The certificateless signature scheme can suffer from public key replacement attack so that any one can forge a valid signature on any message.

该方案能受到替换公钥攻击，以至于任何人都能对任何消息成功伪造签名。

youdao

Wrapping attacks aim at injecting a faked element into the message structure so that a valid signature covers the unmodified element while the faked one is processed by the application logic.

波鸿鲁尔大学专家在2009年发表的研究论文中阐述道：“包装攻击旨在向信息结构中注入一个伪造的元素，在应用逻辑处理伪造元素的同时，有效签名可以覆盖未改过的元素。

youdao

It USES a default signature algorithm, SHA1 with DSA, to create a self-signed certificate valid for 180 days.

它使用默认的签名算法(SHA1和DSA)创建一个带有自我签名的证书，有效期为180天。

youdao

An X mark is legal in most states as a valid signature.

FORBES: Taxes from A to Z: X Is For X-Mark (Signature)

Nobody knows for certain what constitutes a valid signature, nor whether a fresh petition can be presented if the first one is ruled invalid, nor even whether the president could stand again if voted out.

ECONOMIST: California comes to Caracas