way (input --> output) generation of a unique digital hash output for each unique data input.

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).
   The Bitcoin has function has a difficulty adjustment every ~2-weeks after 2,016 blocks. Miners compete to solve the crypto-graphic hash.

3. What does it mean when we say that hash functions need to be collision resistant? (We didn’t use the term “collision resistant” in the lecture, but you will easily find this on Google, we add this question intentionally to make you research information on your own, that’s how you learn best).

A hash function is collision resistant if it is hard to find two inputs that hash a result of the same output.
It does not mean no collisions exists, but that they are hard to find.

[shane23]

1. A hash function is an input that always has a unique output or finger print.
2. hash functions are used in cryptocurrencies in the blockchain algorithm to create a unique output and to make it so coin is mined over a long period of time and not all at once.
3. The idea of collision resistant is that no to inputs would equal the same output.

[zookeeper]

1. Hash functions will convert an input into a hash string as defined by the Bitcoin hashing algorithm which is based on SHA-256. It’s low probability that the hash string is reversible due to the rigorous security of SHA-256 and can thus, act as a digital signature.

2. Hash functions are used to take specific attributes of a crypto, such as it’s transaction id, timestamp of creation/modification and convert them into a hash which can then be addressed on the blockchain. This is possible because the hashing algorithm was designed to be virtually irreversible in terms of reproducing the original inputs or crypto attributes.

3. This means that the hashing algorithm taking in the attributes of a crypto must generate a hash that is unique. A different set of attributes generating the same hash will cause a collision and this would be detrimental to the stability and security of the crypto currency.