Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#641

1.the hash function is all the details of a transaction converted to a nearly unbreakable code.

  1. the hash links all transactions creating immutability.

  2. it means that it isnt easy for 2 inputs to find the same output

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#642
  1. A hash function is to convert any data into a digital fingerprint. The slightest change in the data will change the hash result.
  2. Cryptocurrencies uses the hash function to generate keys and address and also in mining for new transactions.
  3. The function needs to be collision resistance means two different inputs cannot have the same hash output.
#643
  1. A function that takes a unique input and produces a unique output with a specific length
  2. It takes part of a previous transaction to generate part of the next block
  3. The output of a hash function shouldn’t occur for different inputs. They should be unique
#644

Hash functions are functions that have been hashed to a certain value size and cannot be reversed to find the input. Hash functions need to be collision resistant so that no inputs hash’s out to the same output.

#645

  1. Hash is a program that gives a number to any transaction. This number cannot be changed

  2. a transaction comes in as input and after hashing comes out as output that cant be changed.

3 Collision resistance is a measure of difficulty which you can hash different outputs to the same input with

#646

  1. Describe hash functions with your own words

    A hash function uses a unique input to give a 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).

    The hash function is used as an added protection for the users public key.

  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).

    A hash function that is collision resistant simply means there can’t be more than one input producing a the same output.

#647
  1. Each unique input gives a unique output
  2. In the abstract, a hash function is a mathematical process that takes input data of any size, performs an operation on it, and returns output data of a fixed size.
  3. Every hash function with more inputs than outputs will necessarily have collisions. Consider a hash function such as [SHA-256] that produces 256 bits of output from a large input.
#648
  1. Hash functions are unique in their input and produce a unique output. They are so to speak like a human fingerprint [every finger is unique in the society and there is no second equal finger to be found on this planet].
    2.Hashing is generating a value by using a mathematical function and is one way to implement and create security during the process of adding on a new block in a block chain. The mathematical formula which creates the hash, helps to uphold the security of the transmission against tampering.
    3.Its the uniqueness that makes the mathematical function of the hash collision resistant because no hash is the same.
#649

  1. A hash function is a one way computation in which you can go from an input to a unique output or digital fingerprint and not vice versa.

  2. In bitcoin, hash functions are used to write new transactions into the blockchain through the mining process. In bitcoin mining, the inputs for the function are all of the most recent, not-yet-confirmed transactions and the output will eventually be a block once confirmed, that contains.

  3. Given two different inputs A and B where H(A) and H(B) are their respective hashes, it is infeasible for H(A) to be equal to H(B).

#650

  1. Hash function when you generate an output depending on numbers or strings in the input. It is processed by running it through a hash algorithm.

  2. In bitcoin you use Secure Hashing Algorithm (SHA-256) which always use 256 bits of length (hence the name). It works as a one-way function so the data can’t be generated from the hash.
    It is used in mining as proof-of-work and in creation of bitcoin addresses to improve security and prevent hacks.

  3. It is a property of cryptographic hash functions and means that it prevents two different inputs to generate the same output. Each unique input needs to give a unique output.
    It is important because otherwise a hacker might be able to manipulate the ouput by finding the same message and replace it with the one generated in the hash functions, which destroys the digital signature.

#651
  1. each unique input creates a unique output.
    From the output is ( almost impossible to discover the input)
    2)Because no matter how long is the input data the output will be always the same length SHA-256
  2. Using Hash SHA-256
    Input the same data , you always get the same output.
    So it is collision resistant as you cant input different data and get the same output/
#652
  1. Hash functions are a tool to convert any digital data to a unique finger print (a unique number associate with the input). In order to a called a hash function it should satisfy the following:
  • Uniqueness: must produce a unique and same result with same input every time.
  • One-way conversion: can be easily and quickly convert an input to output but must not be done reversely.
  • Collision resistant: the chance of 2 inputs produce the same output is astronomically low that it’s negligible to the security of the network.

In case of Bitcoin Network SHA256 is used which give the answer in form of hexadecimal number.

  1. Hash functions can be used to sign transaction by the owner and the unique finger print is broadcast to the network as proof of ownership. The transaction can easily be verified but impossible to trace the private key of the owner.

  2. Collision resistant: the chance of 2 inputs produce the same output is astronomically low that it’s negligible to the security of the network.

#653
  1. Describe hash functions with your own words
    A hash function take an input and produces a unique output that is consistently the same. It is hard to impossible to use the output to produce 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).
    The transaction data is hashed. A block in the chain contains a hash of the previous block in the chain’s data.
  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 is should be very unlikely that 2 different inputs produces the same output.
#654

  1. hash functions are functions were unique input produces uniqe output and were its not possible to go from output to the input! hash functions convert data into uniqe number of 64 bits! its one way functions!

  2. cryptocurrencies are using hash functions to secure the process of message / data transmisson.a hash wil be created through a formula which protects the security of transmissions!

  3. collitian resistant means that two different inputs cannot have the same output . input A and B is hashed into H (A) and H(B) . H(A) and H(B) can never be the same!

#655

  1. A hash function is a mathematical calculation that generates an outcome that does not allow you to recalculate the original input. Although it is theoretically possible, it is highly unlikely it will be done.

  2. Mining machines calculate hashes via inputs from previously created blocks

  3. Its means that from the outcome of the hash it is mathematically highly unlikely to recalculate the original input.

#656

  1. A Hash function is a bit of code/data that has a given instruction or message that is protected by a unique finger print and can not be cracked.

  2. Each block is hashed and if a hacker tries to change the input of a block from 2 BTC to 10 BTC for example all other hashes will be changed because they are all connected thus isolating that particular block.

  3. Each Hash has its own unique input.

#657

  1. A hash function is a function that takes some input of variable length and produces some fixed-length output.

  2. One way hash functions are used in bitcoin is to produce hash pointers, tying the blocks in the chain to one another, and the transactions in those blocks to one another.

  3. Collision resistance means that for all practical purposes, it is impossible for any 2 unique inputs to produce the same output. In reality, this is impossible, because the set of all possible inputs is larger than the set of possible outputs. But for hash functions like SHA-256 there have never been any collisions found.

#658
  1. A hash function outputs a unique fixed-sized value for each input.
  2. Hash functions are used in bitcoin to share a message, most commonly a transaction between certain participants. It is visible to everyone, however cannot be made sense of by any other outside the intended parties.
  3. Collision resistance refers to the unlikelihood that two different inputs can produce the same output. In order for a has function to work, it needs to be as close to impossible for this to happen.
#659

  1. Hash functions are operations where there is an input and a coded output. It is deterministic, which means for every input there is always a matching output. A change in the input will completely change the output. It also has a quick time to compute. Lastly, it can only be reversed by brute force, but that will take a very long time to achieve and costly to do, making it infeasible.

  2. Hash functions are used in cryptocurrencies to save transaction information within the blocks.

  3. When we say that hash functions need to be collision resistant, it means that each input will have to produce one and only one output.

#660
  1. Describe hash functions with your own words

Hash functions is generating an output with a fixed-length from any input.

  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).

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.

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).

  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).

Hash functions create an output has a fixed length (deterministic), so we want to avoid create to same output twice.