Reading assignment: Hashing

Blockchain and Bitcoin 101
#2171

  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?
    It’s infeasible not impossible because there are so much probabilities to find the output and takes so long time and energy

1 Like
#2172

the only way to find the input is by keep guessing the input and compare the hash. It’s like guessing every combination of a pin-number. For a 4 digit pin-number you have 10000 possibilities.
in sha256, you have 2^256 possibilities + the chance of a collision.

2 Likes
#2173
  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 it takes so long that it doesn’t matter.
1 Like
#2174

  1. sha 256

  2. becasue youll be guessing the input for a lifetime

1 Like
#2175

  1. SHA-256

  2. The amount of data it too large

1 Like
#2176
  1. What is the hashing algorithm called used in Bitcoin?

Secure Hashing Algorithm SHA-256

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

It is not feasible as it takes too long to break pre-image resistance.

1 Like
#2177
  1. Secure Hashing Algorithm 256 (SHA-256)
  2. This hashing algorithm is almost impossible to brute force because the range of possible answers is so vast and the algorithm is based off randomness, so matching a hash by accident is not likely.
1 Like
#2178

  1. SHA-256

  2. Because of the vast amount of data in that blockchain (2^256-1) and pre-image resistance (the hash itself). Anyone trying to brute-force would have to go through a serious amount of inputs before even finding target hash unless they’re extremly lucky.

1 Like
#2179

Q1: What is the hashing algorithm called used in Bitcoin?

A1: SHA-256 (Secure Hashing Algorithm 256)

Q2: Why is this hashing algorithm really hard (almost impossible) to brute-force?

A2: Statistically - with an average scenario - it would take too long to achieve

1 Like
#2180
  1. SHA-256
  2. It hard to brute force because of you have to take a random input, hash it and compare it with the output, this will take a very long time because of the larger entropy used.
1 Like
#2181

  1. SHA-256

  2. By Brute-force method we are basically talking about taking a random inputs and hashing it and comparing the output hash with the target hash. However, in the Blockchain, The Inputs in the formula H(k|x) = Y are Nonce (K ; Which is random) and X (The hash of the block) and these inputs are hashed and compared against the Difficulty Target (Y) which increases with every 2016th block created. So this randomization of Nonce and the Difficulty Target changing makes it more difficult to Brute-force.

1 Like
#2182

You mean the hash of the previous block? :slight_smile:

Not necessarily, difficulty might also decrease if the hash power of the network drops.

2 Likes
#2183
  1. SHA 256
  2. Brute forcing is infeasible due to hashing being a combination of puzzle friendly, pre-image resistant and collision resistant.
1 Like
#2184
  1. SHA-256.
  2. Because it is pre image resistant, which means that is almost impossible to determine the original input only with the hash value.
1 Like
#2185

  1. The hashing algorithm used in bitcoin is called SHA-256.

  2. This algorithm is almost impossible to brute force because it would take multiple life times to guess.

1 Like
#2186

Hashing :hash:

  1. What is the hashing algorithm called used in Bitcoin? :lock_with_ink_pen:
    Bitcoin uses SHA-256 which is a version of the Secure Hashing Algorithms that produces hashes of fixed length (i.e. 64 hexadecimal digits [0-9a-f] representing 4 bits of information each that consequently contain 256 bits of information all together).
  2. Why is this hashing algorithm really hard (almost impossible) to brute-force? :muscle:
    In order to brute force such a hash an attacker must try on average half of the possible combinations. Making small computations 2^255 times on average will take many many lifetimes regardless of how much processor speed might increase in the future.
    SHA-256 might be broken (not brute forced) within the next century, however, if someone comes up with a smart algorithm that reduces the number of necessary tries significantly.
1 Like
Is there a limit to chain of hashes?
#2187
  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?

Because to guess the correct hash and the nonce together is mathematically improbable even in multiple lifetimes. It requires an inordinate amount of computing power.

#2188

  1. What is the hashing algorithm called used in Bitcoin?
    It is called SHA256

  2. Why is this hashing algorithm really hard (almost impossible) to brute-force?
    This is because of a property of Hashing called “Pre-Image Resistance”. Hashing is the process of giving a string of text of any length a fixed output value. Hashing is deterministic in the sense that no matter how the input is parsed the out output is the same. As a result we only need to keep track of the output. Now, we have a large number of input, if we pick a random input and hash it, we have to compare its output to the target hash output to find a match this makes it really hard to brute force because of the time it will take.

2 Likes
#2189

But in this question of Sha256, the nonce has nothing to do with it. A nonce is just to create a special block hash that is low enough to be accepted by the bitcoin network

#2190

  1. SHA-256

  2. Brute-forcing hash algorithms means trying repeatedly random inputs until finding the desired output. For SHA-256, there are 2^256 possible outputs. Worst case scenario this would result in 2^256-1 attempts before finding the solution, or in average 2^256/2=2^255 attempts. These are very huge numbers: it will take more than centuries to brute-force SHA-256…

1 Like