The function and principle of verification Code _ network

The word captcha was first introduced in 2002 by Luis von Ahn of Mellon University, Manuel Blum, Nicholas J.hopper, and John Langford of IBM. The authentication code is the abbreviation for completely automated public Turing test to tell Computers and humans apart, in Chinese meaning "fully automatic distinguishing between computer and human Turing tests". In fact, the verification code is a series of randomly generated numbers or symbols, to generate a picture, the picture with some interference elements, the user to identify the human eye The authentication code information, and then enter the form to submit the site verification, verify the success of the use of a feature.

The verification code is usually used in the Web interface of user login or message, when the user enters the authentication code in the browser, the user name, password and authentication code are submitted to the server, the server-side gets the user's submission, and determines whether the user-submitted authentication code characters are the same as those stored on the server side. If the same is true, the user submits the information by validating the message, otherwise the prompt for validation is not prompted.

Verification Code verification principles and procedures as shown in Figure 4.1. Fig. 4.1 Principle and process of verification code verification