iOS提供一種安全的存儲數據的方式，就是鑰匙串，想要在app中使用鑰匙串，首先要開啟鑰匙串訪問的功能，即在app server中勾選Data Protection功能，就像要通知一樣，需要開啟改功能。如下圖：

屏幕快照.png

同時使用精準app ID如下圖：

屏幕快照.png

打開電腦鑰匙串，察看存儲在鑰匙串數據，如圖，ios和mac是相似的。

CAA368D2-5497-492F-BF6A-37A414C5D9D6.png

對應的屬性
kSecClass-- 上圖中的種類
kSecAttrService--上圖中的位置
kSecAttrAccount--上圖中的賬戶
kSecValueData--上圖中的密碼

添加數據：SecItemAdd

 NSString *key = @"pwd";
    NSString *value = @"password";
    NSData *valueData = [value dataUsingEncoding:NSUTF8StringEncoding];
    NSString *service = [[NSBundle mainBundle] bundleIdentifier];
    NSDictionary *dict = @{
                           (__bridge id)kSecClass:(__bridge id)kSecClassGenericPassword,
                           (__bridge id)kSecAttrService:service,
                           (__bridge id)kSecAttrAccount:key,
                           (__bridge id)kSecValueData:valueData
                           };
    CFTypeRef typeResult = NULL;
    OSStatus state =  SecItemAdd((__bridge CFDictionaryRef)dict, &typeResult);
    if (state == errSecSuccess) {
        NSLog(@"store secceed");
    }

查詢屬性：SecItemCopyMatching

//查找
-(void)findAttr
{
    NSString *key = @"pwd";
    NSString *service = [[NSBundle mainBundle] bundleIdentifier];
    NSDictionary *dict = @{
                           (__bridge id)kSecClass:(__bridge id)kSecClassGenericPassword,
                           (__bridge id)kSecAttrService:service,
                           (__bridge id)kSecAttrAccount:key,
                           (__bridge id)kSecReturnAttributes:(__bridge id)kCFBooleanTrue
                           };
    CFDictionaryRef resultDict = NULL;
    OSStatus state = SecItemCopyMatching((__bridge CFDictionaryRef)dict, (CFTypeRef*)&resultDict);
    NSDictionary *result = (__bridge_transfer NSDictionary*)resultDict;
    if (state == errSecSuccess)
    {
        NSLog(@"server:%@",result[(__bridge id)kSecAttrService]);
        NSLog(@"account:%@",result[(__bridge id)kSecAttrAccount]);
        NSLog(@"assessGroup:%@",result[(__bridge id)kSecAttrAccessGroup]);
        NSLog(@"createDate:%@",result[(__bridge id)kSecAttrCreationDate]);
        NSLog(@"modifyDate:%@",result[(__bridge id)kSecAttrModificationDate]);
    }
}

當在字典中添加kSecReturnAttributes并設置為yes時，表示查詢鑰匙串數據的屬性，SecItemCopyMatching的第二個參數為字典。
查詢數據：SecItemCopyMatching

//查找數據
-(void)findData
{
    NSString *key = @"pwd";
    NSString *server = [[NSBundle mainBundle] bundleIdentifier];
    NSDictionary *queueDict = @{
                                (__bridge id)kSecClass:(__bridge id)kSecClassGenericPassword,
                                (__bridge id)kSecAttrService:server,
                                (__bridge id)kSecAttrAccount:key,
                                (__bridge id)kSecReturnData:(__bridge id)kCFBooleanTrue
                                /*(__bridge id)kSecMatchLimit : (__bridge id)kSecMatchLimitAll
                                 當為kSecMatchLimit時，SecItemCopyMatching第二個參數為CFArrayRef，元素為CFDataRef*/
                                };
    CFDataRef dataRef = NULL;
    OSStatus state = SecItemCopyMatching((__bridge CFDictionaryRef)queueDict, (CFTypeRef*)&dataRef);
    if (state == errSecSuccess) {
        NSString *value = [[NSString alloc] initWithData:(__bridge_transfer NSData*)dataRef encoding:NSUTF8StringEncoding];
        NSLog(@"value:%@",value);
    }
}

當在字典中添加kSecReturnData并設置為yes時，表示查詢鑰匙串數據的數據，SecItemCopyMatching的第二個參數為CFDataRef。當在字典中添加了kSecMatchLimit 時并設置為kSecMatchLimitAll會返回所有的，SecItemCopyMatching第二個參數為CFArrayRef，元素為CFDataRef。

更新數據：SecItemUpdate

-(void)updateData
{
    NSString *key = @"pwd";
    NSString *server = [[NSBundle mainBundle] bundleIdentifier];
    NSDictionary *queue = @{
                            (__bridge id)kSecClass:(__bridge id)kSecClassGenericPassword,
                            (__bridge id)kSecAttrService:server,
                            (__bridge id)kSecAttrAccount:key
                            };
    OSStatus state = SecItemCopyMatching((__bridge CFDictionaryRef)queue, NULL);
    //存在修改
    if (state == errSecSuccess) {
        NSString *newValue = @"new Value";
        NSData *newData = [newValue dataUsingEncoding:NSUTF8StringEncoding];
        NSDictionary *paramDict = @{
                                    (__bridge id)kSecValueData:newData
                                    };
        OSStatus updateState = SecItemUpdate((__bridge CFDictionaryRef)queue, (__bridge CFDictionaryRef)paramDict);
        if (updateState == errSecSuccess) {
            NSLog(@"更新成功");
        }
    }
}

刪除鑰匙串：SecItemDelete

-(void)deleteData
{
    NSString *key = @"pwd";
    NSString *server = [[NSBundle mainBundle] bundleIdentifier];
    NSDictionary *queue = @{
                            (__bridge id)kSecClass:(__bridge id)kSecClassGenericPassword,
                            (__bridge id)kSecAttrService:server,
                            (__bridge id)kSecAttrAccount:key
                            };
    OSStatus state = SecItemCopyMatching((__bridge CFDictionaryRef)queue, NULL);
    //存在
    if (state == errSecSuccess) {
        OSStatus deleteState = SecItemDelete((__bridge CFDictionaryRef)queue);
        if (deleteState == errSecSuccess) {
            NSLog(@"刪除成功!!!");
        }
    }
}

總結：鑰匙串使用感覺還是挺有用的，今天特意研究了一下，還有兩個同一個開發者發布的app之間可以共享鑰匙串數據，Sharing Keychain Data Between Multiple Apps，下次有時間研究一下，下次再更新。
簡單demo：https://github.com/jiangtaidi/KeyChainPro.git