Reading assignment: Hashing

Blockchain and Bitcoin 101
#1387
  1. The hashing algorithm used in Bitcoin is called SHA-256.
  2. The SHA-256 algoritm is infeasible to brute-force because it has 2^256 different probabilities. In a normal scenario it will take so long time to brute-force this that it becomes infeasible.
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#1388

  1. SHA-256

  2. Brute-force is like guessing. It would take so long that it is not worth the time.

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#1389

SHA -256
The current computing capacity make the brute force method unrealistic as the numbers of possibilities is too large

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#1390

  1. BTC’s hashing algorithm is SHA256.

  2. It is almost impossible to brute-force due to nonces of high min-entropy concatenating with the block’s hash. This arbitrary string of values (nonces) increase the difficulty level by adding randomness into the mining process.

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#1391

Nonce does not increase the difficulty :slight_smile: it is basically just a number the miners use to help themselves with finding the correct answer to the cryptographic puzzle :slight_smile:

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#1392

1.) SHA-256

2.) it takes so long that it doesn’t matter.

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#1393
  1. SHA 256
  2. It will take too long at least with the current processors available; what will happen when quantum computing will become mainstream?
#1394

Quantum computers at the current state are specialized for a specific task and are still not good enough to break the encryption. If one day a quantum computer does manage to break SHA256, a fork will be required to migrate to a new algorithm that is quantum resistant :slight_smile:

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#1395
  1. What is the hashing algorithm called used in Bitcoin?

SHA 256 (Secure Hashing Algorithm 256)

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

A slight change in the input would cause a big change in the hash outcome. As the blockchain is a linked list of ledger entries, each change to a block would require to change the foregoing blocks, as well. That is why it would require infeasible computing power to apply all the necessary changes to alter a ledger entry. Incentives are set in such a way that it is more rewarding to use this computing power otherwise, for example verifying legitimate transactions.

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#1396
  1. SHA-256 generates a number in binary format transformed to HEX-format.
  2. The property of “very large numbers”. As the Hash is a non invertible function: If H(x)=y the inversion G(y)=x is extremely hard to find.
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#1397
  1. Sha256
  2. There are too many possibilities, so its unlikely to guess in a lifetime.
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#1398

The hashing algorithm is called SHA-256.

The hashing algorithm is almost impossible to brute force attack because it has a combination of 2^128 which is an extremely high number. It would take several years to find the original output by 2^127 attempts.

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#1399

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

  2. Why is this hashing algorithm really hard (almost impossible) to brute-force?
    Because by brute forcing which means picking up a random input, hash it and then compare the output with the target hash and repeat until you find a match would take so much time that it doesn’t even matter.

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#1400

Your explanation is correct. However, the question was more related to the hash function itself. Why can’t we just simply try all combinations to get the input from the output?

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#1401
  • What is the hashing algorithm called used in Bitcoin?
    SHA256
  • Why is this hashing algorithm really hard (almost impossible) to brute-force?
    Because of the components and amount of time that is required to guess (brute force) the hashes.
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#1402

Yip, not only do we all put 100% trust in the bitcoin development team but we trust that IBMs super computers can’t crack the hash. As if our antminers or graphics cards can compare to these clustered computational powers. Just a heads up for those who can see the one world controlled currency on the way. Still a fan of monero and gold of course :wink:

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#1403

@Alko89 Thanks for the note! To make sure I understand, the difficulty level is set without any correlation to the nonce?

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#1404
  1. SHA256
  2. If the data input gets changed in any way, a completely different hash is created
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#1405

  1. SHA256

  2. In order to find a hash collision you need roughly sqrt(2^256) = 2^128 items for 50% probability of some pair having the same hash. 2^128 = 10^38.5 is a very large number. If it takes 1 nanosecond to compute a hash, then it would take 10^22 years to compute 2^128 hashes. Also the memory to store these would also need too large a volume.

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#1406
  1. SHA-256
  2. Using an SHA-256 the whole system has a strong Pre-image resistance. Means that gives H(x) = Y is really unfeasible to find the value of X knowing Y, and this is thanks to a cryptographic function that change even for small variation of X. In the average case one that want to brute-force the system should randomly choose around 2^256 and find the correct value at 2^255, that is however a huge number of attempt.
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