The paper analyzes the one - way hash function ( sha - 1 ) and study the process of gaining keks from ak using sha - 1 . this paper discusses the state models of key management protocol in bpi + system and key usage 分析討論了單向散列函數(shù)的安全散列算法( sha - 1 ) ,研究了ak進(jìn)行必要的填充后使用sha - 1得到密鑰加密密鑰( kek )的過程。