Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#2812
  1. Hash function are a unique language which encrypts regular information using complex algorithms.
  2. Hash functions are used to write secure new transactions in the blockchain during the cryptocurrencies mining process.
  3. When separate inputs produce the same hash output, that is a collision. ‘Collision resistant’ means makes sure the algorithm inputs create unique outputs.
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#2813

Describe hash functions with your own words:
A hash function is one that takes an input, then proceeds to ‘hash’ it. By ‘hashing’ I mean that it chops up the data which is processed to give a unique output. A hash function operates so that any input will receive a unique output and that similar inputs do not give similar outputs. It is near impossible to work backwards to find the input data from the output which is where the value lies in hash functions.

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 bitcoin as unique addresses are recorded as outputs from hash functions. That means that the information on the public ledger (blockchain) is recorded as hash functions and not by the users name. This allows for auditing to occur whilst keeping everyone’s private information off the blockchain.

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 refers to the scenario where two different inputs give the same hash function output. This would cause issues as transactions could be sent to an incorrect wallet etc. SHA-256 (bticoins hash function) has an almost infinite amount of possibilities and so the chances of the same output occurring from the function output are incredibly low, making it collision resistant.

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#2814
  1. Describe hash functions with your own words

Hash functions are one-way functions, that adhere to certain mathematical functions, with a variable input, get fixed output.

  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).

Cryptocurrencies, similar to Bitcoin, have hash functions as part of the block’s hashing algorithm which is used to write new transactions into the blockchain.

  1. 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).

The term Collision resistance is the property of a hash function that it is computationally infeasible to find two colliding inputs.

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#2815
  1. Unique one way coding that is almost impossible to break
  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. It means that every input have to have a unique output, there should never be same outputs for two different inputs - otherwise known as collision.
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#2816

  1. Hash functions are mathemathical computation to convert a data to some random characters of fixed length. Hash function always produce same output to same input and it is irreversible.

  2. Hash functions are used to hash content of a block and this hash of the block will be saved in next valid block. Incase if a hacker tampered some block, then the hash of each subsequent blocks will be affected thus enables the blockchain that there is some sort of tamper happened with the chain and they can discard that chain.

  3. Collisition in hashing means sometimes two distinct input produces same hash which can lead to a lot of problems. By adding salt and pepper and by adding more bits for hashing we can make hashing collition resistant.

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#2817

1. Describe hash functions with your own words
One way functions that cannot be reversed from output to input. A change of data will result into a completely different output. It is a digital signature.

2. How are hash functions used in cryptocurrencies like bitcoin?
Hash functions are used to write new or not yet confirmed transactions through the process of mining

3. What does it mean when we say that hash functions need to be collision resistant?
It is extremely hard to find two inputs that result into the same output therefor making it collision resistant

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#2818

  1. A hash function is a function that takes an input and gives a specific output for the input. If the input is altered, a different output will be given. The output is like a fingerprint for the 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 must be collision resistant because you don’t want the same output for 2 or more different inputs. If the output is the same for different inputs, it is called a colision.

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#2819
  1. Hash functions are functions where i transfer input to output and and every output have unique code. If i change only one latter in input output is totally different. That make hash functions unique.
  2. In Bitcoin we use Hash functions as minig algorithm for solvig math probloems. POW is very crucial for mining. All miners trying to find right answer for this math challenge. In Input we have some data just like timestamp, refferences tro previous block, moste recent transactions not yet solved.
  3. Most hash functions are not really collision resistant. But it basically means that you get the same output for two or more different inputs (which is also really, really hard to achieve).
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#2820
  1. Hash functions generate a unique hash from a unique set of data using algorithms.
  2. Hash functions are used to encrypt transactions
  3. Collision resistant means a hash should be truly unique so that no 2 sets of data produce the same hash.
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#2821

  1. a unique input produces a unique output, one direction only so that it can’t be hacked. This protects the information from being changed.

  2. SHA-256 function generates bitcoin hashes through various steps of mining.

  3. collision resistant hash function - when it is difficult to find 2 inputs that equal the same output.

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#2822
  1. A hash function is when a computer takes an imput and uses a mathmatical formula to producce an output of specific length.
  2. Hash functions are used in cryptocurrencies through mining, often where it is required to “double hash” in bitcoin protocall. i read that here if anyone is looking for a good article https://www.freecodecamp.org/news/how-bitcoin-mining-really-works-38563ec38c87/
  3. A collision is when 2 or more pieces of content produce the same hash and is most commonly done through " birthday attacks", using statistic information.
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#2823
  1. Create a unique fingerprint for every input. Input to output, but no output to input.
  2. Hash functions are used in mining.
  3. Collision resistance is preventing 2 different inputs from producing same output.
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#2824

  1. Hash functions take an input of any length and content and use a mathematical formula to produce a unique digital fingerprint of a specific length. Hash functions are one-way functions and it is infeasible to reconstruct the initial data from the hash when using secure hash algorithms with pre-image resistance (e.g. SHA-256, SHA-384).

