Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#3377

  1. Describe hash functions with your own words. - Hash functions are unidirectional functions where each unique input creates a unique output. The output can be thought of as the digital fingerprint of the input.

  2. How are hash functions used in cryptocurrencies like bitcoin? - Cryptocurrencies use hash functions to pass transaction information anonymously.They are also used for speed and efficiency in the retrieval of information.

  3. What does it mean when we say that hash functions need to be collision resistant? - Collision Resistance means that no two inputs will generate the same output hashes.

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#3378
  1. hash functions are functions that give data a unique fingerprint

2.hash functions provide security with a one way function that is uniquely tide to the input data. in the case of crypto the hash function give bitcoin its security. then proof of work with mining and verifying all transactions to provide blocks to a chain with every new transaction

3.In order for hash function to be collision resistant the hash function can not have two different inputs for the same hash.

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#3379

  1. Describe hash functions with your own word
    Hash function take data, breaks it down to binary and then does a bunch of calculations with it and puts out a fingerprint which is unique to the original data

  2. How are hash functions used in cryptocurrencies like bitcoin?
    To pass information anonymously

  3. What does it mean we say that hash function needs to be collision resistant?
    It means that there can`t be two different inputs that result in the same output

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#3380

Hash functions only create a fingerprint of the data. Its not the same as public key cryptography where you can decrypt the output back to the input. :slight_smile:

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#3381
  1. Each unique input will give a unique output which is a unique fingerprint and only correlates with that specific input
  2. hash functions** are part of the block hashing algorithm which is used to write new transactions into the blockchain through the mining process
  3. is a property of cryptographic hash functions: a hash function is collision resistant if it is hard to find two inputs that hash to the same output
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#3382
  1. A hash function is a one way function which gives a unique 256 digit output.
  2. Hash function is used in Bitcoin mining and is the primary encryption which make bitcoin safe. Bitcoin use hash function SHA-256
  3. Collision resistant hash means that it is almost impossible to find to different input producing the same output.
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#3383
  1. Unique one way functions.
  2. That’s because is part of the mining process and miners responsibility: the miners pick some transactions up and using them as part of the input, they try to calculate a hash function to provide a new block to the chain.
  3. The collision resistance requires that two different input messages should not hash to the same output.
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#3384

Hash functions basically gerenates unique “digital fingerprints” of the input. This is a one way function, there is no way to reverse the hash back to the input.

Hash function in bitcoin is used to hash transaction data into the blockchain.

collision resistant means that if there is an identical input, the hash in the output won’t be the same.

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#3385

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

  1. Describe hash functions with your own words
    A hash function is a mathematical function that converts a numerical input value into another compressed numerical value. The input to the hash function is of arbitrary length but output is always of fixed length ⟹each unique input gives a unique output, and hash function is one-way function.

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

In Bitcoin’s blockchain hashes are much more significant and are much more complicated because it uses one-way hash functions like SHA-256 which are very difficult to break.

This particular hash function is used because of these properties:

Unique hash value: For every input, it produces a unique output
High hashing speed: For each given input the computation is fast.
Secure hash function: It is almost computationally infeasible to reverse the function and make it two-way.

Bitcoin is simply a digital ledger of hashes that utilizes proof of work combined with SHA-256 to obtain mathematical traceability and unbreakability.

The process through which this is ensured is called "Bitcoin mining " that utilizes Bitcoin hashes generated through SHA-256 function at various steps of mining.

  1. What does it mean when we say that hash functions need to be collision resistant?
    Collision resistance plays a important role in providing message integrity
    In context of digital signing it’s hard to find 2 inputs that actually map to the same output, hard to find a colliding pair of inputs.
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#3386
  1. Describe hash functions with your own words
    • A function that creates a Unique output for any given input. In crypto they are one-way functions.
  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 hashes each and every transaction in the blockchain, resulting in traceability and Immutability!
    • Auditable
    • The “chain” contains hashes of previous blocks…
  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 is collision-resistant if it is hard to find two inputs that hash to the same output
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#3387

So i have a Question: How come indexing is not a viable way to break the SHA256? Logically it would take a lot of work and time but in theory it should be a viable method? I hope someone can help, thanks a lot!

#3388

  1. Describe hash functions with your own words
    A hash function creates a unique output based on a unique input. This is one-way; the input cannot be found with the output.

  2. How are hash functions used in cryptocurrencies like bitcoin?
    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. What does it mean when we say that hash functions need to be collision resistant?
    A hash function is collision-resistant if it is hard to find two inputs that hash to the same output.

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#3389

  1. Describe hash functions with your own words
    It is a one way function, x input is added to the function and a unic alphanumerical outpout it is created, it is not possible go from the output to the input which make the hash function incorruptible

  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 funtion are part of the block hashing algorithm which is used to write new transactions into the blockchain through the mining process
    The hash funtion converts an input of letters and numbers into an encrypted output of a fixed length

  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 bestt).
    Very low probability that 2 different inputs produce the same output

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#3390 
1. Describe the concept of public and private key with your own words.
	○ Random number generated by your computer is your private key 
	○ The private key is then run thru a formula (one-way function) to create a public key (derived from Private key)
	
2. What 2 use-cases can public key cryptography be used for?
	○ Public key cryptography use cases-
		○ For encryption
		○ Digital signatures
			§ Identify yourself
			§Ensure integrity of message
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#3391
  1. Describe hash functions with your own words
  • linear progress to make a unique fingerprint. Hash is ”the cryptographic blender” to greate the output data. Cryptpgraphic result which ingludes all original data
  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).
  • bitcoin protocol in mining searches certain numbers and letters to match with the output result. letter -to be able to create a new string/chain
  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).
  • number/amount of inputs and outputs need to be equal.
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#3392

  1. Hash functions are functions that take an input and give you a fingerprint output.

  2. Hash functions are used in Bitcoin for mining (proof of work) powerful computers will constantly generate hashes until they match up with both the input and output. This leads to creating a new block on the Blockchain resulting in the miner being rewarded with new bitcoin.

  3. Hash functions are collision resistant so similar inputs are unrecognizable from each other when turned into an output. One reason for this is so you can easily tell if a file as been tampered with.

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#3393

  • Describe hash functions with your own words
    Hash functions are functions in which each unique input produces a unique output, using the same input will produce the same 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).
    They are used to mine new blocks to add the the chain.

  • 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 means that it is hard for you to find two inputs that will provide the same output of the function.

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#3394
  1. a unique, input only calculatable translation of a digital input
  2. to encrypt and identify absolute individual transactions and coin locations
  3. each input creates a unique, unduplicatable output
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#3395

You’re right, but you posted your answer in the wrong thread :smile:

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#3396

Its impossible to have the same number if inputs and outputs. The possible inputs to a hash function is basically infinite and the number of possible outputs in SHA256 is 2^256. Because of this reason a hash function is bound to have collisions which is when two inputs result in the same output but because the number of possible outputs is so large the probability for this happening is extremely low. :slight_smile:

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