Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#5422

Describe hash functions with your own words

An hash function basically has an input and an output.
The output is a sort of “digital univoque fingerprint” of the input.
It is a unidirectional function, so it’s impossible to give back the input starting from the output.

How are hash functions used in cryptocurrencies like bitcoin?

Hash function are basically used to protect datas. Datas are mathematically, through an algorithm, converted into digital strings

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

When an hash functions is collision resistant means that is nearly impossible (low probability) to find two inputs that hash to the same output (A collision)

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#5423
  1. A digital fingerprint that helps prevent fraud.
  2. Keeps people from hacking or frauding the system
  3. When you try to keep from having multiple inputs that produce the same output or hash
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#5424

Homework on Hash Functions - Questions

1. Describe hash functions with your own words.
Hash function is a process in which input (any kind of data) is converted to a fixed length output. This process is irreversible.

  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 function is used to make the transaction secure in a blockchain. Bitcoin uses SHA 256 to get the hash of transaction data.

  2. 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 means no two inputs can have the same output. This makes the system secure.

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#5425
  1. Describe hash functions with your own words
    a function that takes a unique input and makes a unique output without any way of reversing engineering the output back to the input
  2. How are hash functions used in cryptocurrencies like bitcoin?
    They’re used for transaction data
  3. What does it mean when we say that hash functions need to be collision resistant?
    It means no two inputs should equal the same output
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#5426

1 digital fingerprint , you can check the authenticity of files or program’s

2 you can mine the sha-256 hashrate, generating a sha-256 hash with a value less than the current target solves a block and wins you some coins.

3 it should be hard to find things with the same hash

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#5427
  1. Hash functions are functions that are useful for checking data integrity. Every hash function needs to meet two requirements: 1. Each unique output corresponds to a unique input. 2. You cannot go back from output to input, that is, find an inverse of a hash function.
  2. Hash functions are used in cryptocurrencies mainly for generating public keys and block hashing.
  3. A hash function is collision resistant when given any two distinct inputs their hashes should not “collide”, i.e. be the same. Of course, this is not possible completely, but hash functions should be as much collision resistant as possible. This is achieved, for example, by making the hash value’s length bigger.
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#5428

1 A long and complex function that cannot be reversed.
2 Secures the new block, by making the miners use so much computational power, that it becomes hard for them to mine easily.
3 This means that a hash function must go 1 direction, and one only input===>output and not reverse.

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#5429

Hash functions are used to take input data and turn it into a unique “fingerprint”

Hash functions are used to pass transaction information anonymously.

Hash functions need to be collision resistant or an adversary can break the function easily.

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#5430
  1. Functions are a set that produces an output based on a particular input
  2. Hash functions are used in cryptocurrencies in order to create irreversible outputs of digital information.
  3. Hash functions need to be collision resistant in order to ensure the blockchain is tamper proof from obtaining the desired information from the hashed inputs
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#5431

  1. A Hash Function is a computer math that generates a unique random output, from a unique chosen input.

  2. Hash Functions are used to give and validate the blockchain transactions and they cannot be guessed.

  3. It means it is not possible to get two same output from one Hash Function.

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#5432

  1. Describe hash functions with your own words
    in a hash it is only possible to get from input to output and not the other way around. Makes a
    fingerprint

  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).

Block hashing is a core concept of Bitcoin mining. In this process, a block of unconfirmed transactions is fed to a hash function and a hash digest is generated. The miner uses this hash digest and adds some input from his/her end to generate an output that contains a certain amount of leading zeroes, currently the number of leading zeroes is 20. Generating these leading zeroes requires massive computational power and hence mining Bitcoin using the Proof-Of-Work mechanism is very costly and consumes large amounts of electricity.

  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).

