Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#2872
  1. Hash function is a one way cryptography where each unique input equals a unique output.
  2. It is the hashing algorithm used in Bitcoin mining.
  3. The collision resistance means it is difficult to find 2 inputs that produce the same output for the hash function.
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#2873
  1. Hash function takes input and creates unique output. It does not allow you to generate the input using the output. Even a small change in input results in a total different output.
  2. Each block data is converted to a hash, to ensure the data has not been changed. Then in proof of work a nonce is added and the resulting hash needs to meet certain requirements. The correct nonce can only be created by randomly guessing it.
  3. In cryptography, collision resistance is a property of cryptographic hash functions: a hash function H is collision-resistant if it is hard to find two inputs that hash to the same output;
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#2874
  1. There are multiple hash functions which contain different characteristics. They serve as a digital identity and typically only have one input for each one output. When data is changed on the input, it is different from what is outputted.
  2. Hash functions are utilized is crypto’s such as bitcoin by using the SHA 256 algorithm that keeps the protocol protected. The result of a function is called a hash.
  3. Hash functions need to be collision resistant, so they are not compromised. For example MD5 is a hash function that was figured out to be reversible therefore it is not collision resistant.
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#2875
  1. Hash functions are solved in a linear unidirectional manner, with unique inputs creating unique outputs
  2. They utilize block signatures from unique keys using timestamps and dates from previous transactions, which creates unique digital fingerprints.
  3. It is almost mathematically impossible to find two inputs that result in the same output.
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#2876

So basically a hash function is this complex function that takes some input, transforms that into bytes(i think), and transforms that into an output. SOMETHING LIKE THAT.

In bitcoin, each transaction’s hash output holds is based on all the transactions that have previously happened on the blockchain. So it quite impossible to hack (from my understanding) so it provides big security power!

From what I understand, collision resistance means a low probability of two random events to collide (for example two inputs to have the same output) so we need this in hash functions so that we dont get F*D by randomness :))

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#2877

  1. hash functions are basically digital fingerprints of data inputs. Each unique input makes its own unique output.

  2. hash functions are used to mine to transaction data, and verify that a transaction can be spent.

  3. collision resistant means that if you have 2 inputs and get hashes from them, those hashes will never be the same. The hashes may sometimes be the same but the probability of this is very low.

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#2878
  1. a hash function takes a unique input and converts it (digests it) into a unique output. any change in the original input would have created a uniquely different output.
  2. Bitcoin’s protocol compiles the input, which is all the transactions (7 per second) from the last 10 minutes (on average Bitcoin miners add a new block to the chain every 10 minutes) as well as the hash output from the previous block, and outputs a unique hash. rinse repeat!
  3. Collision Resistance describes the difficulty there would be in finding the exact unique inputs used to create a specific hash output.
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#2879

1 - Hash functions convert a input to a binary code, the result is processed through a intricate mathematical equation and then the result in converted in a hexadecimal representation. That is the 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.
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 - A hash function is collision resistant if it is hard to find two inputs that hash to the same output.
The harder they are to find, the more cryptographically secure the hash is.

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#2880

It means that it is unlikely that ‘different’ inputs won’t produce the same hash (output)

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#2881
  1. hash function is used to create a digital fingerprint of the input.
  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. In bitcoin mining, the inputs for the function are all of the most recent, not-yet-confirmed transactions
  3. This means that two different inputs won’t give you the same output fingerprint
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#2882

unlikely or impossible? I wonder?

#2883
  1. It’s function which allow to encrypt the data.
  2. They make a link between the blocks.
  3. It’s hard to find two input which will produce the same output.
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#2884

1 Mathematical one-way algorithmic-function, that you can use for encrypting a piece of data, from an initial data to the digital fingerprint of it.
2 Bitcoin transactions are hashed with SHA 256. Miners are searching for a correct nounce than adding the hash of the last block they can hash a new transaction.
3 Collision free means that two different inputs can never give you the same output hash

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#2885 
  1. Describe hash functions with your own words

a mathematical algorithm that maps data. A One way output function, making it feasible to revert.

  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).

Inputs to a function is used to hash transaction data.
Usually for determining Private keys, Public keys(address), Used to sign transactions.
Also used for proof-of-work.(mining) for new blocks added to the blockchain.

  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).

collision resistance is a property of cryptographic hash functions:

  • if it is hard to find two inputs that hash to the same output; that is, two inputs a and b where a ≠ b
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#2887

1.- It’s a function that produces an unique output, where the output is a fingerprint of the input and it cannot be reversed, this means with the output we cannot know what the input was.

2.- It is used to write new transactions in the blockchain.

3.- It means it is hard to find two inputs that hash to the same output.

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#2888

  1. Unique Fingerprint, works in only one direction.

  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. a hash function H is collision - resistant if it is hard to find two inputs that hash to the same output;

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#2889

1 hash input is like a fingerprint.
2 sha 256 input, makes it very secure.
3 same input should never have different outcome.

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#2890

  1. Hash function is an algorithm where an input produces a unique output.

  2. In cryptocurrencies, hash functions allow security

  3. It means that it’s hard for two input to hash the same output

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#2891

Its the other way around, meaning its highly unlikely for two inputs to result in the same output. :slight_smile:

#2892

  1. They encrypt data and make transactions traceable

  2. to create private and public keys

  3. two inputs create a unique output which is not reversible, two inputs transforming into the same output does not work

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