Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#4761
  1. Describe hash functions with your own words
    A Hash Function is a computation that for each unique Input gets you a consistent unique Output.
    This works a unique digital fingerprint: every time you run it on the same input it will result in the same output.
    In addition, they are one-way functions, since there is no way to go from the output to the input.
  2. How are hash functions used in cryptocurrencies like bitcoin?
    Hash functions are used in cryptocurrencies for several reasons.
    • -HF are an integral part of block creation: Blocks contain transactions that are represented with hashes contaning several pieces of data, such as the sender, the reciever, the amount sent. Blocks themselves are represented by a hash, which includes a list ot these transactions, the block’s number, a nonce value (number used once for mining the block), the previous block hash (which in turns lead to the blockchain formation), a timestamp and some more data.
    • HF securely allow transactions: Hashing allow users to get private keys to gain access to their own wallets, which is where their coins are stored. This is necessary for them to make transactions. In addition, hashing also lets user sign their transactions by deriving a public key from their private key, thereby authenticating them without giving away access to their coins.
    • HF provide pseudonimity: they work with public adresses derived from the user’s key, so the the transactions are publicly observable, but the user remains anonymous.
    • HF provide a data integrity test: since every little change in the input data results in a hugely different output, this way one can check if the original data in a block has been modified by comparing the original hash with the present one.
  3. What does it mean when we say that hash functions need to be collision resistant?.
    Collision resistant means that it is computationally infeasible to find two different inputs that hash to the same output. In practice this means that one can act as if any given input will produce a distinct hash, and in turn this results in more criptographical security for the hashing process.
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#4762

1.Hash function is a unique digital fingerprint for an input.
2. Hash functions are used in btc to create new digital fingerprints.
3.it is impossible to get the same output from 2 different inputs

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#4763

1 - Hash functions are one way functions where each input produces an output or digital fingerprint.

2 - Hash functions in Bitcoins are using for new transactions on the blockchain.

3 - Collision resistance means that is very difficult to find two inputs that produce the same output in a hash function.

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#4764
  • Hash functions are one way functions where each input produces an output or digital fingerprint.
  • 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.
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#4765

  1. One unique input will have one unique output. From the output, you can’t trace the input. It is only one directional.

  2. It is used as an added security for private and public keys. The hash function has converted the numbers into alphanumeric.

  3. There is a low probability of having two identical inputs that generate the same output.

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#4766

  1. A hash function is an unique digital fingerprint and is a one way function ie Input to output

  2. Hash functions are used in cryptocurrencies to pass transaction information anonymously

  3. Collision resistance means that each unique input will produce a unique output. It is hard to find two inputs that hash to the same output

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#4767
  1. Hash functions are a one way computation where the input of data is then turned into numbers and letters. The unique hash corresponds only to specific input. It is almost impossible to reverse the output.
  2. In crypto currencies each individual transaction on the block has an output of a unique hash made of numbers and letters. The hash pertains only to that transaction.
  3. Having more then one output for a single input could weaken the security of the data.
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#4768

  1. Describe hash functions with your own words
    This is a function that has an input and after the calculation in the function comes a specific output that does not allow to trace the input of the function.

  2. How are hash functions used in cryptocurrencies like bitcoin?
    For adding new blocks Bitcoin uses the consensus mechanism Proof of Work (PoW) also called mining. PoW means there is some computational work to be done in order to add a new block. The computational work in essence is finding a required output a hash function according to the amount of miners doing the computational work. The more miners, the more complicated is the required hash function output, the more hash function outputs a certain miners has to generate until the required output is generated. This computational work needs a certain hardware and therefore electricity to work. And due to the one directional nature of the SHA 256 it is currently practically impossible to hack the Bitcoin Blockchain. This feature of the Bitcoin as a cryptocurrency is one of the main characteristics why it is so successful.

  3. What does it mean when we say that hash functions need to be collision resistant?
    Shortly, it means that no one output of a function can have two similar inputs. The opposite means you could easily hack the input of the function and claim/dispute the output (your precious BTCs for example). That is why collision resistance is so important for the SHA 256 and the cryptocurrencies in general. Good detailed info could be found here https://cryptography.fandom.com/wiki/Collision_resistance

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#4769

  1. an input that gives a certain output that cannot go the other way around.

  2. has function is used in the process of mining, where it is used to solve problems in the algorithm.

  3. it means that it is hard with two different input gives a same output from a has function.

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#4770

  1. Describe hash functions with your own words
    Hash function are one-way functions with a unique input for a unique output that can not be reversed

    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).
      hash functions are used in cryptocurrencies like bitcoin - transactions produced as input on a hash function for a unique output.

  3. Collision resistant means every input has got its specific/unique output.

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#4771

  1. Hash function is a unidirectional, function which produces a unique binary output for each unique input of any datatype

  2. Since the output of a hash is unique, I can guess that bitcoin would use it for consensus of data, where if a certain hash function output of a data in the network is not equivalent to the other outputs of the same data, it is invalid.

