Ethereum Sign up or log in to customize your list._ Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top up vote 6 down vote favorite 1 When we look at this block - what does the first number Hash: 0xfe88c94d860f01a17f961bf4bdfb6e0c6cd10d3fda5cc861e805ca1240c58553 actually mean?How is it calculated?"Nonce" is the value that is changed during mining, but what is hash?blockchain hash block-header hash-algorithm ethash up vote 7 down vote The block header is the hash returned from generating a Merlkle tree that is below the current difficulty target for the blocks data.In order to understand what the block header is you need to understand what a hashing function is.A hashing function is a one way(non invertable function) that maps a set of inputs to a set of outputs hash(s) -> p, where for our purposes s and p are both strings.For any string s we can find the hash by applying our hashing function, which will return a new string.

This is a deterministic procedure in that given an s, the same hash() will produce the same p. There is no inverse of the hash operation, so you cannot go from output to input hash^-1(p) -> s.A hash function will ideally map the domain uniformly over the range such that any input that is in the domain will have a pretty even probability of being anywhere in the range vs more likely to be in a certain section.You use hashing operations for many different applications from data storage and lookup to logging into any password protected environments.It is also used to verify the integrity of data.Lets say you have a large file F. You can take the hash of the file by converting it to a string and then taking the hash of it, hash(F) -> G.G will be a string representation of (in this case) a 5 digit hexadecimal number(hashes like sha give you 40 digit hex numbers), lets say 0x5a3b1.Now some interesting properties can be examined.First is data integrity, if you wanted to download a copy of the file, you would need a verified copy already to compare with to ensure that it was the same one and not tampered with to go through and make sure every byte is the same.

With a hash we can do this much more easily.Since the hash of the original file always maps to the same G with the same hash function, the recipient can just take the hash of the file and compare it with a published hash of the file and see that they match.Changing even a single bit would change the value returned by the hash function.So whats a merkle tree?Blah blah, thats boring, what does any of this have to do with ethereum and blockchains?Well the data in the blockchain can be "stored" by storing the hashes of data, such that you can at least verify that thats the datum whose hash was stored if you have the datum to hash yourself and check against the one in the blockchain.A merkle tree is one way of doing this.So to construct a merkle tree you make a tree data structure with each of the leaf nodes containing the hash of a section of the data to be stored.From there you take the hash of the concatenation of the child nodes, and propagate the value up to the parent, continuing this process up the tree until a final hash is generated.

A blocks header is the top hash of applying the merkle procedure to a the data contained in the block.Thus even if a block has a large number of transactions all that is stored is the root hash of the merkle tree.Any changes to the source will be apparent if the same merkle procedure is applied to both files, small changes at the leaves propagate upwards and change the resultant hash.An interesting lemma is that as a "storage" mechanism, hashes are "lossy" such that starting with a 2000 character file, and eventually getting a 40 digit hex number; The original encoding of 2000 characters with 78 possible characters(making bounds on this approximation) has 9.582e+3772 possible files that could be represented, while the hashing function can only map that range to 1.106e+47 ouputs in the domain.buying bitcoin with moneypakThat's still a large domain, so hash collisions (when to inputs map to the same ouptut) would be extremely rare.bitcoin virus avast

Browse other questions tagged blockchain hash block-header hash-algorithm ethash or ask your own question._ Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top up vote down vote favorite 2 The block hash has to be below certain difficulty, right?In bitcoin this means, that there are many leading zeroes in hash value, eg.for bitcoin block #402329 hash is 000000000000000006efd706f4467e2d7ed6f0fed757ca7d59e2cc8c81a2d9e3.asic bitcoin mining gearBut for the ethereum blockchain the hash of block #1138224 is 0xa4f80a26aecb5fc975e12a9d3d0f6a7907c60b1d7e6b5205dfb4c984dad7f1ba.bitcoin naira calculatorWhy are there no leading zeroes?bitcoin domain parking

