4. The method according to claim 1 , wherein a single character is associated with at least two keys on the keyboard.
1. A password authentication method, comprising: generating a first virtual keyboard as a keyboard; generating a group of sequential candidate characters according to a user's operations to the keyboard, at least one key on the keyboard being associated with at least two characters, wherein the user's single operation of any one key results in characters associated with that key being selected as candidate characters with the same ranking; authenticating whether a character string formed by the sequential candidate characters matches a password of the user; generating a different second virtual keyboard in response to a character string formed by the sequential candidate characters matching the password of the user, at least one key on the second virtual keyboard being associated with at least two characters, the second virtual keyboard having a different character layout than the first virtual keyboard such that character combinations on keys of the second virtual keyboard are different from character combinations on keys of the first virtual keyboard, wherein each key on the second virtual keyboard is associated with a different number of characters; generating a second group of sequential candidate characters according to the user's operations to the second virtual keyboard, wherein the user's single operation of any one key on the second virtual keyboard results in characters associated with that key are selected as candidate characters having same ranking; and authenticating whether one of character strings formed by the second group of sequential candidate characters matches the password of the user.