Homework on Hash Functions - Questions

[Alko89]

@tojimmys

Miners are asked to create a hash from the proposed “block” that needs to be added to the chain. the challenge is to produce the “simplest??” 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? (I’m not getting this right yet I think lol).

Basically, but I would call it a digital fingerprint, signature is a different thing.

[The_Sambar_Vada]

1. Every unique input has a unique output
2. Bitcoin uses 8 H values and gives a 256 bit output, It runs the hash in 64 loops. The miners run the hashing algorithm on the message and anyone who gets the hashed output below a target value gets rewarded.
3. chances of finding 2 inputs having the same out put is extremely low and difficult, and it will take astronomical amount of time to find them.

[leewizza]

1. Hash functions are a one-way function that carries with it a unique digital fingerprint. It cannot be cracked and noone can work out what the input is, from the output only.

2. hash functions are used in mining for miners to prove they have done the work

3. that it’s impossible for there to be 2 colliding inputs

[JasonM]

1. Describe hash functions with your own words

There are many different types of hash functions, ultimately their purpose is to transform a unique input into a unique output.

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).

This is used in the proof-of-work consensus mechanism, the prior blocks will have its own unique output, so it is a way of validating that nothing in the previous block has changed, and then is used to allocate rewards to miners for validating the current 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).

This is the 2 unique inputs cannot result in the same output.

[Connor]

1. Hash functions are always one way functions and can convert an input into completely unique output. However outputs cannot be converted into inputs.

2. In the BTC protocol, hash functions are part of the block hashing algorithm, which is used to write new transactions onto the blockchain. Enables block mining speed to be consistent and adjustable based up on the supply of current computational output.

3. This relates to it being practically impossible for two inputs to produce the same outputs. This is important as it prevents transactions or information being faked by replacing with another input which produced the same output.

[Cryptek]

• Describe hash functions with your own words
  -> a hash function is a ‘program’ which will transfrom a ‘sentence A’ another ‘sentence B’ with a predefined length. For sentence A you have only one possible transfromation (setence B) and you can’t determine ‘sentence A’ if you know ‘sentence B’

• How are hash functions used in cryptocurrencies like bitcoin?
  -> each block, each transaction is calculated with the previous block. So if you change even even a little thing in the blockchain all the chain will be different.

• What does it mean when we say that hash functions need to be collision resistant?
  -> for one sentence A you have one sentence B. You can’t have a sentence C which could be transformed in sentence B. 1input -> 1 output / hash

[Hakim]

1. Its a unique input that produces an unique output, each output is a unique fingerprint and it can never go from output–>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.
   In bitcoin mining, the inputs for the function are all of the most recent, not-yet-confirmed transactions (along with some additional inputs relating to the timestamp and a reference to the previous block).

3. It needs to make sure that the inputs are completley unique?

[Iceman085x]

Hash functions are alpha-numeric equations that output a string of numbers and letters that act like a one way digital fingerprint for a specific piece of data. These functions are used in cryptocurrencies to link two blocks together by heading the current block of transactions to the previous block. These hashes need to be collision resistant so no two pieces of unique data have the same hash function.

[MarBlockchain]

1. Hash Functions are unique one way mathematical computation formulas, where each UNIQUE Input, gives a UNIQUE output, and it is not possible to deduce an Imput from an output.

2. Hash functions are used in btc for (1) tansaction data (2) Mining.

3. Collision Resistant. is a property of cryptographic hash functions, basically and in easy words “it is not possible to deduce an Imput from an output”

[Mako]

1. Hash functions take a unique input and to produce a fixed length output (e.g 256 bits long for SHA-256). This function has a special property in that the produced output is unique to that input. Any slight change would produce a totally different hash not even closely resembling the old one. The most important property is that, given the output, there is no way to derive the input used.

