Homework on Hash Functions - Questions

[hannezzon]

1. From input, hash function computes a result that is a number with same number of digits regardless of the size of the input data. The input cannot be determined from the result.
2. Hash of transactions in a block are combined by further hashing in a Merkle tree. The final hash value of the block includes all transaction and hash from previous block. Which will be included in the subsequent block.
3. H(A) and H(B) will not be the same. (Infeasable, not impossible.)

[majstr]

1. Hash functions are a way of creating a unique “digital fingerprint” data represented by a set of numbers and/or letters.

2. Hash functions in cryptocurrencies are used to authenticate unique pieces of data.

3. Collision resistance in hashing functions means that there is very very little chance that a different input value would result in the same output hash. Which means that ideally every unique input should produce a totally unique output value so this way we can differentiate between every single piece of data based solely on it’s output value.

[Cryptotherapy]

A hash is a function that produces a unique digital output.

Hashing makes unique permanent bitcoin address/transaction using SHA256

Crypto hash H is collision-resistant when brute-force is negated due to irreversible and invariant outputs.

[CMP.crypto]

1. Hash functions is a unique input that gives a unique output, a digital fingerprint.
2. In one way Bitcoin uses hash function is to create new blocks via mining.
3. Each input will have its own unique hash

[sargold]

1. Hash functions give you a unique fingerprint output. When you give an input, the output is a unique fingerprint. If you insert a different input, you will get a totally different unique output.
2. bitcoin uses SHA256. The hashfunction is used for mining to add blocks to the blockchain.
3. It means that the output for an input can never be the same for a different input. The likelyhood of this happening is extremely small. So there can never be the same hash for different inputs.

[Piotr]

1. Hash functions creates unique digital fingerprint from the input.
2. Hash functions allows to check miners if they have the same data in block without comparing the whole data. They just comparing hashes and that gives the network security and speed of process.
3. It means that hash function cannot produce the same output from two or more different inputs.

[AlexParas]

Why everybody paniks with quantum computing and that it will break SHA256? It is not even possible and probably quantum computers will be a subject in 20-30 jears from now. Google just managed to make a quantum computing programm in prescale(actually they made a specific programm with a specific utility for a special perpose and this programm is just 100 times faster than normal) they don’t even get to quantum https://www.ibm.com/quantum-computing/learn/what-is-quantum-computing/ .
It is the same thing with AI. Many say Alexa or Siry are AI Systems but they are nothing else than AGI Systems. https://en.wikipedia.org/wiki/Artificial_general_intelligence

[Fabrice]

Yeah I know, but bitcoin wants to be quantum resistant for long time. You are right, today quantum computers don’t have enough qubits and is a pain in the ass to keep it cold and stable. But public keys gets hashed so you have that extra layer of security. if quantum computers becomes a treath in the future, ECDSA is more vulnerable than Sha256. So when you Transact and reveil your public key, never reuse that address.

[AlexParas]

To not reuse the address you have already once used, means you must have a wallet with multiple adresses or one that generates a new one everytime you make a transaction, correct? Is it like wallets that regenarate an adress every time you resieve a transaction?
I put it as questions because i think that it would be a good subject for the academy to put one-two videos with how in practise wallets work and what the difference realy is in every wallet type. For example this wallet has auto regenarators, or another one has one pin but not keys not you wallet. Another one is easier to use but another one is safer and so one. Because as a newbie in the academy but involved in the cryptospace one and a half year (also newbie) every wallet that i have tried out(and i have tried out over 10 because of curiosity mainly) is almost different and has it’s own way of work. So through the videos i thing everyone would better understand the functionallity and how really they work and would easier decide which he may preffer. ( just thoughts on something i haven’t found until now) @Fabrice @ivan @filip

[Dejan]

1. Hash functions are one way functions where each input produces an output or digital fingerprint.
2. Hash functions in Bitcoins are using in mining for new transactions on the blockchain. The inputs for the hash function are the unconfirmed transactions plus additional data related to time and the previous transaction. To solve the block miners try to combine all of the inputs along with data of their own so the outputs start with a bunch of 0’s. It takes a lot of computing power and guessing
3. Collision resistance means that is very difficult to find 2 inputs that produce the same output in a hash function. This is an important property in cryptographic hash functions.

[markfoster]

1. A hash function is an algorithm to get a unique digital fingerprint (hash) from an input and it is so complex that it is in feasible to be reversed.

2. They are used to store the transactions on the blockchain because they make it possible to store a larger amount of data like like an entire block plus the hash of the previous block and if one little part is changed it will know straight away because the entire hash of the block will change.

3. It means that no matter what input you enter it does not return the same output.

[Richie]

1. Hash functions are a unique finger print attached to a specific input.

2. Hash function is used to establish and confirm new blocks on the chain. This function completed by miners on the network. This creates a secure network.

3. Collision resistance - For the most part each input will have it’s own unique hash. No two inputs would ever have the same output.

[Maydad_Meiri]

1. Describe x as a certain string.
   h(x) is the hash function
   output comes in a fixed length for any length of x.
2. Cryptocurrencies are based on being built upon chain of blocks that contain two components the address of the previous block and the hash of the data inside the previous block
3. It means that there is an exteremly low possibilty (almost 0) to get same output to two different inputs

[4-Freedom]

1. They basically encode information by taking an input and creating a hash that is unique to that input.

2. They are used in mining and generating public addresses.

3. It means that it needs to be extremely rare that 2 different inputs would generate the same output.

[Littlejohn137]

1. A hash function is when through math a value of a specific length is created from a string of any length of text.
2. Hash functions in crypto are used to create unique numerical outputs of specific lengths and incapsulate the results of all the previous outputs into a unique number. Each resulting related and linked to the previous.
3. Hash function being Collison resistant means that it has a high probability no two inputs ever resulting in the same output. But no hash function is truly Collison resistant, it just would take a long time to do it.

[Ho11and]

1. When you give an input you get an digital fingerprint as the output which can not be reversed to find the original input data.
2. Hash functions are used to connect the blocks where the data is changed the hash of that block will also change and therefore make it invailid.
3. Collision resistant is where for each specific input there will be a specific digital output, so there is no way for any 2 inputs to ever produce the same output.

[Anton_Nortje]

1. A hash function takes an input string of any length and produces an output of fixed length.

2. Cryptocurrencies use hash pointers that point to a block of transactions and also contains a hash of those transactions. They are also used in merkle trees which makes it easy to verify if a transaction is present in a block.

3. It is infeasable to find two inputs that will produce the same output from the hash function.

[GidoForx]

@ivan

Homework on Hash Functions - Questions

1. Describe hash functions with your own words
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).
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).

1. A hash function is a piece of code which converts data into a bunch of random numbers and letters known as a hash. The hash can be used to verify that information in the blockchain is correct.

2. Really struggling to express the question

3. Collision resistance means that it will be impossible for 2 outputs to be the same.

[Fabrice]

it’s called HD wallets. ( Hierarchical Deterministic) Today most wallets work like this.

https://coinsutra.com/hd-wallets-deterministic-wallet/

[JasonB]

1. A hash function is a one-way function, in that you get a unique ‘fingerprint’ output number for every unique input value (number or string). SHA 256 being the most popular and one of the most secure cryptographic hash functions.

2. Hash functions are used in cryptocurrency protocols, like bitcoin’s, in order to facilitate proof of work and the difficulty level when mining, in a secure and protected way.

3. No two unique inputs should ever produce the same, or a shared, output. When considering the Birthday Paradox, the higher the amount of bits the hash function uses, the better.