Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#4199

Q1. Describe hash functions with your own Words?
A1. A hash function is a function that maps a character string of any length to a character string of a fixed length, its own hash value, better to say a digital fingerprint.
Q2.How are hash functions used in cryptocurrencies like bitcoin?
A2.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.
Q3.What does it mean when we say that hash functions need to be collision resistant?
A3. It meen that the network is very secure and the data on the blockchain can not be changed/hacked, if you give 2 different hash input then you should get 2 different hash outputs, something different is not secure.

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#4200
  1. Describe hash functions with your own words

a) Conversion of input to a unique predefined length hexadecimal number. Input (data) fingerprint.

  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).

a) Multiple miners verify transactions using the same hash functions. Malicious actors, trying to introduce bad data into the chain, will be identified by other miners who are unable to verify a transaction. That transaction will then be discarded.

  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).

a) A hash collision is a rare situation where two different inputs result in the same hash output. If this were to occur then a malicious actor would be able to swap the transactions with another user. To thwart this Bitcoin double hashes input by hashing the transaction and then hashing the output again.

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#4201

1. Describe hash functions with your own words

Hash functions are functions that produce a unique output for every input, meaning that two different inputs can never produce the same (hexadecimal) output. Another way to look at is that one would not be able to determine the input given the (hexadecimal) 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).

When a block consisting of many bitcoin transactions is verified by the network, the block of transactions is hashed i.e. a hex output is produced, and the block is added to the chain of previous blocks, with each block “pointing” to the hash of the next block in the chain. Thus, if a hacker were to try to change any transaction data in the block it would change the corresponding hash.

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).

It means that two different inputs will NOT produce the same (hex) hashed output.

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#4202

Hash function creates a fingerprint for any data could be a string such as “Hello World” or transaction data

They are used to secure the network by making sure there is no block that has been modified and using consensus to ensure that no data has been tampered with in the public blockchain.

Two different inputs will never have the same output.

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#4203

  1. Hash functions are unidirectional linear functions that produce an input and output.

  2. In Bitcoin, hashes are used to verify and add new transactions to the blockchain.

  3. Collision resistant means that there is a low probability of two inputs generating the same output hash.

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#4204

  1. Describe hash functions with your own words
    A hash function is a string of letters and numbers for specific given data or information. The input generates an 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).
    To identify digital signeture , validate transaction and produce new wallet addresses

  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 resistant means that it is highly unlikely that the same hash is created for two different inputs. Bitcoin achieves this by creating new blocks every 10 minutes, which reduces the chance of having a collision with high hash rate.

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#4205

Describe hash functions with your own words
Hash function is one-directional, from input to output (never output to input). Each individual input produces a unique fingerprint (digital signature) as the output. Any change to the input changes the output.

How are hash functions used in cryptocurrencies like bitcoin?
Hash functions are used in cryptocurrencies, like bitcoin, as part of a “block hashing algorithm” to write new transactions in the blockchain, through mining.

What does it mean when we say that hash functions need to be collision resistant?
Hash functions need to be collision resistant to prevent hacking. A collision environment allows hackers to use a digitally signed, authentic message, find the output of the hash function(digest), and substitute a fake digest for the real one, while using the same signature value to validate the transaction. For a hash function to be collision resistant it must be hard to find TWO INPUTS that hash to the SAME OUTPUT .

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#4206

Hello Marsrvr,

I love your one sentence answer - to the point.

#4207
  1. Hash functions work by taking an input no matter how big or small into the hash and getting a fixed 256bit output.
  2. A hash function in Bitcoin is used to hash transactions in each block. Since each transaction has a unique output the blockchain now becomes very secure.
  3. Collision resistant means not 2 different inputs cant have the same output.
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#4208
  1. Hash functions take any data input and assign that data an encrypted, digital fingerprint that is unique to that original data input.
    2: By their very name “crypto”, Bitcoin and other cryptos are assigned a cryptographically-secure digital fingerprint using SHA-256. Each crypto and verified-through-consensus transaction are added to a block via the mining process. If anyone tries to alter any of the data in any of these blocks, a new hash would be assigned to that chain… and, would not get verified and validated. Hash functions in Bitcoin help maintain data-integrity and security of the blockchain.
  2. Since a hash function takes ANY set of data of any size, and converts it to a fixed size, the possible input-set combinations far outnumber the possible output possibilities that can exist. Therefore, the reality is that some different inputs will be assigned the same hash value outputs… and this is called a “collision”. “Resistant” is not the same as impossible. While it is mathematically possible to find a collision, the computations required are astronomical… and would take too much time to find that it is of no real concern right now. Again, quantum computers could change all of that… and make finding these collisions easier. So, being collision-resistant is good enough to prevent anyone from finding the collision through a hack.
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#4209
  1. Hash functions takes data of any length as an input and transforms it into a limited combination of numbers and letters (how big the combination is depending on the hash program)
  2. Every block in blockchain has a hash code in which the data for the all the previous blocks is stored. This makes it impossible to modify any information on the blockchain since attempting to change the information of one hash code in the blockchain would be dismissed by all the other blocks.
  3. Collision in hash functions mean that two inputs create the same output in the sense that a ≠ b but h(a)=h(b). This can happen in hash functions occasionally but the probability of it is low. The lower the probability of it happening the stronger a hash program is
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#4210

  1. Hash functions are part of a hash algorithm that is basically used as a universal translator for computers. It can translate any form and size of data into an alphanumeric string of numbers. These algorithms exist of an input and an output.It’s a one way mechanism which gives a unique digital fingerprint of a unique input. The output of a function, the unique digital fingerprint is what we call a hash.

