Homework on Hash Functions - Questions

Blockchain and Bitcoin 101
#3518

  1. Hash functions are one-way, unidirectional functions in which the raw input data is translated into a cryptographic alphanumerical string, or an output called hash.

  2. Hash functions in bitcoin are used for the creation of the new blocks, which are added to the chain (blockchain) every 10 minutes, and which contain hashes of the transactions on the block. In order for a new block to be created every 10 minutes, miners have to hash six inputs of the previous blockheader (1. software version when the block was created, 2. timestamp on the block, 3. hash of the of header of previous block, 4. Merkle root (a root signature of all the transactions on the block), 5. Difficulty target, 6. nonce) and get the number that is smaller than the difficulty target. Whoever solves the equation first, gets rewarded with 6.75 btc, which is a reward per block.

  3. It means that the probability of distincting two separate inputs producing the same hash should be close to impossible.

1 Like
#3519

  1. A hash function turns digital information into a unique fingerprint of digits and letters. If information gets changed just slightly the output (hash) changes completely.

  2. In order to be able to do any kind of transaction you need a hash.

  3. Collision resistant means it is nearly impossible to generate the same hash with different inputs.

1 Like
#3520

1 Itā€™s a math algo, created from an input to a one way output, with no possibility (with the actually state of computing technology) to entropizing it.

2 Btc hashes are created from high rate calculator, transforming transactions in unique identification codes (publics and privates keys have nothings to do).

3 A Collision resistance, is the aptitude of a hash function to produce, generate, by two different input, always a different output.

1 Like
#3521

Private keys are just random numbers and public keys are derived using the Elliptic curve function, not SHA256. :slight_smile:

#3522

Ok, Iā€™m going to find out more about Elliptic curve function, :grimacing:
Thanks

#3523
  1. Itā€™s a function which converts any alphanumerical string into a a unique combination of letters and numbers.
  2. It is used to write new transactions into the blockchain through the mining process.
  3. It means that thereā€™s only one output for a certain alphanumerical string. A single change in the string will completely change the complete hash. In other words, thereā€™s no way a hash can be repeated by two different alphanumerical strings.
1 Like
#3524

  1. Describe hash functions with your own words
    A has function is a data with an arbitrary size to fixed- size values. The values returned by a hash function are called digits.

  2. How are hash functions used in cryptocurrencies like bitcoin? Bitcoin uses hash function by using Secure Algorithm (SHA256). This has an input string of any length and giving out an output with fixed length. The unique output canā€™t be reverse to the original input.

  3. What does it mean when we say that hash functions need to be collision resistant?

Each input will have a unique hash. Having two different input that result in the same has is known as ā€œcollision resistant.ā€ No has function is completely collision free.

1 Like
#3525 
   1. Describe hash functions with your own words

A hash function is a functions that delivers a unique output for each unique input provided. Because of this fingerprint system-like, it is impossible to figure out what the input number is based on the output result. It is a one way function.

   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 and other cryptocurrecies as the fingerprint of each product available, and in that case, of each single token. Each btcoin for example, is the result of a hash fuction wich provides itā€™s unqueness, itā€™s traceability and itā€™s autheticity.

   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 is a way of writing the function to make it harders for attackers to figure out the input given. It becomes impossible to search for similar signatures in hash functions.

1 Like
#3526

  1. Hush functions are complicated algorithms which transforms data input to a unique cryptographic output. The process is irreversible and cannot be trailed back to the original source.

  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. Collision resistance in a hash function means that there is a very low probability that any two random inputs can generate the same hash output.

1 Like
#3527

  1. There are many different kind of hash functions. They all take any desired input, such as the number of btc being sent p2p, and then plug that input into a function that produces a unique hash, or output. If any minute change is made to the input, it produces a completely different hash.

  2. PoW is the consensus mechanism of the Bitcoin blockchain, which takes the information from the transaction such as amount of BTC, previous block hash, and the time of the transaction and plugs it into the SHA - 256 hash function to get a unique hash. After multiple nodes confirm their hash comes to consensus with the other nodeā€™s hashes, the transaction is verified and a new block is added to the blockchain.

