iOS8新增了LocalAuthentication框架，用于TouchID的授权使用。亲測，眼下须要用户的设备支持指纹识别并已设置锁屏，并且实际測试过程中反馈比較慢。不能直接跟第三方账号password绑定，假设须要实现第三方应用直接指纹识别登录，须要在本地存储账号信息，指纹识别通过之后再从本地读取账号信息登录。总之。眼下的指纹识别是跟设备、设备锁屏password绑定的。

測试代码：

///使用TouchID
-(void)usingTouchID
{
    LAContext *myContext = [[[LAContext alloc] init] autorelease];
    NSError *authError = nil;
    NSString *myLocalizedReasonString = @"用于指纹登录";
    if ([myContext canEvaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics error:&authError]) {
        [myContext evaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics
                  localizedReason:myLocalizedReasonString
                            reply:^(BOOL success, NSError *error) {
                                if (success) {
                                    // User authenticated successfully, take appropriate action
                                    NSLog(@"成功");
                                    UIAlertView *alertView = [[[UIAlertView alloc] initWithTitle:@"Suceess" message:@"已通过指纹识别。" delegate:self cancelButtonTitle:nil otherButtonTitles:@"OK", nil] autorelease];
                                    [alertView show];
                                } else {
                                    // User did not authenticate successfully, look at error and take appropriate action
                                    NSLog(@"fail with error:%@",error);
                                    UIAlertView *alertView = [[[UIAlertView alloc] initWithTitle:@"Failed" message:[error localizedDescription] delegate:self cancelButtonTitle:nil otherButtonTitles:@"OK", nil] autorelease];
                                    [alertView show];
                                }
                            }];
    } else {
        // Could not evaluate policy; look at authError and present an appropriate message to user
        NSLog(@"auth with error:%@",authError);
        UIAlertView *alertView = [[[UIAlertView alloc] initWithTitle:@"Failed" message:[authError localizedDescription] delegate:self cancelButtonTitle:nil otherButtonTitles:@"OK", nil] autorelease];
        [alertView show];
    }
}