Homework on Hash Functions - Questions

[EvanErickson]

@ivan

1. Describe hash functions with your own words

A way to change the output and disguise the input of certain characters.

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).
   Mining and for new transactions

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).

It is very hard to have two different inputs get the same output

[LilPepeElJefe]

1. Hash functions are one-way functions where each input produces and output but it can’t do it the other wat around.

2. In Bitcoin has functions are used when creating addresses and public/private keys. Used in mining blocks to verify transactions.

3.Low probability that two inputs will produce the same output.

[DanDan]

• Describe hash functions with your own words
  A Hash Function is a function that takes a set of values, numbers or letters and turns it into a unique fixed length output of letters and numbers called a hash value.

• How are hash functions used in cryptocurrencies like bitcoin?
  Hash functions are used in bitcoin to secure transaction data. Blocks are made up of transaction data that is then hashed, each hash also includes the previous hash value, thus creating the chain of blocks.

• What does it mean when we say that hash functions need to be collision resistant?
  This is essentially where 2 different inputs have provided the same output.

[Narnia]

Describe hash functions with your own words
A hash function mathematically processes inputs of any length and returns unique outputs of a fixed length.

How are hash functions used in cryptocurrencies like bitcoin?
Hash functions are part of the block hashing algorithm which is used to write new transactions into the blockchain, the permanent record of all previous transactions, through the mining process. In bitcoin mining, the inputs for these functions include the most recent, but not yet confirmed transactions along with additional inputs like a reference to the previous block and the timestamp.

What does it mean when we say that hash functions need to be collision resistant?
In hash functions, a collision is when an attacker can find two inputs that both map to the same output. So collision resistance is important for security and means that each input has its own unique hash output.

[Zon14]

1. Describe hash functions with your own words
A hash function is a one way function. This means that each unique input creates a unique output. If the slightest thing is changed in the input it will create a totally different 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 in cryptocurrencies like bitcoin are used for security purposes and constitute the backbone of crypto security. A hash function turns a random input of data into a string of bytes with a fixed length and structure. The hash of a transaction makes it easy to identify transactions on 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).
Hash functions need to be collision resistant in order to protect the function. If a hash function is not collision resistant it is easy for an attacker to find multiple messages which produce the same hash.

[DJaySplash]

Hash functions are functions in which you put an input of data and the function encodes it to become a certain output of letters and numbers.

Hash functions are used in Bitcoin to mine blocks for the chain. When miners match the hash the blocks header is looking for it creates a block and rewards the miner with coin. This requires a lot of computation and work thus proof of work is born.

There cant be two of the same hash outputs for two different inputs

[Gremillion]

1. Hash functions are an equation used to create indecipherable output from the input given.

2. From what I can tell it is used to create specific blocks that are able to show proof of work for miners.

3. Each output is unique to each input. No two inputs will have the same output.

[kimberleyk]

1. Hash creates a unique digital fingerprint which cannot be recreated with alternate input. The data cannot be reversed as it is unidirectional. Input cannot be determined by output.
2. Cryptographic hash functionality is used for security. They are quick in terms of computation & deterministic.
3. It’s almost impossible to generate the same output with 2 or more different inputs.

[Francisco_Sifontes]

1. Describe hash functions with your own words.

A hash functions is a function given to any input to produce a hash . This hash, depending on the algorithm is a string of alpha numerical letters and numbers that associates the unique input given by the user.

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 used in cryptocurrencies like bitcoin to secure the input data (a transaction in bitcoin case) that cannot be reversed, or tampered and cannot go back even with the hash . Each hash in bitcoin is unique to the input that was done in the first place. Since it cannot be reversed and it is now part of the blockchain , the hash is totally secure.

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 function is collision resistant when there are no 2 inputs that give out the same hash.

[Gabriela]

1. Hush function is an algorithm that each time produces unique output. However having this unique output, it cannot reverse it to receive initial data (input).

2. It is used to write new transactions into the blockchain through the mining process.

3. It means that it should not lead to the situation in which two inputs can be hash to the same output. output.

[mandorlino]

1. Hash functions take an input of any length (a text, a number) and give as an output a seemingly completely unrelated number. This number, however always has the same amount of digits, no matter the input. Let’s call it an unique ID.

Every time that the same input is fed to the hash rate, the hash rate will give the same unique ID. However, the slightest change to the first input will give a completely different ID: yes, the string will have the same amount of digits, but it will bear no resemblance whatsoever to the first ID, nor to any of the inputs.

