2.Hash functions are used in Bitcoin to keep it secure.
Hash functions are functions that have one unique output per unique input AND characterized by the property that an input of a hash function can not be determined by an output of a hash function.
I don’t completely understand yet, but I think POW tries to take some output to a hash function and brute force the original input. This is considered verification and the miner who verifies gets the new bitcoin rewards.
Collision resistant means it is difficult for two different inputs to a function to yield the same output. I am interested in learning more about this because in the lecture it was mentioned that input output pairs are unique, if the hash function is only ‘resistant’ to this behavior and not 100%, then I wonder what kind of issues that might cause.
Hash Functions is a mathematical function that converts any data of any length into a fixed size string of text. This mean that any data length can be converted into a fixed text of number and letters threw an algorithm. Each hash value or output has to be unique, this means there cant be same hash value
How are hash functions used in cryptocurrencies like bitcoin?
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.
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.
Collision resistance is a property of cryptographic hash functions: a hash function is collision resistant if it is hard to find two inputs that hash to the same output.
Hash functions take an input of any size and create a unique output of a fixed size. If you have the same input it will always generate the same output. That being said it is in feasible to go from output back to the input.
Hash functions are a core part of how crypto currencies work. The transactions are taken as inputs and put through a hashing algorithm (SHA-256 in Bitcoin) then into a block in a linked list. This block will also contain the Hash of the previous block. This is what gives blockchain its immutability, changing one tiny piece of one block will change all of the rest of the blocks in the chain.
Collision Resistant basically just means the chance of 2 separate inputs creating the same hashed output is infeasible. It is not impossible but the likelihood of it happening would take so long it wouldn’t matter.
Its extremely unlikely to find a collision in SHA256 but there have been other hashing algorithms that have been cracked in the past like MD5 (https://natmchugh.blogspot.com/2014/11/three-way-md5-collision.html)
2)Hashed data, is compressed, so it is easier to store, manipulate and track. With Bitcoin, all transactions are hashed.
Also for security reasons, as hashed data can not be recovered. So for public and private keys fe.
Describe hash functions with your own words
Is a one-way function that allows a unique input to produce a unique output that cannot be reversed engineered?
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).
In cryptocurrencies we wish to be able to eliminate the possibility of reversing a hash (Unique Output) to its original Unique Input data. This is a must for a cryptocurrency to exist. That is why we use SHA – 256 in the creation of Bitcoin which has high collision resistance. This maintains the one way requirement of Hash creation and eliminates the possibility of reverse engineering the output in to the Input data.
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 resistance is a property of cryptographic hash functions: The hash Property is to minimize (Bring to 0) the option of unique inputs that hash to the same output. a ≠ b but f ( a ) = f( 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. Example SHA – 256 which is used in Bitcoin.
Homework on Hash Functions - Questions
If someone figure out how to produce the input from the output it means that the hash function has ben broken and it cannot be considered a hash function anymore.
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).
The hash function used in Bitcoin is double SHA-256, basically there is a target value that is a number adjusted every 2016 blocks and it can be increased or decreased depending how faster is the mining process. This target is effectively the same for all nodes because all nodes adopt the longest chain of block as their blockchain. In order to mine a block, so add it to the Bitcoin blockchain and so validate transactions, all computers in the network hash the previous block informations such as previous block hash, timestamp, bits, nonce etc. until the result, that is a hash, is a number lower than the target. Usually is very hard to find such a number, like in a lottery, and miner change the nonce value or other block contents and tries again until someone find a hash that is less than the target. Only the first in the network that “win the lottery” will be rewarded and the block that it had hashed will be part of the Bitcoin blockchain.
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 collision means that two or more inputs generate the same output. This shouldn’t happen to a hash function or the definition of hash function is not respected and it becomes vulnerabile.
Hash function is basically a mathematical function used in cryptography and which take inputs of variable lengths to return outputs of a fixed length.
In cryptocurrencies like bitcoin, hash functions are part of the block hashing algorithm which is used to write new transactions into the blockchain through the mining process.
Well, it simply means that the hash function has unique input values ( hard to find) of two variables i.e a and b but the hash output of both variables is similar. Then it will be collision resistant however if the input values that hash to the same output are known then it wont be collision resistant.
[quote=“ivan, post:1, topic:8430, full:true”]
Homework on Hash Functions - Questions
Hash functions are functions that , when ran with a hashing algorithm, will have an output from which you can not guess the input.
They are used to create the public and private keys.
A hash function is collision resistant if it is hard to find two inputs that hash to the same output
1.hash functions are a one way input to output digital fingerprint
2.in bitcoin the hash function is to Hash transaction data, typical hash functions take inputs of variable lengths to return outputs of a unique fixed length
3.when a collision happens it means that you suddenly have two different Inputs with the same hashed output , this makes it incompatible
Describe hash functions with your own words
A hash function generates a unique fixed 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).
Used by the Bitcoin network to generate the public & private keys, addresses, and are used in the mining verification process.
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 it is impossible for a hash function with two or more different inputs resulting in the same output.
A hash function is a uni-directional function that takes a given input and runs it through a cryptographic formula, giving an output that can serve as a fingerprint of authenticity for the input. Given the input, hash function, and hash, you could run the input through the hash function and compare the new hash to the prior hash to see if they are identical or not. If not identical, there has been a change to the input.
Hash functions has multiple uses in blockchains: A) Each block header gets hashed to create a block hash, a unique identifier for each block, which also gets included in the block header of the next block, creating a chain of blocks, ie. blockchain. B) Each transaction gets hashed to create a transaction hash, giving the transaction a unique identifier. C) A public key gets hashed to create an address.
Collision resistance has to do with how likely two inputs are to come to the same hash when run through the same hash function. Common collisions would negate the value of hash as a unique identifier for verifying message fidelity.
1. Describe hash functions with your own words
Hash functions seem to be the ‘secret sauce’ of Bitcoin. It is the resulting output that uses SHA-256, a Base-16 system comprised of 0-9 and a-f.
2. How are hash functions used in cryptocurrencies like bitcoin?
With the risk of sounding foolish, I’ll give it a go! The input of the hashes of every transaction are recorded on a block. That block gives an output using SHA-256. Miners jobs are to use their computing power to find a portion of the hash that is in the nonce. Once that is achieved, the block is verified and added to the chain.
3. What does it mean when we say that hash functions need to be collision resistant?
A hash function is collision resistant if it is hard to find two inputs that result in the same output. From what I understand, if hash functions were not collision resistant, it would open the door to possible attackers using a replica input to cheat or be dishonest.