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

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#5433
  1. Describe hash functions? In laymen terms, I would describe a hash function, simply as a function of mathematics that is used to map values arbitrarily and return a hash function with “hash values” , these values can then be index to a so called hash table and stored.
  2. How are hash functions used in cryptocurrencies like bitcoin?
    Cryptographic hash functions are used in cryptocurrencies to pass transaction information securely through the use of the SHA-256 cryptographic hash function algorithm.
  3. What does it mean when we say that hash functions need to be collision resistant?
    If a hash function is not collision-resistant then an adversary could break the function with little effort and in blockchain technology this would break the system, therefore, the SHA 256 is the cornerstone and foundation of this technology for its future and security.
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#5434
    1. A hash function is a function that produces a unique fingerprint of a fixed length, of the input given.
  2. In mining hash function verify the transaction
  3. Two inputs will not have the same result on the output
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#5435
  1. hash functions is a mathematical computation that converts into another blended value
  2. hash functions are used to pass transaction information anonymously
  3. hash functions need to be collision resistant to avoid being hacked. It means that is difficult to find any two messages that hash to the same value.
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#5436

  1. Describe hash functions with your own words. Unique input produces unique output, like a digital fingerprint.

  2. How are hash functions used in cryptocurrencies like bitcoin? A hash function is used to create a unique fingerprint of the transaction, which can be used to verify that the transaction has not been tampered with.

  3. What does it mean when we say that hash functions need to be collision resistant? It should be hard to find two different inputs that “collide” and produce the same hash.

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#5437
  1. Unique Input -> Unique output and it is one way unidirectional
  2. Hash functions are used to verify the transactions on the blockchain network
  3. No two inputs can result in the same output hash
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#5438
  1. To hash something means to scramble data and convert it to a numerical value. Each unique input produces a unique output. You can not go from output to input however.
  2. To encript data. For example BTC used SHA256 hash function. You can put a phrase in and it will “hash” the data to come up with a SHA256 output which is encrypted. You can’t go from output to input. This can be used in all kinds of examples on web servers, browsers, etc to encrypt data.
  3. Collision resistant means that it is designed to have an output that has a very high probability of being unique, with hardly any chance at all of having the same output as another phrase, the two inputs shall not collide (very high chance of not colliding, ie. being the same)
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#5439

  1. A hash function can create a unique string of alphanumerical values based on any data that will change drastically if it recognizes any changes in the original data set. Hash functions are a special type of function that have certain properties making it ideal for cryptography. The properties described in our reading that cryptographic hash functions contain were deterministic, the original data will always result in the same output hash, quick computation, it’s real fast, pre-image resistant, it’s infeasible to determine the inputt given the output, the hash changes completely with small changes in the input, it’s collision resistant, each input will have its own unique hash for the most part, and it’s puzzle friendly, it’s infeasible to determine the input hash (before concatenation) such that its result is equal or less than the difficulty level (in mining.)

  2. Hash functions are used to prevent new Bitcoin from being minted except through mining. This is because the data inputted in a hash cannot be altered or erased after enough on-chain confirmations, meaning the work required to secure that block cannot be copied, erased, or reversed. Hashing also keeps Bitcoin secure by encrypting transactions data through SHA-256. This data is kept secure by adding more data that has been hashed on top of it in a connected block. In order to compromise the data in the first block, you would need to first compromise the second, appended block. The difficulty to do this makes it highly infeasible after six or more blocks have been confirmed.

  3. We mean that two different inputs should not equal the same hash output. If this is the case, the inputs are presumed to be equal.

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#5440

  1. Describe hash functions with your own words
    A. The function is to produce a individual output specific to the input.

  2. How are hash functions used in cryptocurrencies like bitcoin?
    A. Producing a SHA-256 output by using part of the last transaction and the current transaction.

  3. What does it mean when we say that hash functions need to be collision resistant? A. Not accidentally producing the same answer from 2 different inputs.

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#5441

  1. Hash functions are a digital fingerprint where a input produces an output

  2. Bitcoin hash functions are results of a transaction on the blockchain.

    1. Each input is transformed to unique output and probability of two different inputs transforming to same output is infeasible if not impossible.
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