Reading assignment: Hashing

[MusicforMovies]

Good question in regard to the Hash Pointer; I was wondering that myself.

<<Instead of going through the cumbersome process of looking at each individual hash and seeing whether it belongs to the data or not, I can simply track it down by following the trail of hashes leading up to the data:>>

Maybe the above process of “following the trail of hashing leading up to the data” i.e. going backwards on the chain has some particular effect that isn’t covered yet.

[sahowe1]

1. What is the hashing algorithm called used in Bitcoin?

SHA256

Something Hashing algorithm

2. Why is this hashing algorithm really hard (almost impossible) to brute-force?

As the length of the string being hashed increases in size it become exponentially difficult to guess (without a quantum computer)

[SoyBoy]

1. What is the hashing algorithm called used in Bitcoin?
a. It is called SHA-256 (Secure Hashing Algorithm)
2. Why is this hashing algorithm really hard (almost impossible) to brute-force?
a. Because SHA-256 is pre-image and collision-resistant, with the length of the hash currently long enough for SHA to be secure

[bithomie]

1. SHA256
2. Because of the design of cryptographic hash function, a random guess (nonce), has to concatenate with the hash of the block and be less then the known difficulty to solve the puzzle.

[IZUMI]

1. SHA-256
2. It is hard to brute-force, firstly because the process of solving the hashing algorithm is done entirely by random. In order for a miner to brute-force the algorithm, they need to take the hash of the block, concatenate it with the nonce, an arbitrary string of values, hash it again. They Keep repeatIng the process with a new nonce each time until the results are Good to be accepted.

Secondly, there is a specified hash rate for each block to be mined to maintain a specific and predictable supply of Bitcoin. The competition would be increased by the number of active miners participating to generate new blocks.

[IZUMI]

Hi
Can you explain me the age of the universe?
In a simple way as I have no clue of this.

Thank you

Izumi

[Mauro]

@MarcisB

Block 3 contains hash of block 2, not vice versa. Why would block 2 change? I think it should say block 4, which in turn would change block 5, and so on, in the other direction.

@MarcisB @MusicforMovies

I think the article says block 3 for a block that is 3 blocks old. When you modify something in a block, the hash changes and all blocks newer from that point one will be invalid. It will cause a chain reactions of hashes being changed.

[Mauro]

@Changfa_Lin

you need to try 2^127 times to resolve it

I think its 2ˇ255. Either way its way to big. There is around 10^80 atoms in the universe. With the current speed of computers, we would never be able to brute force a single hash.

[Mauro]

@welowy

Because the nounce must be changed many times until the requirements are met.

@bithomie

2. Because of the design of cryptographic hash function, a random guess (nonce), has to concatenate with the hash of the block and be less then the known difficulty to solve the puzzle.

@IZUMI

2. It is hard to brute-force, firstly because the process of solving the hashing algorithm is done entirely by random. In order for a miner to brute-force the algorithm, they need to take the hash of the block, concatenate it with the nonce, an arbitrary string of values, hash it again. They Keep repeatIng the process with a new nonce each time until the results are Good to be accepted.

Brute forcing the Sha-256 algorithm in itself is what we meant by the question. We wanted to makes sure that you understand that the miners need to put the work in order to mine a block. There is no shortcut for a miner to solve a block. The Sha-25 algorithm is impossible to brute force with the current technology due to how many possibilities it has. 2ˇ256

[BullRunner]

1 The hashing algorithm used in Bitcoin is called SHA-256
2 While a 256 bit encryption is hard to brute-force, it would generally take so long that it doesn’t matter. It is a mathematical possibility so remote that it is practically impossible. Not only being a time lengthy process, but tampering with encryption would affect the rest of the previous blockchain data set and eventually be prevented and null.

[Mauro]

@coin_digger

When we say brute-force we mean that a computer is systemically looking for a hash collision by trying every possible combination until it encounters one.

Finding a collision in a hashing algorithm is a vulnerability. MD5 hash has such vulnerability. However as far as I understand it is still hard to guess the input from a given hash, even in MD5 hash. When we say brute-force, we mean finding an input based on an already given output. If you can achieve this you essentially broke its whole purpose of being secure.

Is MD5 considered insecure?

“The attacks against MD5 are collision attacks, not pre-image attacks. This means an attacker can produce two files with the same hash, if he has control over both of them. But he can’t match the hash of an existing file he didn’t influence.”

[Mauro]

@Douma

2. Because it is literally impossible to find input out of outputs, it can be done but it is based on a pure luck.

Its a lottery, you will never win.

[Mauro]

@Fati

Because there are so many possibilities that it would take lifetimes to figure out.

It would take you 3.6 x 10^13 years. And this is for collisions, finding an input based on an output would take even longer.

Why haven't any SHA-256 collisions been found yet?

[Mauro]

@Edu_H79

2. Why is this hashing algorithm really hard (almost impossible) to brute-force?
Brute force may in fact be successful; however the chances of success are so astronomical that it is not worth the time and effort.

Simply put, 3.6 x 10^13 years so when compared to the age of our universe 13.7 x 10^9 years old… Well… Good (you’ll need a lot more than than just “good”) luck with that, bub! ).

Yep. Brute force needs to be consistent, guessing once won’t get us far. Great job on googling and finding more information about Sha-256.

[Mauro]

@dbell101

The chances of randomly guessing the input values is so high and would take so long that it doesn’t matter.

I assume you meant to say that the chances are very low.

[Mauro]

@successfs

2- It is difficult to find 2 input who have the same output on a hash function.

@Kat1

2. each input has a unique hash; infeasible to find two inputs that hash to the same point

Finding a collision is hard, as well as finding an input based on a given output. By brute force, we mean finding an input from a hash.

[Mauro]

Awesome answers. I see you also searched us more about the SHA-256 on the internet. Keep it up!

@scornkrypto

Hashing is a one way function – it cannot be decrypted back.

It would be more appropriate to say dehashing. But then again, if there is a way to dehash, then its not a hash function. Hash function must be one-way, finding a way back breaks their purpose. Encrytion and hashing are 2 different things. Encryption is meant for an eventual decryption with a proper key.

Why salted hash is as good for passwords as for breakfast -- GCN

“Encryption is a two-way function; what is encrypted can be decrypted with the proper key. Hashing, however, is a one-way function that scrambles plain text to produce a unique message digest. With a properly designed algorithm, there is no way to reverse the hashing process to reveal the original password.”

[Mauro]

@IZUMI

Secondly, there is a specified hash rate for each block to be mined to maintain a specific and predictable supply of Bitcoin. The competition would be increased by the number of active miners participating to generate new blocks.

What do you mean by specific hash rate? Every 2016 block, the bitcoin network adjusts the mining difficulty. This ensures that the miners find a block every 10 minutes or so. This does not predict the supply of bitcoin but rather the new supply, also know as inflation. Maybe you already knew all of this, but I was just a little confused about how your wrote your answer. Hope this helped.

[Mauro]

@IZUMI

Can you explain me the age of the universe?

I don’t think there is much to explain. We assume that the universe is that much old. We can all assume that the universe is very old in general. The given example, is there to give us perspective on the time it would take to brute force Sha.256. Keep up the good work, and always stay curious.

[Mauro]

@BullRunner

but tampering with encryption would affect the rest

Great answers. However, there is not encryption in hashing. Encryption is a two way function, while hashing is a one-way function. Don’t worry too much about it, but if you are interested in the difference here is a good read:

Difference Between Hashing and Encryption