Homework on Hash Functions - Questions

[tcoltman]

• Describe hash functions with your own words
  Its a function where any input value can be transformed to a long hash value which is the digital finger print
• How are hash functions used in cryptocurrencies like bitcoin?
  In Bitcoin the Hash function is used to hash transaction data. Also mining and finding a nonce requires finding a number that generates a specified hash in combination with data unique to that block. By creating addresses, private and public keys. Transforming transactions which can be recorded as hashes in a ledger.
• What does it mean when we say that hash functions need to be collision resistant?
  two different inputs should not give the same output

[tanyiakandohla]

1 Hash Function
Secure algorithm which converts a message (input) to a string of digits. It’s is deterministic in that the output is unique to the input message. It is infeasible in that no 2 inputs could have the same output and no output could be used to determine or decipher the input. This can be described as its “one way” property.

2 How are hash functions in used in cryptocurrency
The hash functions are to generate the transaction information sender, address, value and information. They provide security and anonymity.

3 Collision resistant hash functions
No 2 has functions will be the same.

[wafflemakr]

@CeesQ

haven’t researched it, but what first pops to mind is that a bitcoin address is a hash function from the mnemonic phrase you typically get when installing a wallet.

@HoS

Hashing in bitcoin, SHA 256, takes any input data (transaction) and generates a hash with a specific length.

@Experimentation

The hash function provides the necessary information regarding date, difficulty, block ID etc.

@BohemianJC

Hash functions are used in crytpocurrencies like bitcoin because they can hash transactions creating unique outputs which can’t be reversed.

@MrHunk

The input goes through a hashing algorithm is you get an output with a fixed length.

Hello guys! Maybe you can dig a little bit more into the mining process and how blocks are chained together.

[wafflemakr]

Amazing answer timl! Keep up the great work!

Felipe.

[pbrandstater]

1. Hash function converts characters of any length and converts using a hash algorithm to specific length.

2. Bitcoin blocks are generated on the average every 10 minutes . As far as reverse engineering, the idea of SHA-256 is there’s no way to go backwards to find a valid nonce

3. It’s vital that two different inputs don’t have the same hash output; this is imperative to digital safety. While mathematically this is possible, it’s best if the odds are astronomically long for two different inputs to end up with the same output. In the event two distinct inputs have the same output, it’s referred to as a cryptographic hash collision, making it imperative for a hash to have a strong collision resistance. Otherwise, the algorithm will be vulnerable to collision attacks

[wafflemakr]

Hi @Gabriel_Ng! How about question #3?

[wafflemakr]

You really did your homework!! Congratulations!

Felipe.

[wafflemakr]

Hi there!!

@Euphorical

. (Maybe…?)

Yeah, you get the idea. Basically, is a one way function!

@Euphorical

They are used to prove blocks are legitimate & to show that the senders do in fact have the funds to cover the transaction.

You can search how these hash functions are used in bitcoin mining process.

[CocoaCrypto]

1- Hash functions are the inputting of data to the result of a specific set of output unique to that input only! If you have a large set of data, it can condense it into an output of the same length every time, and if you have a small data set, it helps you keep track of whether or not any changes whatsoever have been made to that data. Hash functions work the same way, no matter how big or small the input is.

2- In bitcoin, the hash functions are what are used to mine bitcoin, or rather, they are used to write new transactions onto the blockchain during the mining process. In this case, the inputs for the function are all of the unconfirmed transactions. The hash rate is how fast or slow miners are able to input hashes. The higher the hash rate, the more people and machines are involved, and the smoother the process goes! If the hash rate is low, this means the difficulty of solving has increased too much and must be adjusted.

3-Collision occurs when 2 different inputs result in the SAME output hash. This is problematic if you are trying to determine the integrity of the input! Therefore, collision resistance is extremely important, although there is a minuscule chance of collision actually happening.

[AJade]

1. Describe hash functions with your own words. A function that can take a unique input of any length and produce a unique output of a predetermined length.

2. How are hash functions used in cryptocurrencies like bitcoin? They are used to provide a secure system of record that is immutable and continually verify that no data was tampered with in the blockchain by validating the digital fingerprint.

3. What does it mean when we say that hash functions need to be collision resistant?
   Hash functions should have a very low probability of producing the same digital fingerprint from different inputs.