  3. When you say that a hash function needs to be collision resistant, you mean that it is extremely difficult to find 2 different inputs that create the same output. H(a) cannot produce the same output as H(b).

1 Like
#3528

  1. Hash Functions are on way functions where each unique input produces a unique output or digital fingerprint.

  2. Hash Functions are used in crypto like BTC to hash transaction data and in mining to find the hash required for each block.

  3. Collision resistant means that hash functions cannot share two unique inputs that produce the same output. Itā€™s virtually impossible but not plausible considering its difficulty.

1 Like
#3529

  1. Hash functions are one one way encryption function. The hash value is the fingerprint. There is no now way to decrypt the hash back to its original value.

  2. In Bitcoin the whole block and the transactions in it are hashed with SHA256. So every block contains a hash value as an id and a hash value of the previous block. With these hash values, all blocks in the blockchain are connected.

  3. It means that every input data has its own hash value, so it is unique. There is no way that two different input values produce two identical hash values.

1 Like
#3530

1, A hash function is a digital footprint where a given input is entered it will give a unique output.
2, Bitcoin transactions are hashed using SHA-256, when each new block is created it is hashed to the old block using the previous function output
3, Outputs of each unique input will be different

2 Likes
#3531

  1. A Hash function takes a unique input and produces a unique output -creating a digital fingerprint. A Hashing Algorithm is considered secure when it is impossible to take the output and reverse it

  2. Bitcoin is simply a digital ledger of hashes that utilizes proof of work combined with SHA 256 to obtain mathematical unbreakability and traceability . The process that utilizes Bitcoin Hashes is called Mining

  3. A Hash function is collision resistant if it is hard to find two inputs that hash to the same output

2 Likes
#3532

  1. Describe hash functions with your own words

  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).

  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).

  4. Its an one way function . You can go from input to output , but you can never output to input. When we give an input in a hash function as an output we get a digital finger print .

  5. 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.

  6. Collision resistant means two different inputs should not give the same output hash.

1 Like
#3533

Describe hash functions with your own words:

Hash functions encrypt data input into a digital ā€œfingerprintā€ that can not go backwards from the output to the input.

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).

All of the information from a transfer of bitcoin is hashed and then added into the blockchain. It is checked and the hash is verifiable by all nodes on the network. It is hashed to keep all information anonymous and untraceable.

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 there can not be two hash outputs that are the same, as all the inputs will be different.

1 Like
#3534

  1. Hash functions are advanced sets of mathematical computations that are unidirectional. Not possible to get the input based on a given output. We know the outputs once completed and we know the method used to get the output but the input is secure.

  2. Hash functions are used to protect the integrity of distributed ledger.

  3. Collision resistance means its very unlikely two inputs will give the same output

1 Like
#3535

  1. A hash algorithm is a universal translator for computers that receives data in any shape and form. Each unique input gives a unique output. You can go to input to output but you canā€™t go to output - 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. 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 H is collision-resistant if it is hard to find two inputs that hash to the same output; that is, two inputs a and b where a ā‰  b but H(a) = H(b). Any hash function with more inputs than outputs will necessarily have such collisions the harder they are to find, the more cryptographically secure the hash function is.

1 Like
#3536

Answers to the questions:

  1. Based on some input it will generate an unique output value for that particular input value. From the hashed value it is not possible to get the original value, unless using an unsecured hashing algorithm (md5),
  1. When finding a block it will be added to the blockchain.

3 That itā€™s hard to get the same output hash with different input values.

1 Like
#3537
  1. Describe hash functions with your own words

They are input functions that will generate a unique digital fingerprint, which can not be translated back into the input from the output

  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).

Itā€™s used to signify proof of work. one Miner can mine A transaction, then they hash it to the blockchain, and can then be verified,

  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).

When its is hard to find two inputs that hash to the same output.

1 Like