How ever, we will show that their modification scheme is also insecure.Any original signer or proxy signer can forge a valid proxy signature, and the delegation time can he revised.

• 本文指出，周红生等的方案也是不安全的，任一原始签名人或任一代理人都能生成有效的代理多重签名，而且可以任意修改代理签名的期限。