Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#1768

There is another important function for hash functions. Do you know which one? :slight_smile:

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#1769

Public keys are derived from private keys using the elliptic curve, but the public key is hashed to get the address :slight_smile:

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#1770

To be honest Iā€™m not sure. Its been a long time since I watched it :slight_smile:

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#1771

Miners are not breaking the collision resistance. They just calculate hashes below the threshold :slight_smile:

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#1772
  1. Functions to me means that each unique Input gives a unique Output, or so called ā€œFingerprintā€ for that function. Also Data Integrity is used to be sure the data is consistent and hasnā€™t been changed.

2.Bitcoin uses SHA-256 hashing to generate values to secure the transmission when the message (Bitcoin transaction) is intended for a particular recipient(s) only.

  1. Because hashing provides values for security, it is important that each unique input has a unique output and not duplicate or cause a ā€œCollisionā€ which may compromise the Data Integrity and security.
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#1773
  1. hash functions are a one way process where an input generates a unique output.
  2. in Bitcoin the hash function SHA-256 is used to hash transaction data and add new blocks to the chain.
  3. collision resistant means it is ā€œinfeasibleā€ or highly unlikely for 2 data sets(input) to produce the same unique output.
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#1774

Mining blocks :thinking:

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#1775

1/ hash functions produce an output based on an input whereby the output cannot determine the input
2/ hash functions in bitcoin use an algorithm called sha 256 to produce an output of fixed length
3/ collision-resistant refers to the difficulty of two inputs producing the same output

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#1776
  1. hash functions are algorhythms that represent some value (input) in hash numbers (output)
  2. sha 256
  3. it means that 2 inputs in a hash function is infeasible to have same outputs
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#1777

  1. Hash functions are functions where each unique input produces a unique output, and they are one-way functions, because you can go from input to output, but you canā€™t go from output to input.

  2. Hash functions are part of the block hashing algorithm, which is used to add unconfirmed transactions, plus the data related with time, into the blockchain through the mining process.

  3. By having different inputs, its very infeasible, or almost impossible, that we will have same output, and the most part of cases each input has different output, just need to be attentive on Birthday Paradox.

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#1778

  1. An algorithm that converts an input into a predetermined but non reversible hash. If even a single digit of the input is changed, the output will be completely different.

  2. Hash functions are used to maintain the integrity of the blockchain. Each block contains a hash of the previous blocks entire data. This way if a block is ever altered at all, it would be caught immediately because the hashes would not longer be correct in subsequent blocks.

  3. A collision resistant hash function has a low probability of two different inputs having the same output.

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#1779

  1. hash functions are one-way functions. Each unique input gives a unique output. Similar to a unique fingerprint for each input once it is output

  2. The sha-256 hash function is used with bitcoin when bitcoin transactions take place. this way every transaction is stored uniquely and canā€™t be falsified or altered after the transaction.

  3. If it is hard to find a hash function that has the same hash than it is collision-resistant.

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#1780

1.you put an input and get a special output which is unique just like a fingerprint.

2.in simple terms hashing means taking an input string of any length and giving out an output of fixed length . in the text of crypto currencies like bitcoin , the transactions are taken an input and run through a hashing algorithm a( bitcoin uses SHA-256 ) which gives an output of a fixed lengthā€¦

3.collision resistant is a property of cryptographic hash functions ; a hash function H is a collision resistant it is hard to find to inputs that hash to the same output that is two inputs and b such that H (b)=H(b), and a=/b every hash function with more inputs than outputs will neccessarly have collisions.

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#1781

A hash function is something that takes a set of data (of any length) as an input and outputs a hash of a fixed length. Each set of data has one unique hash.

SHA-256 is used in several different parts of the Bitcoin network: Mining uses SHA-256 as the Proof of Work algorithm. SHA-256 is also used in the creation of bitcoin addresses.

Collision Resistant means that two separate data sets should not create the same hash in normal circumstances. If a collision is possible with a normal data set, the hashing algorithm is not considered collision resistant. If an enormous data set is required in order to find a collision, the hashing algorithm is considered collision resistant.

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#1782

Thank you Alko, i think you are right :smiley:

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#1783

hash functions such as sha256 are very important in the world of encryption. they take an input and generate a value. the value will be, hopefully, unique to that string input and the input can be as long or short as you want. even if just one character is changed in the input the output will totally change

  1. hashing is used to finalize transactions and therefore they are used in the process of mining

  2. the birthday paradox aside a collision resistant hashing function is prefered. For complex blockchains we want to pick hashing algorithms that are most likely to produce unique outputs

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#1784

Homework on Hash Functions - Questions

Describe hash functions with your own words

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).

Answers: Used to create immutability with pointers and linked lists. A fair playing field to use brute force to compare Nonce difficulty rating to earn rewards.

What does it mean when we say that hash functions need to be collision resistant? (We didnā€™t use the term ā€œcollision resistantā€ in the lecture, but you will easily find this on Google, we add this question intentionally to make you research information on your own, thatā€™s how you learn best).

Answers: If the interval between blocks is too long problem solving among miners creates collisions of duplicate blocks. As well as as orphan blocks.

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#1785

  1. These are functions that convert the input of choice into fixed-length outputs.

  2. In Bitcoin, transactions are perceived as input that is run through the SHA256 hashing algorithm, which gives a fixed-length output.

  3. A collision happens when more than one input produces the same output. Collision resistance means that collision is unlikely, although not impossible, to take place.

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#1786

  1. Hash function give a unique output to every unique input.

  2. Miners process transactions through hash functions to verify them before adding them to the block chain.

  3. That you wonā€™t get the same output for different inputs.

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#1787

1 - Hash function is a process that makes an input to become a fixed cryptographic output by a mathematical algorithm

2 - Hash function is used in every transaction. The output data is store inside blockchain

3 - Hash function are programed to have colision resistance. That means that is very difficulty, almost impossible to make two inputs resulting in a same output

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