iOS8指紋識別TouchID

標籤：ios8   指紋識別   touchid   objective-c   解鎖   

      蘋果在2014年6月3日的WWDC2014開幕式上推出了新版iOS8系統，介面上iOS8與iOS7相比變化不大，不過在功能方面進行了完善。iOS8通知中樞更加強大，支援訊息直接回複操作，並支援QuickType和第三方IME。簡訊功能改進明顯，支援群聊，發送語音、視頻，分享地理位置等。從終端使用者的角度看，iOS8的許多新功能早已出現在其他平台中。iOS8會向第三方軟體開放TouchID訪問，這意味著可以使用該感應器登陸銀行應用等。

      第三方應用可以使用TouchID介面，意味著未來的很多應用都可以用指紋識別功能了。你可以選擇Touch ID登陸第三方應用程式，不需要輸入密碼，你的指紋資料是被保護的，在沒有被允許的情況下別的程式是訪問不到它的。

                                

      根據蘋果的解釋，一個單一的註冊指紋與別人指紋出現隨機匹配的機率為五萬分之一。

      蘋果聲稱“Secure Enclave”模組系統能夠安全地管理並識別使用者的指紋，並將使用者的指紋資訊獨立地儲存在別的系統中，同時通過加密記憶體和一個硬體隨機數字密碼發生器進行管理。

      每個“Secure Enclave”是單獨設定的，不能訪問系統其他部分的，擁有自己的獨立的UID（唯一的ID），連蘋果也不知道這些UID。當裝置啟動時，Touch ID會臨時建立一個秘鑰，與“Secure Enclave”的UID配合，對裝置的記憶體空間進行加密。

      而在蘋果發布的檔案中，蘋果對A7處理器進行指紋識別授權的描述是：A7和Touch ID之間通過一個串列外設介面匯流排進行通訊。A7處理器將資料發到“Secure Enclave”，但並不對資料內容進行讀取。加密和身分識別驗證都是使用Touch ID和“Secure Enclave”之間的共用密鑰。通訊金鑰交換使用雙方提供的一個隨機AES密鑰，並隨機建立工作階段金鑰和使用AES-CCM傳輸加密。

      據瞭解：iPhone 5s中的指紋感應器檢測到的表皮上突起的紋線。它檢測到的不是使用者手指外部的死皮指紋，這種指紋很容易被複製。iPhone 5s的指紋感應器利用射頻訊號，檢測使用者手指表面下方那一層皮膚的“活”指紋。如果手指與人的身體分離，那麼感應器是無法檢測到這種指紋的。所以使用者不用擔心自己的指紋被複製或盜竊之後，被用於解鎖裝置，因為感應器是無法識別這種“死”指紋的。

      最近研究了下iOS8的文檔，對指紋識別瞭解了下，並下載了一個官方提供的Demo。但是

      NS_CLASS_AVAILABLE(10_10, 8_0)

      從這句中可以看出，要想使用TouchID的介面，電腦的mac系統必須是10.10的，手機iOS系統必須是8.0，所以為了這個Demo我也沒有升級電腦系統(畢竟還不穩定)。但根據Demo中的代碼和文檔可以看出，TouchID的基本用法。

1.首先要使用TouchID，要先匯入依賴包：LocalAuthentication.framework。

2.檢查裝置是否能用TouchID，返回檢查結果BOOL類型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.如果裝置能使用TouchID，代碼塊中返回識別結果BOOL類型的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.對於檢查和識別的兩個方法在 LocalAuthentication.framework/Headers/LAContext.h 中定義的：

/// 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;

歡迎小夥伴們對測試結果檢驗一下啊！

（轉載請註明出處，謝謝！http://blog.csdn.net/yujianxiang666/article/details/35280025）