Hash functions are designed to be so complex that it is impossible to deduct the input from the output, except for the use of brute force: to try every single possibility as an input until the same output is given.

We can think of the output or ID as a fingerprint because it is really unique to the input. Therefore, a good hash rate should never give the same output for two different inputs. This way, you wouldn’t need to know a person at all to be able to identify that they touched two different objects.

Hash functions are crucial for digital security, as they allow checking that a given text or number matches another one without even having a clue of what text or number is. This is why most applications make you change your password if you forget it: they don’t know your password (input), they just know the hash of it (output). If you cannot replicate that hash, then you must create a new password.

2. In the cryptoverse, hash functions are crucial, as they allow connecting each block of transactions to the next one and at the same time guarantee that the previous block hasn’t been tampered or modified.

Each block contains the hash of the previous one. If the previous block were to be modified, then its hash would not match the next block, or actually any block at all.

3. Hash functions need to give a different output for every input, otherwise, not only the outputs would stop working as unique IDs, but it would make it easier for someone to figure out the “secret” of the hash function and reverse engineer its conversion process. If two inputs give the same output, we call this a collision. Therefore, a hash function needs to be collision resistant.

[Niek604]

1. hash function convert a specific input to a unique specific output
2. uses the hash function for your keys so they are encrypted or check transactions
3. that multiple different inputs don’t create the same output

[AndreuStein]

1. Functions in which each unique input creates a unique output, and the input cannot be found from knowing the output.

2. Hash functions are used in cryptocurrencies to create public and private keys, confirm transaction data, and create blocks.

3. Collision resistance refers to the highly unlikely chance that two inputs can ever give the same output in a hash function.

[ccbit]

1. One way functions that are practically impossible to go from a given output to a it’s input.
2. It’s used in mining for unconfirmed transactions. Something about changing a signature until a has produces a number of 0’s.
3. It’s mathematically difficult to have 2 inputs give the same output.

[Jordan_James]

1: Hash functions allow for computations to be carried out on an input, in such a way that the input cannot be derived from the output.

2: The hash of the previous block is included in the current block, creating an unbroken chain that is impossible to wholly reproduce in the time it takes to mine a block.

3: Collisions in hashing refers to two different inputs having the same output, resistant to this refers to when it is hard to do so.

[Jose_Hernandez]

1. Hash functions are functions which produce an output from a certain input and ideally the input cannot be determined from the output

2. Hash functions are used in public and private key cryptography and in the proof of work part of a block

3. It means that no 2 inputs can produce the same output

[samjlunt]

1. Describe hash functions with your own words
   Hash functions take data and covert it into a specified output using the desired hash code. Bitcoin uses SHA-256 which means it converts the data into 256 bits. This creates a random code that cannot be reversed or changed and is essentially a digital fingerprint.

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 used in Bitcoin by taking a transaction amount (ie 0.5 btc) and converting it to SHA-256 so that it can be transacted on the Bitcoin network. This will create a digital fingerprint for the specific transaction and that will be held in the ledge. Anyone can view this hash but it cannot be changed, deleted or hacked.

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 resistant means that the hash function is cryptographically secure. Using SHA-256 means that it is hard to find two inputs that has to the same output, so hard that it is mathematically impossible to do with the human brain or current computer capability in 2021.

[jornack]

1. Describe hash functions with your own words
   A Hash function is a one-way function takes a value, performs some calculations with it and outputs a unique string.

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 function are used to write new transaction into the blockchain through mining.

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 function is collision resistant when it’s hard or impossible to find two input values that produce the same output.

[Dfogleman03]

1. a hash function is a linear equation used to translate an input into a unique output.

2. hash functions are used to mine blocks, encrypt individual transactions ( kind of like a receipt), and secure the Bitcoin protocol.

3. collision resistance in blockchain means the difficulty in trying to re-create an output from a particular hash function.

[jude]

1. Describe hash functions with your own words:
   Hash Functions are functions that take a unique input and produces a unique output, in a process that is not reversible. This means there is no way to figure out the input basing only on the output.

2. How are hash functions used in cryptocurrencies like bitcoin?
   They are used to “summarize” a block of transactions, and then used as a header for the next block. Thus, the hash is the link the chains one block to another.

3. What does it mean when we say that hash functions need to be collision resistant?
   To be “collision resistant” means, there has to be 1:1 correspondence between the input and output. If 2 or more inputs create the same output, then that is called a collision.