以太坊区块hash的计算

作者: 古则 | 来源:发表于2017-12-09 17:36 被阅读89次

    在上一篇以太坊rlp编解码规则及实现中,我们看到了字符数组编解码的实现,下面在计算以太坊区块hash时,我们会看到rlp列表编码的使用

    以太坊区块头

    首先请看go-ethereum中以太坊区块头的定义

    type Header struct {
        ParentHash  common.Hash    `json:"parentHash"       gencodec:"required"`
        UncleHash   common.Hash    `json:"sha3Uncles"       gencodec:"required"`
        Coinbase    common.Address `json:"miner"            gencodec:"required"`
        Root        common.Hash    `json:"stateRoot"        gencodec:"required"`
        TxHash      common.Hash    `json:"transactionsRoot" gencodec:"required"`
        ReceiptHash common.Hash    `json:"receiptsRoot"     gencodec:"required"`
        Bloom       Bloom          `json:"logsBloom"        gencodec:"required"`
        Difficulty  *big.Int       `json:"difficulty"       gencodec:"required"`
        Number      *big.Int       `json:"number"           gencodec:"required"`
        GasLimit    *big.Int       `json:"gasLimit"         gencodec:"required"`
        GasUsed     *big.Int       `json:"gasUsed"          gencodec:"required"`
        Time        *big.Int       `json:"timestamp"        gencodec:"required"`
        Extra       []byte         `json:"extraData"        gencodec:"required"`
        MixDigest   common.Hash    `json:"mixHash"          gencodec:"required"`
        Nonce       BlockNonce     `json:"nonce"            gencodec:"required"`
    }
    

    存在两种区块hash值
    (1)header_hash_nononce,eth.getWork获取的第一个字段就是这个,这个hash是对header除 MixDigest,Nonce外进行rlp编码后进行hash得到的
    (2)header_hash, eth.getBlock得到的数据中的hash就是这个,这个hash是对整个header进行rlp编码后进行hash得到的

    注意:
    上面所说的rlp编码是指将header的各个字段看作一个列表进行编码
    上面所说的hash是指keccakf 256算法,keccakf是sha3所采用的hash算法,算法可参见ethash算法库

    区块头rlp编码及hash的计算

    int start_index = 0;
    int data_index = 1 + 8;
    char buf[4096] = {0};
    void *p = buf + data_index;
    size_t left = sizeof(buf) - data_index;
    rlp_pack_buf(&p, &left, parent_hash_bin, sdslen(parent_hash_bin));
    rlp_pack_buf(&p, &left, uncles_hash_bin, sdslen(uncles_hash_bin));
    rlp_pack_buf(&p, &left, miner_bin, sdslen(miner_bin));
    rlp_pack_buf(&p, &left, state_root_bin, sdslen(state_root_bin));
    rlp_pack_buf(&p, &left, tx_hash_bin, sdslen(tx_hash_bin));
    rlp_pack_buf(&p, &left, receipt_hash_bin, sdslen(receipt_hash_bin));
    rlp_pack_buf(&p, &left, bloom_bin, sdslen(bloom_bin));
    rlp_pack_buf(&p, &left, diff_bin, sdslen(diff_bin));
    rlp_pack_buf(&p, &left, number_bin, sdslen(number_bin));
    rlp_pack_buf(&p, &left, gas_limit_bin, sdslen(gas_limit_bin));
    rlp_pack_buf(&p, &left, gas_used_bin, sdslen(gas_used_bin));
    rlp_pack_buf(&p, &left, time_bin, sdslen(time_bin));
    rlp_pack_buf(&p, &left, extra_data_bin, sdslen(extra_data_bin));
     //不包含这两个就是header_hash_nononce
    rlp_pack_buf(&p, &left, mixdigest_bin, sdslen(mixdigest_bin));
    rlp_pack_buf(&p, &left, nonce_bin, sdslen(nonce_bin));
    
    //列表前缀的处理
    size_t alllen = sizeof(buf) - data_index - left;
     if (alllen <= 55) {
            start_index = data_index - 1; 
            buf[start_index] = 192 + alllen;
    } else {
            char len_buf[8] = {0};
            void *len_buf_p = len_buf;
            size_t len_buf_left = sizeof(len_buf);
            int space = rlp_pack_varint_be(&len_buf_p, &len_buf_left, alllen);
            start_index = data_index - 1 - space;
            buf[start_index] = 247 + space;
            memcpy(buf + start_index + 1, len_buf, space);
    }
    size_t buf_alllen = sizeof(buf) - left - start_index;
    sds hash = sdsnewlen(NULL, 32);
    sha3_256((uint8_t *)hash, 32, (uint8_t*)(buf + start_index), buf_alllen);
    return hash;
    

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