Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#61

1
functions = calculations, input stands for an output
hash function = input is text and output is a string of numbers and letters

2
for identifying/creating addresses, signature, password verification, transaction date, etc…

3
if it is hard to find two inputs that hash to the same output; that is, two inputs

#62
  1. Describe hash functions with your own words

A function that no matter the input always produces an output of the same lenght.

  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).

Hashing is used in the mining proces where miners basically try to solve f(k|x) = y where k is the nounce and x is the hash.

  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).

That different inputs do not produce the same output (hash)

#63

1 hash encrypts data string into a given length of characters, sha256 would give you 256 hexadecimal characters
2 Hashing is used to create and verify the blocks of data in the blockchain and to encrypt your private key
3 this means the chance of an output having more than 1 input is very low, so low that if output for h(A) is the same as h(B) then A=B

#64

The hash function is a way of hashing the input into a unique digital fingerprint.

Hash functions used in mining blocks and eventually verifying new transactions.

That every output shold be unique.

#65
  1. Hash functions are a method of taking input and through math processes create a fixed length string that the exact same input will always produce the exact same output. Hashes used for cryptos must also not be able to go in reverse.
  2. The hashes are use to create the blocks by combining prior hash results, transactions and other data into a single hash. The large number of possibilities make sure that each result is immutable.
  3. Collision resistant is how likely different inputs could give the same output. H(a) is not equal to H(b) but both = c. So to be resistant you would need a large enough minimum input so that collision will not occur on the outputs.
#66

Describe hash functions with your own words:

Hashfunction is a one way function. you can only go from input to output.

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).:

SHA 256 is the bitcoin hash function used for transactions.

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 (allmost) impossible to get the same output from a hash function… without knowing the input

#67

Homework on Hash Functions - Questions

  1. Describe hash functions with your own words
    -Function takes input for calculations and outputs the result.
    -Hash functions gives you unique output for your unique input. Basically if you want to secure your information you can use hash functions to do so.

  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 to write new transactions into 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).
    -There is more inputs than outputs for any hash functions so finding out two same inputs for same output is possible. Because it is really hard to find those two matching inputs with the same output it is collision resistant

#68

Hash functions are a unique input which gives a unique fingerprint.

A cryptographic hash function is a special class of hash functions which has various properties making it ideal for cryptocurrency like bitcoin.

If you are using SHA-256, it is safe to say that it will take a long time to find a collision. Because each input will always have a unique output.

#69
  1. input can be different length, output stays fixed length. Can go from input to output, but not from output to input.
  2. hashes from previous blockheader is used in new block on blockchain. That makes the pointerchain.
  3. infeasibility that two different strings generate the same hash.
#70

Hash functions are always a one way function that takes and input and produces a unique output
a finger print.

Transactions are run thru hash functions SHA 256 to provide an fixed output for security

Having two inputs Hash to the same output is not workable. this is colliding. Same inputs should not
produce the same output.

#71

Describe hash functions with your own words

  • Hash functions are special functions that produce a unique output for each unique input by running the input through a complex hashing algorithm.

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 SHA-256 to hash transactions and also for incentivising miners who compete in mining new blocks.

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).

  • As hash functions are designed to produce unique outputs, a collision would practically break the function and render it useless as it would allow for the production of identical outputs for different inputs. Although no functiona is 100% collision resistant, the odds for SHA-256 to produce a collision are so small that they are not even taken into consideration.
#72

  1. hash function is a function that will give you the digital signature, with a fixed output length and not possible to look for the original input given the output.

  2. it is used as a digital signature for each of the block of bitcoin transactions. Not only it use the current block to produce the signature but also has the input of the previous block so that there is a linkage of new block with the older blocks.

  3. So that given different inputs, it will not be possible (or negligible probability) to produce the same output.

#73

  1. Hash functions are a method of data encryption that produces a fixed length deterministic, collision resistant output whatever the input.

  2. Hash functions are used in cryptocurrencies to link blocks of encypted data together. In BTC, each block contains a hashed key to the previous block and a hash encrypted output key to send to the following block.

  3. Collision resistant means that no two inputs will result in the same output. No hash function is collision free, but the time scale involved to find them means it is irrelevant.

#74

  1. Describe hash functions with your own words.
    They are a one way function that goes from Input to Output. If a method is discovered that allows to go from Output to Input, then the hash is not cryptographically secure (i.e. MD5).

  2. How are has functions used in cryptocurrencies like bitcoin?
    They are used to hash together each block. If the data is manipulated it changes the hash and therefore breaks the chain history.

  3. What does it mean when we say that hash functions need to be collision resistant?
    This means that it is hard to find two inputs that hash to the same output.

#75

  1. Hash functions are a unique set of numbers that give a specific output.

  2. With bitcoin, hashes are used to add new transactional data to the blockchain.

  3. Collision resistant means that no 2 inputs can hash to the same output.

#76
  1. Hash functions are the fixed unique out you get for every input you make. If there is a change of input by even a tiny space or dot, the output which is the hash function will be different. It is a one way traffic function that does not go from output to input. It only goes from input to output.
  2. How hash functions are used in cryptocurrencies like bitcoin is simple…It takes the transactions (input) of any length and run it through an algorithm SHA256 and produce an output of a fixed length.
  3. Collision resistance is a property of cryptography. A hash function is collision resistant if it is hard to find two inputs that hash to the same output. Example could be tow inputs a and b. H(a) = H(b), but a ≠b
#77
  1. Hash functions in one direction only that is output. You can not go backwards to discover the input. Has 256 uses 0-9 and A to F with 64 total in the Hash that was created. You can create hash with input of any digital asset.
  2. It can be used to confirm a transaction and mining.
  3. It means two inputs create the same output that can be exploited if discovered.
#78

1. Describe hash functions with your own words
Hash functions create a unique output (of fixed length) for a given input.
2. How are hash functions used in cryptocurrencies like bitcoin?
The transactions go through the SHA-256 hashing algorithm creating a unique hash for them.
3. What does it mean when we say that hash functions need to be collision resistant?
It means that two different inputs cannot have the same output.

#79

Hash Functions

1 Hash function is a computation of an Input to produce an Output

2 In bitcoin the hash functions are sent using digital signature.
It is the same as sending an encrypted message via public key but since the blockchain is trustless
and also semi private the blockchain requires the digital signature to verify that you have bitcoin

3 Collision resistant is the probability of two different inputs resulting in the same hash

#80

  1. Describe hash functions with your own words
    A hash function will take any unique input and return a corresponding unique output of fixed length that acts like a digital fingerprint. It is a one-way function which means that you cannot derive the input value from the output value.

  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).
    Bitcoin uses a block hashing algorithm when writing new transactions to the blockchain. This process is known as mining and is responsible for verifying each bitcoin transaction. The input consists of header data, including timestamp and previous block reference, along with a list of the most recent unconfirmed bitcoin transactions.

  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)
    Hash functions need to be collision resistant to ensure that no two input values will result in the same output.