Identity authentication method and system and password protection device

The invention provides an identity authentication method and system and a password protection device. The identity authentication method includes the steps that the password protection device and a server synchronously update dynamic sequence functions; the password protection device receives a user password inputted by a user; the password protection device utilizes the dynamic sequence function to carry out conversion on the user password so as to generate a first dynamic password, and then outputs the first dynamic password; the server utilizes the dynamic sequence function to carry out conversion on the user password, stored in the server, of the user so as to generate a second dynamic password; the server receives the first dynamic password, compares the first dynamic password with the second dynamic password and then confirms that the user is authenticated when the first dynamic password accords with the second dynamic password. Through the identity authentication method, the burden of the user for remembering the password is effectively relieved, and the identity authentication efficiency and security of identity information of the user are improved.