Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#4600

  1. A hash function involves a unique input and produces a unique output. However, unlike a normal function, an output from a has function cannot be reverted back to its original input. It can be described as a one-way function.

  2. Hash functions are part of the block hashing algorithm of the bitcoin protocol, which is used to write new transactions onto the blockchain via the mining process. The requirement for such a massive amount of computing power means that new bitcoins are mined over time rather than all at once.

  3. Hash functions are said to be collision resistant when there are more inputs than outputs, which inevitably have collisions; the more difficult they are to locate, the more cryptographically safe the hash function is. Collision resistance is commonly built into cryptographic hash routines.

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#4601

1- Hash function is a fingerprints provider, a mathematical function which with a unique input will result to a unique output. The transaction from input to output is on-way and irreversible. The output is called Hash.

2- In bitcoin mining, the inputs for the function are all of the most recent, not-yet-confirmed transactions (along with some additional inputs relating to the timestamp and a reference to the previous block). Changing a small part of the input for a hash function results in a completely different output. This property is crucial to the ‘proof of work’ algorithm involved in mining: to successfully ‘solve’ a block, miners try to combine all of the inputs with their own arbitrary piece of input data in such a way that the resulting hash starts with a certain number of zeroes.

While mining the miners needs to hash the block header in such a way that it is always equal or less than the ‘Target hash’ because only then they can add successfully add their mined block to the blockchain.

The target at the time writing should be an alphanumeric number which must have 18 or more zeros and should be less than the target value. And the target changes every 2016 blocks.

Miners arrive at this hash by applying SHA-256 hash function to block header, but this process is not so simple as it looks. To obtain the acceptable hash, miners need to play with the ‘nonce‘ in an incremental way.

Since this is a hit and miss exercise chances are very less that one might obtain the required hash (Target) with a particular number of leading zeros without making many attempts. And this Target is what is called a valid ‘Bitcoin Hash.’

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; that is, two inputs a and b such that H (a) = H (b). Every hash function with more inputs than outputs will necessarily have collisions.
If a hash function is not collision-resistant (there is no such thing as collision-free in hash functions because their output has a fixed length) then an adversary can break the function with little effort.

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#4602
  1. Algorithms that take an input and leave an encrypted output.
  2. String of letters taken in and then encrypted for security and able to be distributed efficiently.
    3.When two inputs produce the same output.
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#4603
  1. Hash functions are one way functions that result in digital fingerprints; and cannot be reversed to find the input. Every unique input results in a unique output.
  2. As said before Hash functions are used to encrypt transaction data into digital fingerprints/mining blocks. They will be will be used and decrypted by the recipient, in this case, the miner. This process results new blocks being added to the blockchain.
  3. Collision resistance is the difficulty to find 2 inputs that can be hashed and will result in the same output. You never want 2 inputs coming out with the same output.
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#4604

  1. Hash functions are a mathematical function that is only functional in one way and not reversible. Each input creates a unique output and an input can not be found using the output.

  2. Hash functions are used in bitcoin to create blocks and allows bitcoin to be mined over time. Using a hash function unique strings of numbers can be created using inputs.

  3. For a hash function to be collision resistant it needs to be extremely difficult or unlikely for multiple inputs to create the same output.

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#4605
  1. is a unique digital output for a given input (text,image).
  2. for BTC, the time of the transaction, and previous accounts are hashed to kept as data
  3. means uniqueness of each hash function
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#4606

  1. Hash is a mathematical function that converts an input of arbitrary length to an output of encrypted fixed length .

  2. Hash function are used in Cryptocurrencies as for transaction or mining .

  3. Collision Resistant is when it is difficult to find to input that hash to the same output.

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#4607

1. Describe hash functions with your own words

Hash functions are functions which give a unique output for each unique input. It is one-way, so you can’t reverse the output to find 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 part of the block hashing algorithm. This algorithm is used to write new transactions into the Blockchain. The input of the hash function are all of the most recent, not-yet-confirmed transactions(plus some additional inputs). Miners try to ‘‘solve’’ a block by finding a hash that starts with a certain amount of zeroes. This requires an enormous amount of computational power and locks in new transactions into a block, which is then added to the Blockchain.

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 hard to find two inputs that hash to the same output. It’s a property of cryptographic hash functions.

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#4608
  1. Describe hash functions with your own words

Hash functions are those which give a unique output for each input. There is no way of going from output to input (when that happens, the function is no longer useful, becomes obsolete and insecure).

  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 uses hash functions to store transactions into the blockchain. This process of storing transactions into the blockchain is called mining, and the algorithm involved in this is called ‘Proof of Work’

  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 resistant means that there is a very low to none possibility of getting the same output using two different inputs. When this is not fulfilled by a hash function, it is considered ‘broken’.

