Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#1043
  1. it take an input and gives an output but you can’t figure out the input from the output
  2. there used to write new transactions into the blockchain through the mining process
  3. you can’t have the same output from the input of the hash
#1044

  1. Hash functions are special functions that give a unique output to each unique input. with a hash function it is not possible to calculate the input based on the output.

  2. in BItcoin, the transaction is taken as the input. the hashing algoritme then gives a fixed length output

  3. It means that each input will have it’s own unique hash

#1045
  1. Describe hash functions with your own words

Functions that are one way. They provide a unique output for every unique 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).

Hash functions are used in the bitcoin mining process which rewards miners for solving the block via complex computations

  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).

If it is hard to find two inputs that hash to the same output then we say that a hash function is collision resistant

#1046
  1. Hash functions are used to generate a fixed length (bit) of data for any amount of input data. Meaning, however large or small the input data is, the hash function will fix it to the required length encryption.
  2. The SHA - 256 hash function is used in Bitcoin to reduce any amount of input data value to a 256 bit code. It is infeasible to determine the input value from the output (hashed data). This makes Bitcoin highly secure, immutable. Because of this, the user can add data to Bitcoin, but cannot change or reverse previous hashing.
  3. Hash functions need to be collision free meaning the hash function should not generate the same hash output for two or more different input values. For every different input value, there is a different output value.
#1047

  1. A function that gives you an unique output and you can’t determine the input from the output

  2. hash functions are used to pass transaction information anonymously

  3. It’s nearly impossible for two different inputs obtain the same output

#1048
  1. Describe hash functions with your own words

Hash functions are a specific class of functions with some precise features that take an input of any size and convert it into an output of a set size, in a way that it is not allowing to deduce the input from the output.

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

On the Bitcoin blockchain hash functions are used to create anonymous, immutable transactions, benefitting of the non feasability of revert engineering the input starting from the output, in a one way sense. Also the hash functions of previous and next blocks are included in any given block to link them.
A hash function should always be giving the same output, given the same input. They can be used for several purposes.

  1. What does it mean when we say that hash functions need to be collision resistant?
    The concept of collision resistance stands for the impossibility to have to different input giving the same digest (output) using the same hash function.
#1049

Math formula with large input and large out put 16 base. Energy used to come up with math finger print smaller than answer for conformation for block. Two different numbers should’t produce same results

#1050

A cryptographic function that accepts an input and produces an output or digital fingerprint.

During the mining and validating processes, the Bitcoin code will use the SHA-256 hashing function to validate transactions on the blockchain. This involves guessing various inputs for the SHA-256 function. Once an output of a given input starts with a certain number of 0s, we have a match. This uses a lot of energy to find these matches. This is the Proof of Work.

Collision Resistant means getting the same output from a hashing function that has different inputs.

#1051
  1. Describe hash functions with your own words
    Two main principles, firstly each input produces a unique digital output (fingerprint) and secondly you can not deduce the input from the 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).
    They are used in mining to try and mine a block. The calculation is done many times to compare with the difficulty level. The hash string contains nonce values that are random values added to the end of a hash. If this recompiled hash is less than the difficulty level. If it is the block is accepted into the blockchain, if not the hash is done again
  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).
    As each hash is totally unique there should be no way that 2 inputs can have the same hash value (output).
#1053
  1. A hash function is a function that produces a unique digital fingerprint as an out-put of a unique in-put of a data set or file.
  2. They are used to encrypt transactional data in order to prevent unwanted changes to the data. They are also used in mining in which the newly confirmed block of transactions is supposed to match with the nonce in the header of the previous block.
  3. Hash functions are collision resistance in the sense that it is practically impossible to produce the same output for different input data.
#1054
  1. A Hash function is a one way mathematical function that produces a unique output from a unique input . This output from a hash function is of a constant fixed length no matter the length or size of the input value.
    In other words the traversal route for a hash function can be described diagramatically as:

input ----> Output and not Output -----> Input

  1. Hash functions are used to hash the transaction data in Bitcoin (to preserve integrity) and also in the overall Bitcoin Mining process.