[mikekai]

1. A hash function takes an input and creates a unique output that is predetermined but resistant to identifying what the input is from the output.
2. Hash functions are used to give a fingerprint to a transaction and to verify the information in all of the transactions. Like in the merkle root in the block header. It is also used as a sort of security to the data as one small change will change the block before it and the block before that one. This is a way to detect tampering. It’s also part of the proof of work.
3. They need to have a reduced possibility that two identical hashes will be outputted.

[Javchisau]

1. Hash Function: It is a process where a each input produce a unique output. It is like a 'fingertip" .
2. A hash function used in Bitcoin is called: SHA 256. This gives an output of fixed length. I does not matter how small or big the input is, the output will always have a fixed 256 Bits length. If there is a big amount of data in the transaction, instead of remembering the input data, it is better to just remember the Hash in order to keep track.
3. “a hash function is collision resistant if it is hard to find two inputs that hash to the same output”. It is impossible to find out the input coming from the output. It is “ONE WAY FUNCTION”. It never goes from output to input. Hash Function is one way to enable security during the process of message transmission when the message intended only for a particular recipient. In fact, the analysis of an input through a hash function will always be the same. Having a different hashes every time, it is impossible to keep track of the input. It is a fast operation and very efficient system.

[Hamze_Dirir]

Thank you for your kind words buddy.

Hamze

[RLion]

Homework on Hash Functions - Questions

Describe hash functions with your own words

• Hash function is a complex calculation (SHA-256) from a known input, The result is a caclculated value from the function

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 to hash a block of bitcoin transactions to create a new hashed value which will be used for the next block.

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 resistant mean that never a same output is expected from a hashed block

[Gabriel_Ng]

Sorry i missed it out.
3. Collision resistant means that for two different inputs to get the same hash should not happen. It is mathematically possible but the numbers are so astronomically long that the result to have this problem is very unlikely.

[coffy]

@Alko89

• Special functions which output is really, really hard to link back to its output.
• Many things from deriving public keys to block signatures, verifying if an unspent transaction can be spent by a specific key and much more.
• Most hash functions are not really collision resistant. But it basically means that you get the same output for two or more different inputs (which is also really, really hard to achieve).

Completely agree with this answer

[abull]

• Describe hash functions with your own words
  A: Hash functions are one-way functions where it is impossible to figure out the input from the 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).
  A: Hash functions are part of bitcoin’s block hashing algorithm. By solving this algorithm new transactions are confirmed and added to the blockchain. As payment for solving this algorithm (mining) the miner is rewarded with bitcoin (the block reward).

• 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 functions need to be collision resistant because if they are not, the validity of digital signatures is destroyed and a transaction’s authenticity cannot be trusted. If collisions (where 2 different inputs creates the same output) are easy to find, a signature/transaction could be faked and the security of the blockchain ledger could be compromised.

[Cryptojuice]

1. a hash function is a one way mathmatic equation that takes binary input data and outputs a unique, consistant, hexadecimal number. It 's properties make it useful as a “digital fingerprint” .

2. Mining uses SHA-256 as the Proof of work algorithm. It’s also used in the creation of BTC addresses lending privacy and security.

3. Two different inputs shouldn’t produce the same output hash

[Gemstar]

1. Hash functions are one-way functions where each unique input is converted into a unique fixed 256-bit output (digital fingerprint), and anything modified in original data set will create a different string of alphanumerical value. This process can’t be reversed, i.e. impossible to get original input data from output.

2. Hash function keeps BTC secure by encrypting transaction data: Hashing is used to codify inputs of transactions that contain each block in the chain, which becomes a vital part of subsequent blocks, i.e. hash of previous block is contained in current block. SHA-256 can also function as a data-integrity check since an attempt to manipulate the data or alter info in a previous block changes the hash of that block, breaks the chain and makes the block invalid, unless you’re able to recalculate all hashed data in previous blocks.

3. Collision-resistant means there’s a very low probability that two inputs will generate the same output hash, which is vital in cryptographic hash functions.

[SimonO]

1. Hash functions take a string (both letters and numbers) of any length and transform it into a unique output of a fixed length.

2. For cryptocurrencies, hash functions are used in the mining process in order to add new blocks of transactions/states to the blockchain. Since each block contains a hash of the previous block + nonce, this effectively links all blocks and makes all their historic transactions immutable since any minute change of one block would radically change the hash output of the blocks thereafter, which would easily be picked up by the network.

3. Collision resistance of hash functions means that different inputs may not render the same output.