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#4609

Hash functions can go from input to output but can not go from output to input. The algorithm can be used with words or numbers of any size. Their like digital thumbprints

A hash is used for private keys to keep them secure and for mining. When it comes to mining hash is used to verify the transactions.

it means it is hard for two different inputs to produce the same output

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#4610
  1. Hash functions are unique inputs that create a unique output. Hash functions are represented in numbers and letters (0-9 & a-f). BitCoin uses Sha256 as its hash function. Hash inputs are one-way communication to the outputs and cannot be reversed. Once an input is made, a hash representation is created as an output. Any alteration to the original input produces a completely new hash output. This is for security purposes.
  2. Hash functions are used to recorded transactions on the blockchain. Instead of the user’s information being exposed for all to see on the blockchain, a harsh representation is generated instead. The user can remain anonymous, while the network is secured.
  3. Collision Resistance: is when 2 inputs do not end up as the same output.
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#4611
  1. Describe hash functions with your own words.

Hash functions are algorithms based on mathematical equations used to produce a unique output for each unique input in a linear way. These outputs are a fixed length and represent a unique fingerprint of the input given.

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

Hash functions are used to write new transactions in the blockchain through the mining process.

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

This means that two unique inputs need to produce two unique outputs.

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#4612
  1. Hash function is a secure and highly complex algorithm
  2. Bitcoin uses a universal cryptography translator that can take any data, number, letter, media file and translate it into an alphanumerical string.
  3. Collision resistance is the property of a hash function that makes it is impossible to calculate the mathematics of two colliding inputs.
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#4613
  1. Hash functions provide a unique output for every unique input however the reverse is not true. You can’t start with the unique output and figure out the input
  2. How are hash functions used in Bitcoin? Used to create new blockchains after the transactions are confirmed
  3. We say has functions are collision resistant if it is difficult for 2 inputs to have the same output
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#4614

Describe hash functions with your own words
A hash function is a one way conversion of data to a unique output that can be verified for integrity

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 bitcoin hash functions are used to verify the next block, with every transaction a piece of the hash is stored in the next block. Miners try to calculate the hashes together to confirm the integrity.

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).
Hash functions need to be constant with their results. This means that every ‘raw’ input of data must have the same output through the SHA-256 hash.

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#4615

  1. Functions work in a way where you put in information as an input and get an output. But with just functions, it is easy to figure out from the output what the input is. With hash functions, for example SHA-256 as bitcoin uses, it is near impossible to figure out from the output what the input was, meaning it is a one way function. The hash functions takes a input value and converts it to a compressed numerical value.

  2. Hash functions is used in cryptocurrencies when you mine a new block. You take the information/transaction into a hash function and get a numerical value that become that blocks hash value, or digital finger print if you may. When a new block is added to the chain they take to block before hash value and add the new blocks hash value which means that all the blocks all linked with the one before. This makes it impossible to change any information in any block, since all the blocks after it will become invalid.

  3. If a hash function is not collision resistant we could find multiple information that would produce the same hash which would make the hash unique. That means that a hash function is collision resistant if it is hard to find two inputs to the same output, making it extremely safe.

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#4616
  1. Hash functions are one way functions that create a unique hexadecimal output or ‘finger print.’
  2. Hash functions are used for block hashing in the blockchain (like Bitcoin) to write new transactions to the blockchain and verify accuracy.
  3. Collision resistance means that it’s incredibly difficult to find two inputs that hash to the same output.
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#4617

My Answers:

  1. A hash function keeps blockchain safe and secure. A unique inputs gives you a unique output, creating a fingerprint. It is a one way function meaning you can’t that an output and determine the input. It also ensures the integrity of the data.

  2. They are used to create new transactions onto the blockchain through the mining process and ensures the integrity on the data.

  3. Collision resistant means not being able to have two different inputs with the same output to that hash.

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#4618
  1. In hash functions we have a formula with an unique input based on wich we get as a result an unique output. If we change a single detail in the input we get a completly different output.
  2. The hash functions are used in the bitcoin blockchain for writing new transactions within the mining process.
  3. Collision resistance is the property of a hash function to be hard to have the inputs “a” and “b” being different and to have the same hash output.
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#4619

  1. Describe hash functions with your own words
    A hash function is a one-way function that processes an input of any size into a unique, fixed-sized output.

  2. How are hash functions used in cryptocurrencies like bitcoin?
    Hash functions are used in cryptocurrencies for security purposes to pass transaction information anonymously.

  3. What does it mean when we say that hash functions need to be collision resistant?
    A hash function has to be collision-resistant which ensures that it has to be impossible for 2 different inputs to produce the same output.

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