TXIDs and intermediate hashes are always in internal byte order when they're concatenated, and the resulting merkle root is also in internal byte order when it's placed in the block header. Once a row is obtained with only two hashes, those hashes are concatenated and hashed to produce the merkle root. If there are more than two hashes in the second row, the process is repeated to create a third row (and, if necessary, repeated further to create additional rows). If there are an odd (non-even) number of TXIDs, the last TXID is concatenated with a copy of itself and hashed. Each pair is concatenated together as 64 raw bytes and SHA256(SHA256()) hashed to form a second row of hashes. The TXIDs are placed in order and paired, starting with the coinbase transaction's TXID. If a block has three or more transactions, intermediate merkle tree rows are formed. If a block only has a coinbase transaction and one other transaction, the TXIDs of those two transactions are placed in order, concatenated as 64 raw bytes, and then SHA256(SHA256()) hashed together to form the merkle root. If a block only has a coinbase transaction, the coinbase TXID is used as the merkle root hash. This ensures that any program parsing block chain transactions linearly will encounter each output before it is used as an input. However, the TXID corresponding to the output must be placed at some point before the TXID corresponding to the input. The coinbase transaction's TXID is always placed first.Īny input within this block can spend an output which also appears in this block (assuming the spend is otherwise valid). The merkle root is constructed using all the TXIDs of transactions in this block, but first the TXIDs are placed in order as required by the consensus rules: Draft BIP9 describes the version bits design as of this writing, although it is still being actively edited and may substantially change while in the draft state.
Bip65 reference miner full#
See BIP34 for a full description of this method.Īs of this writing, a newer method called version bits is being designed to manage future soft forking changes, although it's not known whether version 4 will be the last soft fork to use the IsSuperMajority() function. The mechanism used for the version 2, 3, and 4 upgrades is commonly called IsSuperMajority() after the function added to Dash Core to manage those soft forking changes. These blocks now support the new OP_CHECKLOCKTIMEVERIFY opcode described in that BIP. Version 4 blocks specified in BIP65 and introduced in Bitcoin Core 0.11.2 (November 2015) as a soft fork became active in December 2015. Transactions that do not use strict DER encoding had previously been non-standard since Dash Core 0.8.0. When the fork reached full enforcement, it required strict DER encoding of all ECDSA signatures in new blocks as described in BIP66. Soft fork (Block 244,834 was the first version 3 block). Version 3 blocks were introduced in Dash Core 0.11.2 (March 2015) as a
As described in BIP34, valid version 2 blocks require a block height parameter in the coinbase. Version 2 was introduced with the first block following the genesis block (January 2014). Version 1 was used by Dash for the genesis block only. Hash of previous block's headerħ0dda20810decd12bc9b048aaab31471. The hashes are in internal byte order the other values are all in little-endian order.Īn example header in hex: 02000000. If all 32-bit values are tested, the time can be updated or the coinbase transaction can be changed and the merkle root updated. See the nBits format described below.Īn arbitrary number miners change to modify the header hash in order to produce a hash less than or equal to the target threshold. Full nodes will not accept blocks with headers more than two hours in the future according to their clock.Īn encoded version of the target threshold this block's header hash must be less than or equal to. Must be strictly greater than the median time of the previous 11 blocks. The block time is a Unix epoch time when the miner started hashing the header (according to the miner).
The merkle root is derived from the hashes of all transactions included in this block, ensuring that none of those transactions can be modified without modifying the header. This ensures no previous block can be changed without also changing this block's header.Ī SHA256(SHA256()) hash in internal byte order. See the list of block versions below.Īn X11() hash in internal byte order of the previous block's header. The block version number indicates which set of block validation rules to follow.
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