Homework on Hash Functions - Questions

[Xehlos]

1. With any given single unique input, accurate to even a space, comma or dot, will create an associated (256bit) output. With just the output, it is essentially impossible to source the initial input.

2. If I own some cryptocurrency, such as bitcoin, and I want to send it to my friend in Zambia, the transaction is executed securely through algorithms utilizing hash functions.

3. As long as any inputted data does not exactly mirror another (given time, location and associated task variables) there will not be an output which matches it. As more variables are added, such as in real life, there will not be one output which is identical to another. Hash functions themselves are not collision resistant, but once they are applied for an actual sound usage, they naturally become collision resistant.

[laughingbeach]

1- Describe hash functions with your own words.
A hash function is a one way function which generates a unique output for each input.

2)How are hash functions used in cryptocurrencies like bitcoin? .
Hash functions help to keep bitcoin secure by encrypting transaction data through SHA 256.
Hash functions prevent new bitcoin from being minted except through mining because the work needed to secure a block can not be copied or reversed.

3. What does it mean when we say that hash functions need to be collision resistant?
   being “collision resistant” means that no two inputs should ever generate the same output.

[ajuliab]

1. A hash function is a one-way function where each given input creates a unique output. The output can’t be reversed to its origin.

2. Hash functions are used in the mining process of bitcoin. Miners get rewarded for solving the hash for a bitcoin block, and the miners must try multiple combinations of inputs since a hash function is a one-way function. The first miner to find the hash target gets the reward.

3. Hash functions need to be collision resistant (meaning that two inputs can’t create the same output hash) in order to provide proof-of-work and create unique private keys.

[fullerideas]

1. Describe hash functions with your own words
   Hash Functions are mathematical functions that take a varied sized input which creates a unique fixed length output. Different/varied inputs cant create the same outputs and you cant take an output to work out an input.

2. How are hash functions used in cryptocurrencies like bitcoin?
   Hash functions on bitcoin are used in the block hashing algorithm. the hashcash PoW function is used in the writing of new transactions into the blocks via the mining process.

3. What does it mean when we say that hash functions need to be collision resistant?
   Collision resistant refers to a situation where two different inputs produce the same output. While not impossible but infeasible.

[IanC]

1. Describe hash functions with your own words
   A hash function is where an input to the function creates one output, but the output cannot be used to find the input
   The input can be any length but this will generate a fixed length output.
   So it is a 1 to 1, input to output, ie one fixed input stream will always generate the same fixed length output, but going the other way, the fixed length output will not generate the correct input.

2. How are hash functions used in cryptocurrencies like bitcoin?
   When a new block arrives, all the contents of the block are hashed, and this hashed value is then hashed again with the “nonce” string.
   If the resulting output is less than the dificulty level:
   The block will be added to the public ledger, the other miners notified, and work starts on the next block.
   If the resulting output is more than the dificulty level:
   The nonce string is changed and hashed again with the block hash.
   This will continue until either the resulting output is less than the dificulty level and the block is added to the blockchain,
   If 2 (or more) miners mine a block at the same time, the mined blocks are available for all the other miners, and they can choose one or the other.
   Then whoever mines the next block will decide which of the previous blocks is used, and the orphaned blocks are sent back to the mempool, except for any transactions that are in one of the accepted blocks.
   I learned something today

3. What does it mean when we say that hash functions need to be collision resistant?
   When a hash function is collision resistant it means the it is hard to find two inputs that hash to the same output
   ie. two inputs a and b where a != b but H(a) = H(b) is a collision.

[shah1]

1)Hash functions are one way conversions of unique inputs into unique outputs (digital fingerprint)
2) Hash functions are used to write new transactions into the blockchain through the mining process
3)collision resistant means if it is hard to find same output for two unique inputs

[Lauro_Cosby]

1. Hash functions is a way to give data string a digital fingerprint.

2. Hash functions are used in Bitcoin mining, known as proof of work. One example hash is used to encrypt transaction data.

3. It means that as a hash function here are no two inputs that will result in the same output.

[lolcat420]

1. Hash functions are a complex algorithm which is defined by each unique input resulting in a unique output and that you cannot ( should not) be able to reverse the output to find the input.
2. Hash functions are used to write new transactions to the blockchain. The inputs are the most recent, not yet confirmed transactions and in addition the timestamp and reference to the previous block.
3. Hash functions need to be collision resistant because it must be very rare or nearly mathematically impossible for two inputs to reach the same output.

[nachogama]

1. Hash functions generates an output from and input of characters in a way that there is not mathematical function to get back the input from the output

2. In Bitcoin hashes are used to encrypt the wallets private keys and to generate the new blocks of transactions/data during the mining process

3. A collision on a hash function occurs when given 2 different inputs you get the same output. In a collision resistant function it should be very hard to find 2 inputs that generates the same hash.

[r0bz078]

Describe hash functions with your own words

It Creates digital unique fingerprint to the input data of any size and produced a fixed size output data.

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).

Processing data entries input and convert into output.

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).

It doesn’t matter even if you give two nearly identical input it will still produce a different output. Even the slightest difference comma or space the output will not be the same.