  2. These hash functions are what provide the revolutionary security on the blockchain. When looking at blocks on the bitcoin blockchain every hash points to the data in the previous block. So when someone tries to manipulate data on a block the hash on the next block is altered, because even the slightest alteration of the data will change the hash, which in its turn changes the hash of the next block and so on.

  3. It means that given two different inputs, for example input A and input B, it would be practically impossible or infeasable for them to have the same output, but not imossible. No hash function is collision free but when we are using the ASH-256 algorithm is is safe to assume that A is not equal to B or if H(A) = H(B) then A = B.

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#4211

Homework—Hash Functions

Functions, Hash Functions, Cryptography
  1. Describe hash functions with your own words

A hash function f(x) has a single input string e.g. file, text, transaction and produces a unique hash 256 bits long.

  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).

The hash function is used to produce a digest for the transaction data and also by miners to create and uniquely identify the block for a bitcoin reward. The unique hash calculated for the previous block is used when adding to the chain (i.e. add new block) so link the previous one.

  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 same unique output can not be produced by the hash function, bearing in mind it MUST have a single parameter as per pt 1 above, so that (f(a) = f(b)) is always false.

PS I hope this makes sense to you too!

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#4212

  1. Describe hash functions with your own words
    Hash functions create a unique output made of up numbers and letters that cannot be traced back to its input. This output functions like a fingerprint verifying the input

  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 cryptocurrencies as algorithms that need to be encrypted in order for transactions to be mined and added to the blocks

  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)
    It is virtually impossible for 2 different inputs to produce the same output

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#4213
  1. It´s a function that encrypts data and you can´t go back to the original data (input).
  2. They use it as a link between blocks to form the “block chain”.
  3. It needs to be difficult (almost impossible) that 2 inputs get the same output. That would break the chain I imagine.
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#4214
  1. Hash Functions are one way functions which transform input text to unique output.
  2. Hash functions are used to encrypt the transaction data so its secure and only the intended recipient can decrypt it.
  3. 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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#4215
  1. Describe hash functions with your own words
    • It’s an unidirectional complex function where 1 input generate another unique output except in extremely rare collision cases. The algorithm and the amount of possibilities and the complexity are so high that it’s almost impossible to get the original input with an 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).
    • For the generation of bitcoin addresses from a specific secret phrase or private key.
    • For the Bitcoin mining to reduce the size of the string header of a potential new block to add to the ledger. The algorithm is event used twice for the previous block hash. It’s also used to generate merkel root a kind of compressed digital fingerprint of the whole history of the blockchain.
    • Good article on the topic : https://www.mycryptopedia.com/sha-256-related-bitcoin/
  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).
    • When 2 different inputs will provide the same output due the algorithms imperfection and limitation of the possibilities.
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#4216
  1. Describe hash functions with your own words

Hash functions work such that for any unique input, a unique output or “hash” is produced. Even the slightest change will result in a completely unique result. But the same input will always produce the same output. The input cannot be derived from the output, meaning that the process cannot be reversed - it is strictly linear and “one-way”.

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

In cryptocurrencies such as Bitcoin, hash functions are used in a number of ways, including being used in the process of generating public and private key pairs. They are also used by miners to generate nonces, create blocks and link blocks together. Hashes are fundamental tools used in a variety of ways by blockchains.

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

“Collision” refers to the ability to produce the same hash output from different inputs. A hash function being “collision resistant” means that the probability of being able to generate the same hash output from different, unique inputs is extremely low.

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#4217

  1. Describe hash functions with your own words
    A hash function takes input and produces a unique output. In is a one way function, so it can never be reverse engineered, meaning that the input can never be deducted from the output. Also, hash functions will also produce the same output with the same input. The output produced is like a digital 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).
    In the crypto worldl, hash functions form part of the block hashing algorithm which is used to write new transactions into the blockchain through the mining process. It forms part of the proof of work process.

  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).
    It simply means that it is very hard to find two inputs that will have exactly the same output.

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#4218

  1. A hash function is a mathematical function that takes a set of characters (an input) and converts it to 256 bits (the output)

  2. Hash functions are used to write new transactions in the blockchain though mining.

  3. It means that it is incredibly difficult to find two inputs that produce the same hash output.

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