Reading assignment: Hashing

Blockchain and Bitcoin 101
#866

Thanks for that concept. i just looked at it as a big guessing game of mathematical equations to solve and get the random nonce # to receive the incentive fee’s.

#867

Can you explain why that makes it hard?

#868
  1. SHA-256
  2. Because when randomly guessing a hash that is the size of SHA-256, the amount of guesses needed will grow expnentially and it would theoretically take many lifetimes to guess it (brute-force).
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#869
  1. Sha - 256

2.Its hard because there are so many millions of different combinations to guess.

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#870

  1. What is the hashing algorithm called used in Bitcoin?
    SHA-256

  2. Why is this hashing algorithm really hard (almost impossible) to brute-force?
    The SHA-256 hashing algorithm produces a hash which is a random 64 character string of letters and numbers. In order to determine the input which produced the hash, the only method is to randomly guess and compare the output, but there are 2^256 possible outputs so finding this takes an enormous number of guesses; this translates to computing power as the higher the computing power, the more guesses can occur within a certain time frame.

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#871

  1. SHA-256

  2. because it has very low probability of gessing input value from the resulted hash (high pre-image resistance) … it would in average take 2^255 attempts to hash and compare for the attacker

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#872
  1. What is the hashing algorithm called used in Bitcoin?

Secure Hashing Algorith 256

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

The number of computational possibilities is so high with a 256 hash that it would take too long to bruteforce it.

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#873

The hashing algorithm that is used for Bitcoin is called SHA-256.
SHA(Secure Hashing Algorithm), and it is 256 bits in length

Some of the reasons the hashing algorithm is almost impossible to brute force are as follows

  • The high min-entropy of the nonce, which is in the distribution of 1…10^24
    • This nonce is a randomly generated string value that is generated from a extremely large distribution. This arbitrary string(nonce) must then be concatenated with the hash of the block, and the result must be less than the difficulty target
    • This requires a massive amount of computing power, which makes it infeasible
    • If someone hacks into a block and makes a small change to the input, the all the previous blocks will be notified of this change, and it will be rejected
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#874
  1. What is the hashing algorithm called used in Bitcoin?
    Answer: SHA-256
  2. Why is this hashing algorithm really hard (almost impossible) to brute-force?
    Answer: The output is 256 bits long - 2^256 combinations possible . While it is possible to break pre-image resistance via the brute force method, it takes so long that it doesn’t matter.
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#875
  1. What is the hashing algorithm called used in Bitcoin?

SHA-256

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

Odds are that even the average length of time to guess the right input to match the hash would take several lifetimes.

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#876
  1. What is the hashing algorithm called used in Bitcoin?

Secure Hashing Algorithm 256 (SHA-256)

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

An attacker might be interested in ‘rehashing’ a block of transaction data so it can be modified (adding a fraudulent transaction or undoing a payment) and then submitted back to the blockchain. To do this they would have to brute force attack the SHA-256 algorithm which means executing it many times on guesses of what the data could be, to eventually find a matching hash confirming the data. This isn’t impossible but is considered infeasible because of the vast computational power it would require. In addition to this, every subsequent block in the blockchain would need to be re-hashed to hide the modification as they each contain a hash of the previous block.

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#877
  1. SHA-256
  2. Finding the input based on the output is like finding a special grain of sand at a beach, almost impossible.
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#878
  1. What is the hashing algorithm called used in Bitcoin?
    SHA-256 is the hashing algorithm used in BTC.
  2. Why is this hashing algorithm really hard (almost impossible) to brute-force?
    because the chances of you getting the same input is practically impossible.
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#879

  1. SHA-256

  2. Because the time it would take makes it infeasible to brute force.

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#880

  1. What is the hashing algorithm called used in Bitcoin?
    Sha 256

  2. Why is this hashing algorithm really hard (almost impossible) to brute-force?
    Because the possibilities of 2 people getting the same results are to small thanks to the 256 hash. The SHA 256 have 2^256 different possibilities in form av 78 digit number.

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#881

Answer the questions below.

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

it’s called SHA-256 (or in post-revolutionary Iran it’s called Ayatalloh-256)

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

Because using brute-force you have to pick up a random input, hash it and then compare the output with the target hash and repeat until you find a match. Randomly comparing the hashes for the huge number of inputs that are on a blockchain just takes a huge amount of time - and we just don’t have that amount of time to waste on trying to match outputs. Have a coffee instead, naturally no milk, no sugar involved :wink:

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#882
  1. sha256
  2. It takes so long to do that, that in the end it’s not worth it
1 Like
#883

secure hashing algorhithm 256 SHA 256
because the number of permutations of possible outcomes is so high that it would take too long to find a collision

#884

  1. SHA-256

  2. While it is possible to break pre-image resistance via the brute force method, it takes so long that it doesn’t matter as it will not happen.

1 Like
#885

  1. What is the hashing algorithm called used in Bitcoin?
    SHA-256 (Secure Hashing Algorithm 256)

  2. Why is this hashing algorithm really hard (almost impossible) to brute-force?
    The possibility of picking a random input, hashing it, and then having that match the output of the targeted hash is “astronomically” low. So, although not impossible to brute force, almost impossible. It would also take an incredibly long time to test multiple inputs because of the quantity & type of characters used. One small change to any character will produce a completely different output.

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