  2. Hash Functions being collision resistant implies that there are no two hash functions that are the same.

#1055

Homework on Hash Functions – Questions

  1. A hash function is a way of generating an output, in the form of a fixed length string of numbers and few letters, from an input of any lenght. The slightest change to an input will result in a completely different output. Hash functions try to make it impossible to guess the input by knowing the output.

  2. Hash functions in Bitcoin are used to write new transactions into the blockchain via the mining process. The input of the hash functions are the unconfirmed transactions, timestamp related input and a reference to the previous block.

  3. This means that there is alsmost no possibility for duplicate inputs to lead to the same output. If this would be the case it would be far easier to brute force the system.

#1056

  1. Describe hash functions with your own words
    Hash functions are such, that each unique input produces a unique output. You can go from input to output, but you can never go from output to 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).
    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).

  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 it should be very hard to find two inputs that hash to the same output for the hash function to be collision resistant. Every hash function with more inputs than outputs will necessarily have collisions.

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#1057

  1. A hash function Is a function that takes an input and produces a unique output. This output is only possible to get with the exact input used, it is like a digital fingerprint.

  2. In cryptocurrencies like Bitcoin the hash function is used to make sure all transactions being secure to changes. It is used in the mining process where the miners guess their way to the next block using SHA256, a hash function.

  3. To say that a hash function is collision resistant is meaning that the possibility of two hash functions producing the same output out of different input is virtually impossible.

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#1058
  1. Hash functions are functions of witch the inverse function is unknown and may be never discovered.

2.It’s used to create addresses, private and public keys. Blocks are linked together, by turning each block into a hash witch is then stored in the next block.

3.It is very unlikely for two different inputs to get the same output.

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#1059

  1. Hash function makes from any string of data a hash (which is a fixed lenght sequence of numbers and letters). Important thing is that the same input always make the same output hash.

  2. Hashing functions of bitcoin are a part of a block hashing algorythm. Inputs for hashing are not yet confirmed transactions and the output must a be a hash which starts with 18 zeros. Each transaction also has its own hash.

  3. Collision resistant means it can avoid finding more different inputs for the same output hash.

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#1060
  1. Hash functions are useful in digital security applications because they take a input value of arbitrary length and produce a hash value of fixed length. This is useful because it is difficult for somebody to find out the original input if they only have the hash value. A good example of this in action is when you use a password to login to an application.

2.Hash functions are used in bitcoin for adding information to the blockchain. Miners use a lot of computational power to turn input data such transaction information and timestamp into a hash with 18 zeros which will then solve a block.

  1. Hash functions need to be collision resistant means that if I have two random inputs, what are the chances that it will produce the same output. Hash functions being collision resistant means that this is extremely unlikely to happen but still possible.
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#1061

  1. A hash function is a formula, that can be used not only on numbers but also on text or other types of data. It is used to create a “fingerprint” from any such input (for example from a document). If the hash function is strong, it will not be feasible for anybody to reverse-engineer the input. At the same time, since the hash function always gives out the same result for a certain input, you can compare the resulting “fingerprints” - if they are the same, the input is still the same, if they are not, the input data was changed. This can be used to quickly verify if large datasets have been tampered with for example, or if they are original.

  2. Hash functions are used during (Proof of work) mining, when computers all around the world compete to be the first to guess the correct “target hash of the network”. At the moment I only very roughly understand this procedure and look forward to learning more.

  3. It means that a hash function should ideally never give out the same “fingerprint” for two different inputs.

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#1062

  1. A hash function is a special type of function that takes an input and creates a unique output. What’s special about it is that it’s practically impossible to figure out what the input was based on the output, but the validity of the output can be very easily verified.

  2. Hash functions are used to encode data from a previous block, so the new block can know for sure that the data being transferred over to it has not been modified in any way.

  3. Collision resistance means that no two inputs can give the same output.

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#1063
  1. Hash functions are functions with special properties that:
    a) take an unique input and gives a unique output
    b) Any change in the input will result in a completely different output
    c) You cannot determine what the input is given the output.

  1. Hash functions are used in bitcoin for every transaction and the output data is stored on the blockchain.

  2. Collision resistant means that each input will have its own unique hash. No two inputs can equal the same hash.