Homework on Hash Functions - Questions

[Fabrice]

@wynand

The has function outputs a fixed length number (fingerprint) that can be referenced in the chain to validate (the previous block? next block?). It also protects against using the hash output to discover the input.

Yes every block contains the hash of the previous block.
So these blocks are cryptographical connected. If you would change information in a previous block, the hash would be completely different and break the link

[merlod911]

Q 1) Hash function are an essential part of digital information security. Hash algorithms include MD5 (message digest 5) its predecessor MD4, SHA 256 (secure Hash algorithm) one of its predecessor is SH 1, these are the cornerstone of e-commerce security. Hash function take input of any of nonspecific length then apply mathematical transformation to produce a stand length output called digest, tag or hash.

[merlod911]

Q 2) Hash function are the foundation of cryptocurrencies are they are the mathematics that generate secure private keys and address. The hash function is prerequisite in the development of bitcoin and other cryptocurrencies, it is also necessary for proof of work which is vital component in consensus. It is the inherent security in hash function that make bitcoin and other cryptocurrencies valuable.

[Gerard]

1. Hash Functions are a one way function that takes an input or string of any given data and the hash output is a unique fixed length digital fingerprint that can not be altered.

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). we’ve already seen that changing a small part of the input for a hash function results in a completely different output. This property is crucial to the ‘proof of work’ algorithm involved in mining: to successfully ‘solve’ a block.

3. Collision resistance is the property of a hash function that it is computationally infeasible to find two colliding inputs, it is this feature that makes hash functions so secure.

[merlod911]

Q 3) Note it says collision resistant not impossible this refers to two different input producing identical output hash’s while this has been done with MD -5. The bitcoin hash SHA-256 the number is so vast that it will take let say 100 year to produce identical output digest from to different inputs.

[1984]

@ivan

Homework on Hash Functions - Questions

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 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).

1. Hash function is a mysterious function that create a single output with a fixed number of digit from a given input. Very important is that it should not be feasible to find the antecedent from the result/the hash.
   2.hashfunction are used for multiple purpose:
   a. to allow easy verification of integrity as multiple/huge number of datas hashed will always give a single results when hashed. And the slighest change in the set of datas would give a completly different hash. Then all the datas of one blocks are summurized in a Hash, which is easy to verify.
2. A hash function must be collision resistant means that there should not be a chance that 2 different input give the same output

[Damedius]

1)A one way function where each unique input gives a unique output.

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)If a hash function is not collision-resistant then an adversary can break the function with little effort.

[ChrisK]

A hash function uses a secret key to turn an input into a secure private output.
Hash functions are used in cryptos like bitcoin to make the ledger impervious to hacking.
When hashes are collision resistant this means that there is little to no chance of any two outputs from different inputs being identical.

[Marco9]

1. Hash function is a mathematical process that takes input data of any size, perform an operation on it , and returns an output of a fixed size

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. In order for a transaction to be secure and be approved by consensus into the ledges it has to be collision resistant, it is unfeasible for two distinct transactions to have the same signature, though that it’s not impossible; in that case we can try to apply the brute-force method referring to the formula of the birthday paradox (I’m not entirely sure I’ve stated this part correctly, feel free to point it out there where you think i’m wrong )

[Alko89]

@Damedius

3)If a hash function is not collision-resistant then an adversary can break the function with little effort.

Collision resistance helps true, but it is in fact a property of hash functions that describe the probability of two inputs resulting in the same output.

[Alko89]

@Marco9

I’m not entirely sure I’ve stated this part correctly, feel free to point it out there where you think i’m wrong

It refers to different inputs, not only limited to transactions

[Mikos]

1. A hash function is such that a unique input will always produce the same output. In addition, it is impossible to determine what the input is using the output.

2. Hash functions are used in the process of inputing new transactions into the blockchain through mining.

3. “collision resistant” means that two different inputs cannot generate the same output

[dbtex35]

1. Describe hash functions with your own words

Hash functions create a unique output based on an input string of 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).

Hash functions are used to create hash pointers in a blockchain linked list. The hash pointer contains
the address of the previous block and also the hash of the data inside the previous block

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 if it is hard to find two inputs that do not hash to the same output

[gonzo]

1. A hash function is an algorithm that converts a key into a new value.
2. Hash functions are used for mining new transactions, public and private keys, and addresses.
3. Collision resistant means that each input generates a unique output. It is not impossible but highly unlikely for two inputs to generate the same output.

[AlexaE]

1. Processes that give you a unique digital fingerprint s an output, when you give an input.

2. Cryptography uses the capabilities of the hash functions to pass messages and to secure them.

3. It is impossible to find more than one input that matches a certain output, each input is unique and has it’s own output. Nothing else can match.

[Alko89]

@AlexaE

It is impossible to find more than one input that matches a certain output, each input is unique and has it’s own output. Nothing else can match.

It is possible, just highly improbable. In case it does happen its called a collision.

[CC123]

1. Hash functions are formulae that convert data into fixed length unique outputs.
2. All data is converted into sha 256 in the case of btc. The latest entry contains the new data including the hash of the previous entry. Sort of like a list of nested fingerprints.
3. There is a chance that 2 different inputs create the same output or hash, the chances of this is incredibly low, but still possible, collision resistance referes to how likely it is for this to happen.

[Vivek20]

1. A hash function is a function that creates a fingerprint of the input data that always gives the same fingerprint given the same input data and where it is infeasible / impossible to determine the input data from the output data.
2. Hashing is used in the addresses. The data is hashed and also it is used in mining.
3. It means that it should be very unlikely that to sets of input data generate the same output.

[Leighton]

1. A hash is a special function that takes a specific input and through computation creates an output, which will look encrypted but it closer to a unique digital signature.

2. These signatures are used to verify transaction data which are validated by miners on the blockchain which are stored on the ledger. The hash result will change completely with a smallest adjustment. Thus, generating the use of private & public keys in the use of cryptocurrency.

3. An important function of the hash is to prevent such an event from colliding on chain. Creating the term “collision resistant”. If a collusion would occur this would mean two different inputs that should not equal the same hash output, are presumed to be equal. This duplicate occurrence would create an unstable algorithm, but this is a highly unlikely probability.

[Lurkur]

1. Hash functions return a unique output for a unique input, which cannot be determined from the output.
2. Hash functions are used to securely record and verify transactions.
3. No two inputs should return the same output.