  3. If a hash function is collision resistant, two unique inputs should not be able to produce the same output.

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#4772
  1. Describe hash functions with your own words

A one way computation that produces a unique output, where the output cannot be deduced to discover the input.

  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).

Bitcoin relies on SHA 256 to receive the input to generate the cryptographic hash output other data is also added to the header in the form of a nonce and can also include other data based on implementation to further alter the hash but without impacting the primary input. This process is part of the POW function in Bitcoin mining.

  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).

Methods of prevention use or develop a hashing algorithm to reduce the likelihood of the hashing algorithm to produce the same cryptographic hash when different ” x ” inputs are entered or assigned.

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#4773
  1. A hash function is a one way function, where each input produces fixed size output and from the output you never get back to the input.
  2. The hash function is the main method of generating blocks when the user mines cryptocurrency. It is necessary for integrating the block into the blockchain network. Also, the hash function is used for creating private and public keys.
  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.
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#4774

1. Describe hash functions with your own words.

Hash functions are a unidirectional way of turning any data input into a completely unique digitized 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).

Hash functions are vital to cryptos like Bitcoin as they are used to write new transactions to the blockchain via POW mining.

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 speaks to the hash functions’ ability not to take two distinct inputs that result in the same hashed output.

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#4775

  1. Its a kind of function wich allow us to produce one specific output by giving it one specific input. Its knowly that they’re one way functions. It means that you cannot take an output and reach the input wich produces it.

  2. Bitcoin, specifically, utilizes the SHA256 model to cryptographic its data. Like previously said, when you hash your data, you receive a alphanumeric string with 256bit of information. If you make a change, even a minimal like wiping a space, to any of your data, the string produced will be totally different. And if you modify even a single letter or number of this string, you cannot reach your data.

  3. It means that you cannot input two informations that produces the same output (hash).

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#4776
  1. Hash functions are one-way functions that transform a unique input into a unique output which can be thought of as representing a digital fingerprint of the input.
  2. The SHA-256 hash function is used for bitcoin-like cryptocurrencies. First it is applied to each incoming transaction record so that each one can be identified with its own unique, constant length (256 bits) digital representation - that is, its digital hash. After each transaction is verified by the miner, these transaction hashes will be accepted into the set of transactions forming the current block under construction. These block transaction hashes will be ordered by their timestamp and grouped into pairs starting with the first two entries. Each pair is then combined to form a new hash of that pair. The elements of this secondary set of hashes is then put through the same process, which in turn continues recursively forming shorter and shorter sets of hashes until the whole process reaches a single representative hash - called, the root hash. The graphical structure representing this recursive hashing is known as a Merkle Tree (after Ralph Merkle). This root hash is combined with the hash of the previous block plus a continuously guessed (by the miner) number called a nonce during mining to try to generate a hash result which is less than a target number. The target number is set by a separate algorithm to ensure that there is sufficient degree of difficulty (that is, Proof of Work) to maintain one new block confirmation about every 10 minutes. Variations in the target degree of difficulty is among other things affected by variations in the hashing power being utilized by the miners in the network at a given time.
  3. A hash function is considered “collision resistant” if it is hard to find two inputs that hash to the same output. (from Wikipedia).
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#4777

  1. Hash functions can be best discribed as a ‘‘unique translator’’ where the information (input) can be translated into a different language (output), but the output can’t be translated back to the input which makes the translation only available in one direction. input ------> output. Now there are different hash functions, like for example BTC which uses SHA-256.

  2. Hash functions is used in bitcoin for mining processes, it writes down new transactions into the blockchain.
    (please feel free to add things if im missing stuff in my explanation.)

  3. Collision resistance is that two different inputs won’t be ‘‘hashed’’ into the same output.

Ex. of a collision
Info ---------> abcdef01

Info’ ---------> abcdef01

different input same output

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#4778

  1. Hash functions are the formulaic output of various inputs.

  2. Hash outputs can be used as transactions in the blockchain once they have been verified by a consensus of nodes and/or miners.

  3. you don’t want distinctive outputs to be derived from more than an occasional rare input. If too many inputs result in the same output, the function will need additional work to vary outputs more effectively.

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#4779
  1. Hash functions create a fingerprint code to prevent hacking. They have only one way function, i.e. from input to output only. There is no output to input, otherwise it can be hacked and so is useless
  2. Hash functions are widely used in cryptocurrencies to pass transaction information anonymously.
  3. Hard to find two inputs that hash to the same output. The harder it is, the more secure it is.
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#4780

  1. Hash functions are functions where for each input you get a unique output (“digital fingerprint”)

  2. Hash functions are used in Bitcoin to verify financial transactions

  3. A collision resistant hash function is one where it is almost impossible to find two inputs that hash to the same output, which is important for the integrity of Bitcoin

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