Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#3176
  1. hash-fct map an input to an output, but the reverse mapping is not possible
  2. the hash-fct SHA-256 is used by miners to produces hashes which have to be below a target value (set by the difficulty level) for a new block to be added. the irreversability of the SHA-256 hash algorithm means that one cannot work backwards from the target. New blocks are also linked to the previous block by including some of their data in the hashing for the new block, creating immutability.
  3. a collision means that two different inputs produce the same hash. collision resistance means this has to astronomically unlikely.
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#3177
  1. A hash function runs a series of functions on an input that creates a complex output.
  2. A hash function allows for individuality and assignment of value to entities by creating an identity for a transaction that cannot be duplicated and therefor, whoever owns the output (which can be verified mathematically) owns the transaction.
  3. I vaguely understand the concept, however it is not gelling with me. While it is possible to have the same output for two different inputs by random chance, the chance is so slim that they will ā€˜collideā€™ that it is not reasonable to search for it.
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#3178

  • Describe hash functions with your own words
    fingerprint that thru inputs generate unique outputs

  • 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). This should be part of the mining process in which thru a unique output bitcoin in mine is validated with this unique fingerprint.

  • 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). This is when to different inputs generate same output.

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#3179

1Describe hash functions with your own words .
Each unique input will give a unique output , one directional , and canā€™t figure out 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).
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? (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).

Collision resistant prevents an attacker from creating 2 distinct documents with the same hash.

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#3180

We donā€™t use hash functions like SHA256 to derive public keys. For that the elliptic curve function is used.

Not referring to public keys an input to a hash function can be anything and its important to be very difficult to find the same output. :slight_smile:

#3181

A transaction hash is basically just a txid that is used to uniquely identify a tx. More important hash functions are used in the block hashing algorithm or mining. :slight_smile:

#3182
    1. A hash function is a piece of code which converts data into a bunch of random numbers and letters known as a hash. The hash can be used to verify that information in the blockchain is correct.
  2. Really struggling to express the question lol
  3. Collision resistance means that it will be impossible for 2 outputs to be the same.
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#3183

A hash function gives a unique fingerprint for any input, always producing a unique number which can not be inversed. There is no way to figure out the input by knowing the output

#3184
  1. Describe hash functions with your own words

A hash function is something that transform any digits any typing of a phrase into a unreadable code which you never can trace back when you use SHA256

  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).

Maybe they hash any transaction or the (owner) of the transactions like the guy who send the Bitcoin

  1. 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).

It means a one way function an input causes a unique output and you cannot find out what the input was.

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#3185

What is difficult about the question? :slight_smile:

#3186

What about the rest of the homework? :wink:

#3187

A) Hash function is an mathmatical algorithim the has a fixed output
A) Each new hash added to the chain will create a new verified block and the information from previous blocks cannot be altered
A) if two seperate inputs are provided the output must be different ( i believe this is made possible by higher bit algorithms)??

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#3188

Describe hash functions with your own words
Hash functions help keep the blockchain (and other things) safe and secure. This is because each unique input creates a unique output and you cannot go from an output to an input, if you can then the hash function is compromised and should not be used.

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 mining to produce and verify blocks to be added to the blockchain. Mining software needs to hash the blocks header and aims to get it equal to or lower than the target which is a 256 bit alphanumeric code.

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).
Collision resistance is where two inputs have the same output.

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#3189
  1. Hash functions is a one way string of data that is fixed to a given output (digital fingerprint).
  2. Cryptographic hash functions are used to make it more difficult to detect the contents of a message or information about a recipient or sender.
  3. Collision resistant means that two input hash should map to the same output. Thus, making it unlikely that the hash function gets the same output.
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#3190

Not sure what you mean by that. It simply means the probability for two inputs to have the same output because the number of inputs (basically infinite) is always larger than the number of outputs (2^256 in SHA256) each hash function is bound to have collisions. :slight_smile:

#3191
  1. a Hash function is a one way repeatable function, which means it is not reversible and same input always gives same output
  2. Miners combine transaction and other info in many different ways until the hash of that combination starts with n 0ā€™s
  3. that 2 inputs cannot give the same output
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#3192

Hash functions are one way functions, from the same input you get alyays the same output, but you canā€™t deduct the input from the output. SHA-256 is used by Bitcoin. SHA-256 was created by NSA. Exactly the same way raw meat that become mince, the same way any number, any piece of data is transformed into random numbers. Any change into input leads to a completely different output. Same input produces same output.
2.
Hash functioms are at the foundation of cryptocurrencies. They are used to encrypt user passphrase, all transactions, create addresses and sign digitally any instruction to move crypto currency.
3.
If somebody tries to move same 1 bitcoin in the market to 2 different person wallets, only one person will get the bitcoin in the end, avoiding duplicating and corrupting the data. This is achieved by the network nodes that will try to push data from memory pool to ledger file by computing the hashes for the transaction. When 2 nodes compete to push the transaction data to the ledger data, the first one that succeedes will spread the results to other nodes. Once the data is in the ledger, the other nodes will take the data as correct. The other nodes data will be dropped. This way only one person gets the bitcoin. The other gets nothing

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#3193

Collision resistance in hash functions simply means that its difficult for two inputs to result in the same output. Iā€™m not entirely sure what would happen in case two txid would end up being the same :thinking:

#3194
  1. A mathematical function that puts out a unique 256 bit hexadecimal number for any input using an irreversible process.
  2. They are used as part of the block chain development method to encrypt the private and public keys used as well as in the proof of work process in mining.
  3. A hash function is collision resistant if it is hard to find two inputs that hash to the same output.
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#3195

Homework on Hash Functions - Questions

1. Describe hash functions with your own words
Hash functions are complex mathematical equations that produces a unique output for each input, which cannot be reversed to discover the original input based on 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).
Bitcoin uses a proof of work hash function called hashcash to write new transactions to the blockchain through mining.

3. What does it mean when we say that hash functions need to be collision resistant?
Collision resistance means two unique inputs cannot lead to an identical output.

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