Compare audio files for Voice Authentication

I am developing an Iphone application. This application is used to store user personal data. To ensure security, we strive to provide a new feature in our application, the user can access the data after entering the application. The problem is that we need to provide Voice Authentication . This means that the user can save the word "hello" as a password by writing it down. If he needs to enter our application, he must say the word "hello." And these two sounds are compared, and if they match, the user will be authenticated and login will be allowed. Is such an application possible? Can I compare voices in Iphone?

I researched these links, but did not get Ideas. Please help me. http://developer.apple.com/library/mac/#documentation/AVFoundation/Reference/AVAudioPlayerClassReference/Reference/Reference.html

https://developer.apple.com/library/mac/#documentation/AVFoundation/Reference/AVAudioRecorder_ClassReference/Reference/Reference.html

https://developer.apple.com/library/mac/#documentation/musicaudio/reference/CoreAudioDataTypesRef/Reference/reference.html