Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#461

  1. Hash function is a one way function that us used to generate a unique digital fingerprint of a specified input.

  2. It is used to hash transaction data into encrypted information.

  3. To make it impossible to find to inputs that create the same output.

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#462

  1. A hash function changes an input into a unique output. It is irreversible and can be compared to a digital unique fingerprint of the input.

  2. In BTC hash functions are used to provide a unique fingerprint of transactions on the network. Each block hash is linked with its parent block, Changing any transaction in a block will change the hash of that block and the network will reject it by consensus. A miner needs to carry out lots of hashing in order to guess the number required to find a block.

3.Collision resistance means that it is infeasible that two different inputs could have the same hash. It is a function of security of the network.

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#463

  1. Describe hash functions with your own words
    A hash function takes a unique input and generates a unique output of a fixed length.

  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 to write new transactions to the blockchain through the mining process.

  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).
    This refers to the birthday paradox. You have a 1/365 chance (way less than 1%) of meeting any random stranger on the sidewalk who has your birthday. But if you put 30 people in a room together there is a 50-50 chance they share the same birthday. With a 128bit hash, you would have a 50% chance of a collision at 2 to the 64th. In other words, a really long time. With a 256 bit number (a number so large) it is safe to assume you won’t run into a collision. Not impossible, but infeasible.

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#464

  1. Describe hash functions with your own words
    A function where you cannot figure out the input used to get the output.

  2. How are hash functions used in cryptocurrencies like bitcoin?
    They are used to mine bitcoin. The difficulty changes so that it takes miners approximately 10 minutes to solve the problem.

  3. What does it mean when we say that hash functions need to be collision resistant? It means that they need to be resistant to the exponential probability of being solved when more people/nodes begin to try and solve the problem.

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#465
  1. Hash Functions are one way functions that with a unique input gives a unit output.

2.By running an algorithm that produce a unique digital output known as hash.

3.That is very hard to find two inputs that hash the same input.

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#466

1 - A hash function is a function that is used in order to produce a unique fingerprint for a data set. A hash function therefore takes an input and passes an output. The input should never be able to be calculated from the output as this would destroy the security of the hash function.

2 - Hash functions are used in cryptocurrencies such as bitcoin in order to link all the data together such that any variation on any previous data would result in a massive change in all subsequent hashes. This change in the hashes is how a node would detect if the new block was fraudulent and would then be rejected. The Hash function is also part of the mining process as it is what the miners are computing in order to add a secure block to the blockchain.

3 - Collision resistance is a feature of hash functions that says that although not impossible it is very difficult to find two sets of separate input data that produce the same hash.

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#467
  1. a cryptographic function that returns a unique fingerprint of any arbitrary data.
  2. to prove data was not modified and to be used as the basis of the puzzle required to “solve” a block.
  3. Collision resistance is the possibility of 2 inputs to a hash function producing the same output (fingerprint).
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#468

  1. Hash functions are functions where you set an input and get a special identification code, the identification code changes completely if you change the input. It is almost impossible to find the input if we try to decipher the identification code.

  2. Hash functions in bitcoins are used to implement new transactions to the blockchain by mining bitcoin.

  3. It means that it is almost impossible to find two identical outputs.

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#469

  1. It’s a formula where for each input applied you get an unique output

  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. If a hash function is not collision-resistant then an attacker can break the function with little effort. But if it is collision resistant then it gets really hard to find two inputs for the same output.

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#470

Got It and TY very much for the clarification

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#471
  1. Describe hash functions with your own words

A hash function is a one way computation that, given an input, produces a fingerprint for it.

  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).

They are used in the mining process (in proof of work), and also to sign transactions inside a 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).

It means that it needs to be highly improbable that two inputs produce the same output.

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#472

  1. Describe hash functions with your own words.
    Hash functions generate a unique output with an untraceable input.

  2. How are hash functions used in cryptocurrencies like bitcoin?
    Integrity in the blockchain is assured by hash functions, meaning that fresh Bitcoin are only created through mining and therefore making fraud infeasible.

  3. What does it mean when we say that hash functions need to be collision resistant?
    For security purposes, the higher the chances of finding the same input (i.e., the chance of collision), the lower the resistance. H(A) = H(B), then A = B.

