如何计算chain_id？

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1 个回答

Tom · Accepted Answer · 2019-02-27

chain_id是根据创世块哈希计算得出的,如下所示.

首先,使用伪代码:

 tezosB58CheckEncode('Net',
  firstFourBytes(
    blake2b(msg = tezosB58CheckDecode('B', genesisBlockHash),
            size = 32)))

详细信息:

进行创世块哈希.例如,在主网中,这是"BLockGenesisGenesisGenesisGenesisGenesisf79b5d1CoW2".
Base58Check-decode块哈希.您可以通过在tezos.git中执行git grep B\(来看到),块" B"的前缀字节为[1,52](十进制).这为我们提供了0x8fcf233671b6a04fcf679d2a381c2544ea6c1ea29ba6157776ed8424c7ccd00b.
计算块哈希字节的BLAKE2B哈希(大小32).我们得到0x7a06a7709ff405d1791d856c52a3c55246e03ec913599b813ec2977398afb3be.仅取前四个字节0x7a06a770.
Base58Check-encode这四个字节的前缀为" Net" [87,82,0](git grep Net\().我们得到"NetXdQprcVkpaWU".

对于协议更新测试链,我相信'genesis'块将是主链中派生测试链的块.

The chain_id is computed from the genesis block hash as follows.

First, in pseudocode:

tezosB58CheckEncode('Net',
  firstFourBytes(
    blake2b(msg = tezosB58CheckDecode('B', genesisBlockHash),
            size = 32)))

In detail:

Take the genesis block hash. For example, in mainnet, this is "BLockGenesisGenesisGenesisGenesisGenesisf79b5d1CoW2".
Base58Check-decode the block hash. The prefix bytes for blocks "B" are [1, 52] (in decimal), as you can see by doing git grep B\( in tezos.git. This gives us 0x8fcf233671b6a04fcf679d2a381c2544ea6c1ea29ba6157776ed8424c7ccd00b.
Compute the BLAKE2B hash (size 32) of the block hash bytes. We get 0x7a06a7709ff405d1791d856c52a3c55246e03ec913599b813ec2977398afb3be. Take only the first four bytes, 0x7a06a770.
Base58Check-encode these four bytes with the "Net" prefix [87, 82, 0] (git grep Net\(). We get "NetXdQprcVkpaWU".

For a protocol update test chain, I believe the 'genesis' block will be the block in the main chain from which the test chain was forked.

You can find this computation defined in lib_crypto/chain_id.ml and then used as Chain_id.of_block_hash in various places (e.g. lib_shell/state.ml, lib_shell/chain_validator.ml, lib_storage/context.ml).