Page 251 - 《软件学报》2020年第12期

任艳丽 等:可修改的区块链方案 3917

签值,实现对有向无环图的恢复.每一轮空间竞争中,系统将充当验证者向矿工充当的证明者发起挑战,记为
C(c 1 ,c 2 ,…,c k ),也即顶点序号集合.证明者需返回 C 中各顶点对应的标签值.很显然,空间越大,存储的顶点越多,越
能尽快返回结果.存储顶点数少的证明者只能牺牲时间,计算未存储的顶点标签值再返回.因此空间越大,竞争
成功概率越高.以上便是基于空间竞争的挖矿过程,具体细节详见文献[10].本实验模拟多次竞争过程,记录不同
挑战下各矿工的证明时间,部分结果如表 2 所示.

Fig.9 Directed graph of system
图 9 系统有向图
Table 1 Store information of the miner vertex in directed graph
表 1 矿工有向图顶点存储信息
矿工 存储有向图顶点号
1 18,4,3,12,11,9,17,14
2 18,4,3,12,11,9,17,14,19,2,1,5
3 18,4,3,12,11,9,17,14,19,2,1,5,6,7
4 18,4,3,12,11,9,17,14,19,2,1,5,6,7,0,13
5 18,4,3,12,11,9,17,14,19,2,1,5,6,7,0,13,15,16,8,10
6 18,4,3,12,11,9,17,14,19,2
7 18,4,3,12,11,9,17,14,19,2,1,5,6,7,0,13,15,16
8 18,4,3,12,11,9,17,14,19,2,1,5,6,7,0,13,15,16,8,10,25,21
9 18,4,3,12,11,9,17,14,19,2,1,5,6,7,0,13,15,16,8,10,25,21,20
10 18,4,3,12,11,9,17,14,19,2,1,5,6,7,0,13,15,16,8,10,25,21,20,22,23
Table 2 Space proof time comparison of multiple miners
表 2 多名矿工空间证明时间比较
C={19,15,22, C={1,6,13,10,4, C={18,4,3,2,1,5,13,0, C={18,4,3,12,11,9,17,14,19,
C={20,7,21,
24,7,8,23, 0,25,12,11,22, 7,6,16,8,15,10,25, 2,1,5,13,0,7,6,16,8,15,10,
10,22}
0,20,5} 2,7,24,8,23} 21,24,20,22,23} 25,21, 24, 20, 22, 23}
1 2.521s 2.990s 3.131s 3.246s 3.377s
6 2.103s 2.417s 2.610s 2.747s 2.800s
2 1.157s 1.471s 1.607s 1.793s 1.803s
3 0.843s 1.124s 1.320s 1.504s 1.633s
4 0.510s 0.913s 1.007s 1.154s 1.243s
7 0.421s 0.680s 0.804s 1.000s 1.077s
5 0.253s 0.531s 0.660s 0.750s 0.857s
8 0.163s 0.430s 0.470s 0.720s 0.807s
9 0.127s 0.367s 0.390s 0.567s 0.687s
10 0.110s 0.307s 0.350s 0.443s 0.590s
由表 2 可以看出:本地空间越大、存储顶点数越多的证明者即矿工 10,返回证明结果的时间越短,成功挖矿
概率越大.这符合 Pospace 共识机制下,区块记账权竞争的基本过程.