普通的多级代理签名体制存在着诸多缺陷，如：原始签名人与各级代理签名人之间的抵赖问题，多级代理签名过长，签名验证计算量过大等等。作者就此诸多问题，基于离散对数这一数学难题，提出了一种安全的多级代理签名方案。该方案把各级代理签名人的秘密密钥嵌入最终的代理签名密钥中，解决了原始签名人与各级代理签名人之间互相抵赖的问题；把验证过程中的部分计算量移植到密钥生成过程中，从而降低了中间级验证和最终签名验证过程中的计算量，同时也缩短了多级代理签名的长度，实现了一种安全、高效的多级代理签名方案。

There are many problems in the multiple grade proxy signature schemes that are used nowadays. For example, the original signer and the proxy signers sometimes deny the truth of their signatures; the multiple grade proxy signatures usually have to be very long and the validating process of them are too complicated. To solve all these problems, a more secure multiple grade proxy signature scheme is proposed in this paper based on the study of a difficult mathematical concept, the discrete logarithm. Firstly, to ensure that none of the signers of all grades can deny their signatures, the private keys of all the proxy signers are put into the final proxy-signing key. Another feature of this scheme is that some calculation in the validating process is somehow transferred into the process of producing proxy-signing key. In this way, not only the validating of the signature is simplified, but also the multiple grade proxy signature can be effectively shortened. As a result, this paper achieve an efficient, secure multiple grade proxy signature scheme.