2. Hash functions are used as the basis for the POW concept, because if the block header if legitimate (because it is based on an earlier chained block), then it would cause the nonce (from the earlier block) to hash to the desired number less than a certain target number.
   So if the block is not legitimate because it is not based on earlier block, then it would not be possible to arrive at this number

3. Hash function need to be collision resistant so that we do not end up arriving at the same hash result based on two different inputs.

[Rocky]

1. Describe hash functions with your own words
   Hash functions encrypt data. They are are one way functions where each input produces an output or digital fingerprint.

2. How are hash functions used in cryptocurrencies like bitcoin?
   They are used to determine the accuracy of the information mined from block to block in the chain.

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

The input of the function must produce a unique result, and two different functions cannot produce the same result.

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. This means, that the input of the function must produce a unique result.

[Alko89]

@MarBlockchain

Collision Resistant. is a property of cryptographic hash functions, basically and in easy words “it is not possible to deduce an Imput from an output”

Collision resistance is the property of hash functions that give a low probability that two inputs would result in the same output.

[k_k]

1. Hash function is a function which transform inpt into output in unique way
2. They encrypt transaction data (private key?)
3. Collision resistance means that we will not get the same output or probability is low if we use many inputs

[Jmroach]

1. A unique digital fingerprint, each unique input will provide a unique output
2. Backbone of cryptocurrency security. Turns a random input of data and converts into a string of digital bytes. This prevents things such as double spending and makes the network immutable
3. When it is hard to find 2 inputs that hash to the same output. (highly unlikely but not technically mathematically impossible)

[Alko89]

@k_k

They encrypt transaction data (private key?)

Hash functions are not used in PK cryptography, for that the Elliptic curve function is used.

[Sam_Clare]

1. Hash functions are where putting in a unique input produces a unique output but can’t go visa versa. Altering the input creates a completely different output.

2. Part of the block hashing algorithm that Bitcoin uses to write transactions to the blockchain via the action of mining.

3. Collision resistance makes it impossible to have two matching inputs.

[ivory_elephant]

1. Hash functions take a given input of any length and convert it into a fixed output of a pre-determined length. In general they have 3 main qualities:
   a. they are deterministic (the same input gives the same output)
   b. they have a fixed output size (length of bits)
   c. they are uniform (the outputs are uniformly distributed)
   In addition cryptographic hashes have 3 qualities:
   d. they are one-way (the has output cannot be inverted to determine the input)
   e. they exhibit an “avalance effect” so that any small change in the input will trigger an avalanche that jumbles the output
   f. they are “collision resistant” meaning that there are no two inputs that will give the same output. (further details below)

2. Bitcoin uses a SHA256 hash function to show proof of work. Essentially, at the end of each block a number is added to give a unique output which must start with eighteen 0s. Finding the unique number which generates this hash on a block is the work of miners who compete to find the number first. An interesting property of bitcoin is that finding this number requires tremendous computational effort, but to have the number validated by the other nodes is trivial in terms of computing power.

3. A Collision, is what occurs when two unique inputs are fed into a hash function and generate the same output. Collision resistance of cryptographic hash functions means that the function has to be computationally difficult enough to make it practically difficult to produce a collision either through brute force or a birthday attack.

Sources for research:
https://nakamoto.com/hash-functions/
https://www.coindesk.com/bitcoin-hash-functions-explained

[Letsgoswimming]

1. A hash function is a one way, you cannot get input from the output.
2. Hash functions are used to write new transactions into the block chain.
3. Collision resistance means it’s super duper difficult to get two different inputs from the same output.

[bigbill]

1. Are one way functions which transform input text to unique output.
2. The miners pick some transactions up and using them as part of the input, they try to calculate a hash function to provide a new block to the chain.
3. Nobody should be able to find two different input values that result in the same hash output.

[c1cag1b3]

1. Hash function is mathematical process which gives each input an unique output. Process cannot be reversed.
2. They are part of the block hashing algorithm which is used to write new transactions into the blockchain through the mining process.
3. If a hash function was not collision resistant, we could find multiple messages which produce the same hash and sign resulting digest.