研究ras-256hash函数的结构安全性，给出三个sha-256变种函数，分别分析他们抵抗chabaud-joux攻击的能力与sha-256结构果比较，版权归作者所有，仅供研究。-Structural safety research the ras-256hash function, given three sha-256 variant function analysis their attacks against chabaud-joux ability sha-256 structure