Abstract: By making the cryptanalysis to the blind proxy multi-signature schemes based on Nyberg-Rueppel signature scheme，it shows that suspending-factors are included in the scheme and in process of proxy key generation no private information of proxy signer is used.The attacking and forging are because of the existence of suspending-factors.A dishonest original signer can forge the proxy key and generate valid blind proxy signatures if in process of proxy key generation no private information of proxy signer is used.Against the security drawbacks，two improved schemes are proposed.In improved schemes，suspending-factors are avoided，private information of proxy signer is used in process of proxy key and analysis of security is given.

Key words: blind proxy signature, blind proxy multi-signature, suspending-factor, digital signature

摘要： 对基于Nyberg-Rueppel签名体制的盲代理多重签名方案进行密码分析，发现此方案中多处存在孤悬因子，且代理签名密钥不包含代理签名人的秘密密钥。对此方案的伪造攻击正是因为孤悬因子的存在，代理签名密钥不包含代理签名人的秘密密钥，则原始签名人可以伪造代理签名密钥并产生有效的盲代理签名。提出了两个对基于Nyberg-Rueppel签名体制的盲代理多重签明方案的改进方案，消除了孤悬因子，使代理签名密钥包含了代理签名人的秘密密钥;对改进后的方案进行了安全性分析。

关键词: 盲代理签名, 盲代理多重签名, 孤悬因子, 离散对数