blocks hash block-header difficulty up vote 7 down vote In the Ethereum blockchain, the difficulty is used to calculate a target./block/1257006 : ℹ 35:02:42.89 ethminer Solution found; Submitting to http://192.168.4.120:8545 ... ℹ 35:02:42.89 ethminer Nonce: ff4136b6b6a244ec ℹ 35:02:42.89 ethminer Mixhash: 47da5e47804594550791c24331163c1f1fde5bc622170e83515843b2b13dbe14 ℹ 35:02:42.89 ethminer Header-hash: f5afa3074287b2b33e975468ae613e023e478112530bc19d4187693c13943445 ℹ 35:02:42.89 ethminer Seedhash: 1730dd810f27fdefcac730fcab75814b7286002ecf541af5cdf7875440203215 ℹ 35:02:42.89 ethminer Target: 00000000000baef6895d630131521d65d984555906990f43f352be4350291f92 ℹ 35:02:42.89 ethminer Ethash: 0000000000095d18875acd4a2c2a5ff476c9acf283b4975d7af8d6c33d119c74 ℹ 35:02:42.89 ethminer B-) Submitted and accepted.bitcoin difficulty riseHere is a snippet of Java to compute the difficulty from the target : import java.math.BigInteger; public class DifficultyDemo { public static void main(String[] args) { BigInteger numTwoPow256 = new BigInteger("2").pow(256); BigInteger target = new BigInteger("00000000000baef6895d630131521d65d984555906990f43f352be4350291f92", 16); BigInteger difficulty = numTwoPow256.divide(target); System.out.println(difficulty.toString()); } } And the difficulty is calculated as 24091770185844 which corresponds to the difficulty in the blockchain explorer screen.mine-litecoin server

We can use ethminer --check-pow to check the proof-of-work for validity as follows: beefee@Rasterbator:~$ ethminer --check-pow f5afa3074287b2b33e975468ae613e023e478112530bc19d4187693c13943445 1730dd810f27fdefcac730fcab75814b7286002ecf541af5cdf7875440203215 24091770185844 ff4136b6b6a244ec VALID :-) 0000000000095d18875acd4a2c2a5ff476c9acf283b4975d7af8d6c33d119c74 < 00000000000baef6895d630131521d65d984555906990f43f352be4350291f93 where 00000000000baef6895d630131521d65d984555906990f43f352be4350291f93 = 2^256 / 24091770185844 and 0000000000095d18875acd4a2c2a5ff476c9acf283b4975d7af8d6c33d119c74 = ethash(f5afa3074287b2b33e975468ae613e023e478112530bc19d4187693c13943445, ff4136b6b6a244ec) with seed as 1730dd810f27fdefcac730fcab75814b7286002ecf541af5cdf7875440203215 (mixHash = 47da5e47804594550791c24331163c1f1fde5bc622170e83515843b2b13dbe14) SHA3( light(seed) ) = 35ded12eecf2ce2e8da2e15c06d463aae9b84cb2530a00b932e4bbc484cde353 The miner's GPU would iterate through a range of random Nonces.java bitcoin blockchain

This Nonce, combined with the Seedhash and Header-hash using a hash function need to calculate a number below the Target.If this calculated number is below the target, the miner has successfully mined a block and the block details will be submitted to the Ethereum network nodes.In the example above, the calculated hash Ethash is larger than the Target and is therefore an incorrectly mined block (which is mentioned in the bug report).In Bitcoin, the target is the block hash.bitcoin input scriptAs difficulty rises, you will see the number of leading zeroes increase.Block 405390 (https://blockchain.info/block/00000000000000000320554ad0db0c0766bd3a83dc1ec1b1c1045274d73d5d37) has 17 leading zeroes.Block 40539 (https://blockchain.info/block/000000001ace7f4aa75ba7cd7a2fc3d2164638fabf8c617afd538b0369148cb6) has 8 leading zeroes (mined in 2010).The Ethereum Target is sort of equivalent to the Bitcoin block hash.up vote 4 down vote What you see in block explorers is the sha3 of the block header, not the ethash.