  2. In the bitcoin protocol, hash functions are part of the block hashing algorithm which is used to write new transactions into the blocks. Bitcoin miners use the hashcash proof-of-work (PoW) algorithm and are expending efforts creating hashcash proofs of work which act as a vote in the blockchain evolution and validate the blockchain transaction log. The hashcash algorithm requires a large amount of effort to compute but proof can be easily verified. A bitcoin miner runs a computer program that hashes the transaction data with other data to form a block and earn a payment, but a block is accepted by the network only when a miner discovers by trial and error a nonce number that when included in the block yields a hash with a sufficient number of leading zero bits to meet the networks difficulty target. The hashcash algorithm requires the following parameters: a service string, a nonce and a counter. In Bitcoin, the service string is encoded in the blockheader data structure and includes: a version field, the hash of the previous block, the root hash of the merkle tree of all transactions in the block, the current time and the difficulty. Therefore the hash of each block contains the hash of the previous block which increases security. Bitcoin’s PoW uses two successive SHA-256 hashes and has a difficulty target which is reset periodically (every 2016 blocks, approximately every two weeks), this is to keep an approximate constant rate of block generation to one per 10 min. In bitcoin, the header of the block contains the merkle tree which depends on the included transactions. This includes the generation transaction to the recipient’s reward address, which in addition to providing the miners with the incentive to work, also ensures that every miner hashes a unique data set and acts as the randomization factor to avoid collisions.

  3. Collision is when two different inputs produce the same hash. In Bitcoin, this is highly unlikely but technically possible. Bitcoin uses SHA-256 which is a 256-bit hash, which has 2^256 possibilities so the likelihood of two pieces of content having the same hash is infinitesimally small. The “birthday paradox” states that to have a 50% chance of breaking the collision-resistance, you would need sqrt(2^256) which is approximately 3.4 x 10^38 attempts. Since miners are using the same previous block data and current transaction data, bitcoin uses the reward address as a miner-specific randomization factor to avoid increasing the chances of collisions.

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#2825

  1. A hash function is a mathematical function that converts a numerical input value into another compressed numerical value.

  2. In the bitcoin 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 is collision resistant if it is hard to find two inputs that hash to the same output.

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#2826
  1. Hash functions are one way inputs that produce a fixed length output.
  2. Bitcoin uses hashing algorithm to write new transactions in the bockchain during the mining process.
  3. Collision occurs when two different pieces of data produce the same hash
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#2827
  1. A hash function takes an input and use its algorithm will create a long piece of code to represent that input as a coded output.
  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. 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. This is what we mean when we say has functions need to be collision-resistant
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#2828

1.Describe hash functions with your own words
Hash function is a unique fingerprint, if someone wants to change something on the blockchain it would directly be seen by the nodes and not accepted because the hash would be totally different.

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).
Well, after searching on the web, I would guess that thanks to hash functions we are able to be certain of where the bitcoins are, knowing exactly in which wallet it is. Since the hash cannot be modified we are able to track it. (Thanks to correct me if i am completly wrong :slight_smile: )

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).
I think this means that even if 2 inputs seem similar it will never give the same output. that is why it is called collision resistant so that they can not ‘‘enter’’ in collision with the same hash. ( once more please correct me if what i am writting is completly incorrect )

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#2829

Hash functions are one-way functions that return a deterministic output of a specific length from an input, which can have any length.

For example, hash functions are used in the mining process of bitcoin that uses the Proof of Work consensus algorithm.
When transactions are submitted to the bitcoin network, they are collected into groups called blocks. Once a miner has successfully mined a block, it is added to the blockchain. For that, the miner has to find a hash with a certain number of zeros at the beginning. The input for the hash function has to include, among a few other things, the transactions of the new block and the hash of the last successfully mined block of the blockchain. To this the miner adds his own arbitrary piece of input data in hope of finding a valid hash for the new block.

A hash function is collision resistant when it’s hard to find multiple inputs resulting in the same output or hash.

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#2830

  1. Describe hash functions with your own words

    The hash function takes an input of any length and outputs a result of a fixed length

  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).

    Bitcoin uses hash functions, in its process to write the new transactions into the blockchain during mining, that become a permanent record of these transactions.

  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 is extremely unlikely for the hash function to give the same result to two differing inputs

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#2831

Hash functions ensure data to be immutable by linking blocks in a chain :wink:

Basically, but you must know that because the number of possible inputs (basically infinite) is always larger than the number of possible outputs (2^256) there is a possibility of collisions. Still due to the large number of outputs SHA256 provides it is highly unlikely a collision will ever occur. :slight_smile:

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