iOS提供一种安全的存储数据的方式，就是钥匙串，想要在app中使用钥匙串，首先要开启钥匙串访问的功能，即在app server中勾选Data Protection功能，就像要通知一样，需要开启改功能。如下图：

屏幕快照.png

同时使用精准app ID如下图：

屏幕快照.png

打开电脑钥匙串，察看存储在钥匙串数据，如图，ios和mac是相似的。

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

对应的属性
kSecClass-- 上图中的种类
kSecAttrService--上图中的位置
kSecAttrAccount--上图中的账户
kSecValueData--上图中的密码

添加数据：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");
    }

查询属性：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]);
    }
}

当在字典中添加kSecReturnAttributes并设置为yes时，表示查询钥匙串数据的属性，SecItemCopyMatching的第二个参数为字典。
查询数据：SecItemCopyMatching

//查找数据
-(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
                                 当为kSecMatchLimit时，SecItemCopyMatching第二个参数为CFArrayRef，元素为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);
    }
}

当在字典中添加kSecReturnData并设置为yes时，表示查询钥匙串数据的数据，SecItemCopyMatching的第二个参数为CFDataRef。当在字典中添加了kSecMatchLimit 时并设置为kSecMatchLimitAll会返回所有的，SecItemCopyMatching第二个参数为CFArrayRef，元素为CFDataRef。

更新数据：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");
        }
    }
}

删除钥匙串：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(@"删除成功!!!");
        }
    }
}

总结：钥匙串使用感觉还是挺有用的，今天特意研究了一下，还有两个同一个开发者发布的app之间可以共享钥匙串数据，Sharing Keychain Data Between Multiple Apps，下次有时间研究一下，下次再更新。
简单demo：https://github.com/jiangtaidi/KeyChainPro.git