[KyleO]

1. A hash function takes any data and converts it to SHA-256. This process is almost impossible to reverse

2. By creating addresses, private and public keys. Transforming transactions which can be recorded as hashes in a ledger

3. Collision resistant means it is statistically unlike to generate the same hash for a different input

[Vlad_Olareanu]

• 1. Describe hash functions with your own words
     -They are one-way functions in where a mathematical algorithm gives an output from calculating an input but it cannot be reversed.
• 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).
     -It is used for transactions, all transactions are taken through the algorithm as an input and converted as a hash output.
• 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).
     -2 different hash functions should not have the same output.

[Capt_caveman]

1. Describe hash functions with your own words
   a one way function that creates a unique output for every unique input and consistently produces the same value.
2. How are hash functions used in cryptocurrencies like bitcoin?
   work (as in proof of work for the miners
   public and private keys

What does it mean when we say that hash functions need to be collision resistant?
In computer science, a ‘hash collision’ is a situation that occurs when two distinct inputs into a hash function produce identical outputs. Resistent means that it is highly unlikely, but not impossible, for 2 outputs to match.

[Bhujanga]

1. Describe hash functions with your own words

Hash functions are used to encrypt data and give it a unique “digital fingerprint”. It takes the input data and sends it through complex mathematical operations to output a string of numbers and letters. The output is, as far as the hash has not been “hacked” yet, no more assignable to the initial input but, the output HASH can be used to check if a set of data has been manipulated, as only the slightest change in input data will output an entirely different HASH.

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 blockchain miners send input in form of new, still invalidated, transactions + timestamp + a reference to the previous block into the SHA256 until they can generate the desired output. While writing this answer, the current Bitcoin Block 453194, required the resulting HASH to start with a total of 18 zeros. To find this HASH takes indeed great computing power.

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 needs to be collision resistant in order to ensure, that there is no easy, or better no way at all, to find a second set of input data that will produce the same HASH as output. If it happens that two different inputs create the same HASH output, immediately the HASH function will be considered broken and unusable.

[JayJay]

1. Describe hash functions with your own words
   A hash function is a one-way function that uses an input string of any length to generate a unique output of a fixed length. This output is reproduceable using the same input and hash function but not reverse engineerable using the output and the hash function.

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 in multiple points within cryptocurrency processes. Two examples are:

• Entire blocks of transactions are hashed. The resulting hash is included in the block header.
• Bitcoin miners then combine the block hash with arbitrary numbers (the nonces) to try to get a block hash that is less than a predetermined value.

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 resistance means that it’s unlikely that two or more inputs will lead to the same output of the hashing function.

[Lee-Anna]

1. Hash functions has two unique characteristics. The first is that each unique input produces a unique output & the second is that the output data can never be converted to what the input data was - making it a one way function.

2. The hash function is used in cryptocurrencies like bitcoin as a method of security. With the block hashing algorithm used in Bitcoin to write new transactions into the blockchain through the mining process which uses Proof of Work, this allows the Bitcoin to be mined with combined processing power of all computers to solve a hash for a Bitcoin block.

3. In simple terms, collision resistant means that two different inputs do not produce the same output.

[Rezz]

Describe hash functions with your own words
Hash functions are mathematical formulas that take input data, apply a formula, and produce output data with its own unique digital fingerprint.

How are hash functions used in cryptocurrencies like bitcoin?
Hash functions are used to encrypt transactions in the form of blocks that miners add to the blockchain.

What does it mean when we say that hash functions need to be collision resistant?
To ensure that two inputs don’t have the same outputs.

[stevesirag]

1. Describe hash functions with your own words

A hash function is a one-way transformation of any data into a number. To be successful a hash function needs to be complex enough that it cannot be guessed, and therefore for the transformation to be reversed and the input revealed. This is an essential element in modern cryptography.

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

Hash functions are used in Bitcoin in that the algorithm that the miners are trying to solve is a hash function, in which the transaction data and random inputs are combined to find a hash with the prescribed target of consecutive zeros. The miner that finds it is awarded a bitcoin, and the block created with the transaction data embedded.

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

Collision resistance describes the value of the hashing algorithm in securing data. A ‘collision’ in this case is an example of 2 separate pieces of data resulting in the same hash. While this is possible with any hashing algorithm, the hash is ‘provably secure’ if the easiest way to solve it is by guessing the input through brute force.

[Nettie]

Hash functions are like putting bouncy balls in a playpen, mixing them up and then taking them out in the order you put them in…only with data. It is a one way function to secure the network.

Hash functions are used in cryptocurrencies like Bitcoin for security and safety.

Hash functions need to be collision resistant so that no two string of bytes will be the same.

[tonynapoli2]

1. A way of taking a string of input data and running it through a function to create a a output of data that is a fixed length

2. Hash functions are used in Bitcoin by providing a block hashing algorithm that records transactions to the blockchain. The inputs, which are pending transactions, are then taken and combined with extra inputs such as time of transaction, to try and find a hash that begins with many 0’s to “solve” and potentially receive Bitcoin. They also encrypt the transactions and provide a secure, immutable way of sending cryptocurrency.

3. Due to the nature of a hash producing a piece of data that is fixed length, and being that it can only output so many different strings of data, there can be a possibility of weaker hashes producing the same output from two or more different inputs. Being collision resistant prevents data from being manipulated or being fraudulent