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#473

1.Describe hash functions with your own words
A hash function is an oneway function where the output is unique and will tottaly change is theres is the slightes change in 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 is used in mining of bitcoin and to creating bitcoins adresses and keys.

** 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).**
That the likelihood of two different inputs produces the same output needs to be extremely low.

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#474
  1. a hash function has a unique output based on the input. One can not go from output to input.
    2.Hash functions are used to secure the blockchain, the last transaction acts as part of the input along with the private keys and public keys. together they create a unique output.
  2. collisions resistance means that it is very improbable that 2 inputs would produce the same output.
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#475

  1. Hash functions are functions that produce a unique output (of 256 bits) for every input but the output does not produce the input in question. In using a hash functions you can produce a unique signature for each piece of data that adds to the “immutability” aspect of a blockchain.

  2. Each transaction is hashed which is then built into the hash of the next transaction that follows in the blockchain, thereby creating an immutable chain.

  3. So it is actually not impossible for two inputs to have the same output, however it requires a huge number of attempts to find two inputs that have the same output when dealing with 256-bit hashes that it becomes virtually impossible, however not technically impossible.

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#476

Hash functions are mathematical equations that take in, instead of numbers, pieces of text, of many lengths and convert them into a line of text of fixed length.

Mining requires the solving of these hash functions. When a solution is found, a block is produced. Each block contains 12.5 BTC.

Collision resistant means that for each input, one distinct output is produced.

#477

  1. Every input always generates a unique output and every hash function should only go
    from input to output to create value and security.

  2. Bitcoin hash functions anything into a unique output of a fixed length.

  3. It should be very difficult for any hash to represent more than one input.

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#478

1 Data encrypted by SHA 256 language gives a string output of fixed length aka Hashed and can not be reversed
2 Hash is used to encrypt and provides the security for b/chain
3 Inputs give different outputs if hashed so no same input string can give a different output if hashed repeatedly

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#479

[quote=“ivan, post:1, topic:8430, full:true”]
Homework on Hash Functions - Questions

1. Describe hash functions with your own words

Cryptographic hash functions are a complex mathematical operation/protocols run on a digital data.
A hash function is simply a one way function that takes a unique Input value to generate/hash a unique Output, which is a digital fingerprint of the of the Input.

As an example, a hash function takes an Input (which can be data, files, units of value, numbers etc however large) and computates/generates/hashes an Output (fingerprint of the Input). The Output hash is usually displayed as a hexadecimal alphanumeric or a predefined size .

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

Hashing Functions are an essential part of cyber security and some cryptocurrencies like Bitcoin.
The Bitcoin protocols uses the SHA256 (Secure Hash Algorithm 256) as an underlining cryptographic hash function, incidentally designed by US NSA in 2001.

Using SHA-256, Bitcoin miners start the process by which blocks or transactions are verified and added to a blockchain.
In bitcoin Hashing function is used to make a digital fingerprint of the Input data. Every block on the blockchain gets hashed and every block also contains the hash of the previous block, which makes every block cryptographically linked together. Once a block is validated (mined), no one can alter any digit/data of a transaction in an older (historic) block, this effort will be denied and neglected by all the corresponding network of nodes.

as an example: As the hash Output is a digital finger print of the Input data, so therefore from a human finger print we can not produce a human, so from a hashed digital Output you can not create/replicate the original digital Input, hence it is a one way flow only.

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

A collision in this instance is when more than one Inputs generates the same exact hash Output. No hash function is collision resistant, but finding a collision is mathematically extremely hard and would take a long time.

A Hash Collision attack is an attempt by hackers to find two input strings of a hash function that produce the same hash Output, because hash functions have infinite input length and a predefined output length, there is inevitably going to be a lucky chance and a possibility of two different inputs that produce the same output hash. If two separate inputs produce the same hash output, it is called a collision, and that would be damaging the bitcoin protocol as we know it.

Cryptographic hash functions like SHA256 are usually designed to be collision resistant, currently the odds of a collision are very low or indefeasible, especially with very large output sizes. However as available computational power comes to play like the Quantum computers of the future, can increases the ability to brute force and therefore hash collisions could become more and more feasible.

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#480
  1. unique verification string output for every unuque input
  2. in mining process to verify the transaction i.e. proof of work
  3. you can not have/use the ouput and successfully decrypt the input