Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#2391
  1. Hash function produces a unique digital code(digital fingerprint) for a given input.
    2.In Bitcoin the Hash function is used to hash transaction data. Also mining and finding a nonce requires finding a number that generates a specified hash in combination with data unique to that block.
    3.Collision resistant means two different blocks not getting the same hash.
1 Like
#2392

Describe hash functions with your own words

A hash function is an algorithm that accepts an input and gives out a unique output of specific length always. Small changes in the input yield large changes in the output. It is very difficult to ascertain the original input from the output; the more difficult this task, the better the hash function.

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).

Information about value ownership and transactions are stored in blocks on the blockchain in the form of hash output. The information to be stored is the input for the hash function; SHA256 in the case of bitcoin. The output from the hashing function is what is stored in 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 resistance means it is nearly impossible to have two different inputs yield the same output.

1 Like
#2393

  1. hash function is creating a unique output from any string of impute that represent a finger print of that transaction.

  2. Bitcoin uses SHA256 to create 256 bit of output no matter how short or how long the input might be

3

1 Like
#2394
  1. Describe hash functions with your own words. Hash function is data (input) that you hash to get a unique output of a particular length that can’t be reversed.
  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 function in bitcoin contains transaction data plus time and date and data on the previous confirmed transaction that’s then hashed for a unique fixed length output.
  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 two different inputs won’t ( after hashing ) generate the same output.
1 Like
#2395

  1. Private key = used to sign transactions to spend the funds
    Public Key to receive funds

  2. Two uses or cases of public key cartography
    encrypt plaintext and to verify a digital signature.

#2396

  1. Describe hash functions with your own words
    Any function that can be used to map arbitrary size data to fixed size codes

  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).
    Transactions are taken as input and run through a hashing algorithm . Bitcoin uses SHA 256 that gives an output of a fixed length

  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).
    -For security and prevent it from attackers

2 Likes
#2397

  1. a hash function is a unique fingerprint for a document. And if the document is even just 1 thing changed the whole fingerpring/hash is completely different.

  2. hash functions are used in bitcoin for transactions every transaction has their own fixed length of bits.

  3. that is very unlikely to have the same output as another output with the same input.

1 Like
#2398

1.A hashfunction takes any input and produces a fixed length output that is unique for every input that is not identical.
2.every block produced will be hashed together with the hash of the previous block.herefore alteration to the data creates a whole new chain that will be seen as invalid.
3.it means that it is highly unlikely(though not mathematical impossible)to get the same output from a different input through a hashfunction.

1 Like
#2399

This is the property of hash functions. Can you give a practical example where is it used in Bitcooin? :slight_smile:

Also you forgot to answer the last question :stuck_out_tongue:

#2400

SHA256 is the security, but collision resistance means that two inputs wont result in the same output. :slight_smile:

#2401

I think you made a typo here. It is unlikely to have the same output for another input. :slight_smile:

2 Likes
#2402

  1. A hash function is the process of taking data (or an input in this case) and giving a unique output that is unique to that specific input of a certain length via hashing it. Making it nigh-impossible to trace.

  2. They are used to encrypt and secure data as they are 1 way functions and there is no way to find the input through the output.

3.It means that it is very difficult to find to inputs with the same output. Because with hash functions even one change in the input will result in an entirely different hash.

1 Like
#2403

1 - Hashing is a way to generate a value from a text string using a mathematical function. Now the hash functions have their own properties, where each input has its unique output, the slightest change in the input will generate a totally different output. (like a fingerprint its unique and unrepeatable)
The second property is that you can only get the output from the input and not the other way around. It is a one way street.

2 -
Hash function in cryptocurrency mining: Blockchains, in which miners work, store information in Hash.
Transaction security: Each transaction is encrypted through Hash
Generation of public and private keys for cryptocurrency wallets

3- A collision occurs when different inputs produce exactly the same hash. Thus, a hash function is considered collision resistant until the moment someone encounters a collision.
Collisions will always exist for any hash function because the possible inputs are infinite, while the possible outputs are finite.
In other words, a hash function is resistant to collisions when the chance of finding a collision is so low that it would require millions of years of computations. So even though there is no collision free hashing function, some of them are strong enough to be considered tough (eg SHA-256).

1 Like
#2404
  1. Describe hash functions with your own words
  • They accept an input string of any length and give out an output of a fixed length.
  • Each unique input produces a unique output
  • The same output is generated for same input, no matter how often you run it through the hash function.
  • Any change in the input changes the output always.
  • To be useful they should be fast.
  • It is a one-way function. You can go from input to output but you can never go from output to input.
  • No two inputs should create the same output/hash.
  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’s proof of work (POW) algorithm is based on SHA-256.
  • All transactions are taken as input and run through the sha-256 hashing algorithm.
  • Miners perform this POW to try to successfully mine a block. A miner needs to hash the block’s header in such a way that it is less than or equal to the ‘target’. A nonce is introduced to make successful mining hard and hit and miss. Whoever figures out the correct hash first wins and gets a reward payed out in bitcoin.
  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).
  • No two inputs should create the same output/hash. No hash function is completely collision free but the probability of collision is so low that is statistically insignificant
1 Like
#2405

  1. A hash function is a “one-way” function which takes an input, text, or file, and creates a unique output of a fixed size. One-way means you can only go from input to output, you cannot go from output to 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. Collision resistance is a property of a secure hash function, and it means that two different inputs cannot create the same output.

1 Like
#2406

  1. Each unique input produces a unique output (a digital fingerprint). which can’t be reversed.

  2. Hash functions are used in cryptocurrencies like bitcoin to produce a unique digital fingerprint/signature to every transaction which is added in the block by the miners. To successfully solve a block miners combine all the inputs in such a way that the resulting hash starts with certain number of 0s.

  3. Collision resistant means two different inputs can never produce the same output.

1 Like
#2407
  1. Takes a string of numbers and letters, an input and turns into a 256 bit number, or unique output.
  2. Hash functions are used to encrypt data and ensure that any data changes are encrypted as well, such as unconfirmed transactions.
  3. Hash functions are collision resistant when it is hard to find two inputs that has to the same output. We want them to be collision resistant because than it is harder to break the hash code.
1 Like
#2408
  1. Hash function is irreversible function. You can not calculate input from output. Hash function also gives totally different output from slightly different input.
  2. Every block contains hash of previous block, so its impossible to change data in middle block.
  3. Because we need different output for different input. Same output for more different inputs would be vulnerability.
1 Like
#2409

  1. A hash function is a mathematical function that produces an output that cannot be solved in reverse to reveal the original input.

  2. Hash functions are used by Bitcoin to ensure that transaction data is completely secure. They are also used in Bitcoin mining to ensure that the addition of new blocks to the chain occur on a predictable and optimal schedule.

  3. Collision Resistance in the world of hash functions means that the function will not produce an identical output given a different input.

1 Like
#2410

Homework - Hash Functions

A hash function takes an input and produces a unique “fingerprint” that can be used to validate the original data.

Hash functions are used to produce signatures of transactions to be included in a new block and are a part of the overall “block hashing algorithm” used by miners to produce new blocks. Hashing functions are also used to confirm previous transactions and to derive wallet addresses from a public keys.

Collision resistance means that it should be hard for different inputs to result in the same hash output (fingerprint). If a hash function is not collision resistant an attacker could provide different input that resulted in the same hash (collision) thus tricking the network into believing the attacker’s input was valid.

1 Like