苹果在2014年6月3日的WWDC2014开幕式上推出了新版iOS8系统，界面上iOS8与iOS7相比变化不大，不过在功能方面进行了完善。iOS8通知中心更加强大，支持消息直接回复操作，并支持QuickType和第三方输入法。短信功能改进明显，支持群聊，发送语音、视频，分享地理位置等。从终端用户的角度看，iOS8的许多新功能早已出现在其他平台中。iOS8会向第三方软件开放TouchID访问，这意味着可以使用该感应器登陆银行应用等。
第三方应用可以使用TouchID接口，意味着未来的很多应用都可以用指纹识别功能了。你可以选择Touch ID登陆第三方应用程序，不需要输入密码，你的指纹数据是被保护的，在没有被允许的情况下别的程序是访问不到它的。
根据苹果的解释，一个单一的注册指纹与别人指纹出现随机匹配的概率为五万分之一。
苹果声称“Secure Enclave”模块系统能够安全地管理并识别用户的指纹，并将用户的指纹信息独立地保存在别的系统中，同时通过加密内存和一个硬件随机数字密码发生器进行管理。
每个“Secure Enclave”是单独设置的，不能访问系统其他部分的，拥有自己的独立的UID（唯一的ID），连苹果也不知道这些UID。当设备启动时，Touch ID会临时创建一个秘钥，与“Secure Enclave”的UID配合，对设备的内存空间进行加密。
而在苹果发布的文件中，苹果对A7处理器进行指纹识别授权的描述是：A7和Touch ID之间通过一个串行外设接口总线进行通信。A7处理器将数据发到“Secure Enclave”，但并不对数据内容进行读取。加密和身份验证都是使用Touch ID和“Secure Enclave”之间的共享密钥。通信密钥交换使用双方提供的一个随机AES密钥，并随机建立会话密钥和使用AES-CCM传输加密。
据了解：iPhone 5s中的指纹传感器检测到的表皮上突起的纹线。它检测到的不是用户手指外部的死皮指纹，这种指纹很容易被复制。iPhone 5s的指纹传感器利用射频信号，检测用户手指表面下方那一层皮肤的“活”指纹。如果手指与人的身体分离，那么传感器是无法检测到这种指纹的。所以用户不用担心自己的指纹被复制或盗窃之后，被用于解锁设备，因为传感器是无法识别这种“死”指纹的。
最近研究了下iOS8的文档，对指纹识别了解了下，并下载了一个官方提供的Demo。但是
NS_CLASS_AVAILABLE(10_10, 8_0)
从这句中可以看出，要想使用TouchID的接口，电脑的mac系统必须是10.10的，手机iOS系统必须是8.0，所以为了这个Demo我也没有升级电脑系统(毕竟还不稳定)。但根据Demo中的代码和文档可以看出，TouchID的基本用法。
1.首先要使用TouchID，要先导入依赖包：LocalAuthentication.framework。
2.检查设备是否能用TouchID，返回检查结果BOOL类型success：
LAContext *context = [[LAContext alloc] init];
__block NSString *msg;
NSError *error;
BOOL success;
// test if we can evaluate the policy, this test will tell us if Touch ID is available and enrolled
success = [context canEvaluatePolicy: LAPolicyDeviceOwnerAuthenticationWithBiometrics error:&error];
if (success) {
msg =[NSString stringWithFormat:NSLocalizedString(@"TOUCH_ID_IS_AVAILABLE", nil)];
} else {
msg =[NSString stringWithFormat:NSLocalizedString(@"TOUCH_ID_IS_NOT_AVAILABLE", nil)];
}
3.如果设备能使用TouchID，代码块中返回识别结果BOOL类型的success：
LAContext *context = [[LAContext alloc] init];
__block NSString *msg;
// show the authentication UI with our reason string
[context evaluatePolicy:LAPolicyDeviceOwnerAuthenticationWithBiometrics localizedReason:NSLocalizedString(@"UNLOCK_ACCESS_TO_LOCKED_FATURE", nil) reply:
^(BOOL success, NSError *authenticationError) {
if (success) {
msg =[NSString stringWithFormat:NSLocalizedString(@"EVALUATE_POLICY_SUCCESS", nil)];
} else {
msg = [NSString stringWithFormat:NSLocalizedString(@"EVALUATE_POLICY_WITH_ERROR", nil), authenticationError.localizedDescription];
}
}];
4.对于检查和识别的两个方法在 LocalAuthentication.framework/Headers/LAContext.h 中定义的：
/// Determines if a particular policy can be evaluated. /// /// @discussion Policies can have certain requirements which, when not satisfied, would always cause /// the policy evaluation to fail. Examples can be a passcode set or a fingerprint /// enrolled with Touch ID. This method allows easy checking for such conditions. /// /// Applications should consume the returned value immediately and avoid relying on it /// for an extensive period of time. At least, it is guaranteed to stay valid until the /// application enters background. /// /// @warning Do not call this method in the reply block of evaluatePolicy:reply: because it could /// lead to a deadlock. /// /// @param policy Policy for which the preflight check should be run. /// /// @param error Optional output parameter which is set to nil if the policy can be evaluated, or it /// contains error information if policy evaluation is not possible. /// /// @return YES if the policy can be evaluated, NO otherwise. - (BOOL)canEvaluatePolicy:(LAPolicy)policy error:(NSError * __autoreleasing *)error; /// Evaluates the specified policy. /// /// @discussion Policy evaluation may involve prompting user for various kinds of interaction /// or authentication. Actual behavior is dependent on evaluated policy, device type, /// and can be affected by installed configuration profiles. /// /// Be sure to keep a strong reference to the context while the evaluation is in progress. /// Otherwise, an evaluation would be canceled when the context is being deallocated. /// /// The method does not block. Instead, the caller must provide a reply block to be /// called asynchronously when evaluation finishes. The block is executed on a private /// queue internal to the framework in an unspecified threading context. Other than that, /// no guarantee is made about which queue, thread, or run-loop the block is executed on. /// /// Implications of successful policy evaluation are policy specific. In general, this /// operation is not idempotent. Policy evaluation may fail for various reasons, including /// user cancel, system cancel and others, see LAError codes. /// /// @param policy Policy to be evaluated. /// /// @param reply Reply block that is executed when policy evaluation finishes. /// /// @param localizedReason Application reason for authentication. This string must be provided in correct /// localization and should be short and clear. It will be eventually displayed in /// the authentication dialog subtitle. A name of the calling application will be /// already displayed in title, so it should not be duplicated here. /// /// @param success Reply parameter that is YES if the policy has been evaluated successfully or NO if /// the evaluation failed. /// /// @param error Reply parameter that is nil if the policy has been evaluated successfully, or it contains /// error information about the evaluation failure. /// /// @warning localizedReason parameter is mandatory and the call will throw NSInvalidArgumentException if /// nil or empty string is specified. /// /// @see LAError /// /// Typical error codes returned by this call are: /// @li LAErrorUserFallback if user tapped the fallback button /// @li LAErrorUserCancel if user has tapped the Cancel button /// @li LAErrorSystemCancel if some system event interrupted the evaluation (e.g. Home button pressed). - (void)evaluatePolicy:(LAPolicy)policy localizedReason:(NSString *)localizedReason reply:(void(^)(BOOL success, NSError *error))reply;
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（转载请注明出处，谢谢！http://blog.csdn.net/yujianxiang666/article/details/35280025）