Ca signature is an electronic signature, which is a manifestation of electronic signature. Image processing technology is used to transform the electronic signature operation into the same visual effect as the stamping operation of paper documents, and electronic signature technology is used to ensure the authenticity and integrity of electronic information and the non-repudiation of signers.

With the popularity of the Internet and the rapid development of various e-commerce activities and e-government activities, electronic signature has been widely used in various fields, mainly including: sending secure e-mail, visiting secure websites, online bidding, online signing, online ordering, secure online file transmission, online payment, online tax payment, online stock trading, online shopping and online customs declaration.

The practice in developed countries is mainly solved by electronic signature. In fact, the electronic signature itself is not a "signature", but an asymmetric public key security system, and its operation mode is essentially a mathematical operation. Here, encryption refers to a technical process of hiding the transmitted information content-that is, closely combining the mathematically existing relationship with a key (public key and private key).