Abstract: tA basic principle of modern cryptography is that “all secrets are in the secret key”. The cryptographic algorithm is publicly available, but the key must be kept confidential absolutely, to ensure the security of the cryptography and the information system. In this paper, through a review of the history about the digital signature key protection mechanism, we analyze the security features of these mechanisms, introduce the cloud collaborative key protection mechanism which emerge in recent years, and the research progress and the industrial practices about this mechanism, and also analyze the technical features, security, use scenarios and future trends of it，analyze the value of the cloud collaborative key protection mechanism and the influence to cryptographyic industry.

Key words: PKI, key protection, digital signature, multiparty calculation, threshold cryptography

摘要： 现代密码学的一个基本原则是：一切秘密寓于密钥之中.密码算法是可以公开的，密钥则必须绝对保密，这样才能确保密码和其保护信息的安全.通过对数字签名密钥保护机制的演变历史的回顾，分析了这些密钥保护机制的安全性特点，重点介绍了近年来出现的云端协同密钥保护机制，介绍了云端协同密钥保护相关的研究进展、产业实践，并分析了云端协同密钥保护机制的技术特点、安全性、适用场景以及将来的发展趋势，分析了云端协同密钥保护机制的应用价值和对密码行业发展的影响.

关键词: PKI, 密钥保护, 数字签名, 多方计算, 门限密码