iOS 使用KeyChain保存数据

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一般情况下，可以用NSUserDefaults存储数据信息，但是对于一些私密信息，比如账号、密码等等，就需要使用更为安全的keychain了。而Keychain的信息是存在于每个应用（app）的沙盒之外的，所以keychain里保存的信息不会因App被删除而丢失，在用户重新安装App后数据还在。

新建一个类，取名JJKeyChain，如下：

#import <Foundation/Foundation.h>#import <Security/Security.h>#define KEY_PASSWORD  @"com.rry.app.password"#define KEY_USERNAME_PASSWORD  @"com.rry.app.usernamepassword"@interface JJKeyChain : NSObject+ (void)save:(NSString *)service data:(id)data;+ (id)load:(NSString *)service;+ (void)delete:(NSString *)service;@end

.m文件里代码:

+ (NSMutableDictionary *)getKeychainQuery:(NSString *)service {    return [NSMutableDictionary dictionaryWithObjectsAndKeys:            (id)kSecClassGenericPassword,(id)kSecClass,            service, (id)kSecAttrService,            service, (id)kSecAttrAccount,            (id)kSecAttrAccessibleAfterFirstUnlock,(id)kSecAttrAccessible,            nil];}+ (void)save:(NSString *)service data:(id)data {    //Get search dictionary    NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];    //Delete old item before add new item    SecItemDelete((CFDictionaryRef)keychainQuery);    //Add new object to search dictionary(Attention:the data format)    [keychainQuery setObject:[NSKeyedArchiver archivedDataWithRootObject:data] forKey:(id)kSecValueData];    //Add item to keychain with the search dictionary    SecItemAdd((CFDictionaryRef)keychainQuery, NULL);}+ (id)load:(NSString *)service {    id ret = nil;    NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];    //Configure the search setting    //Since in our simple case we are expecting only a single attribute to be returned (the password) we can set the attribute kSecReturnData to kCFBooleanTrue    [keychainQuery setObject:(id)kCFBooleanTrue forKey:(id)kSecReturnData];    [keychainQuery setObject:(id)kSecMatchLimitOne forKey:(id)kSecMatchLimit];    CFDataRef keyData = NULL;    if (SecItemCopyMatching((CFDictionaryRef)keychainQuery, (CFTypeRef *)&keyData) == noErr) {        @try {            ret = [NSKeyedUnarchiver unarchiveObjectWithData:(__bridge NSData *)keyData];        } @catch (NSException *e) {            NSLog(@"Unarchive of %@ failed: %@", service, e);        } @finally {        }    }    if (keyData)        CFRelease(keyData);    return ret;}+ (void)delete:(NSString *)service {    NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];    SecItemDelete((CFDictionaryRef)keychainQuery);}

使用示例:

    //存    NSMutableDictionary *usernamepasswordKVPairs = [NSMutableDictionary dictionary];    [usernamepasswordKVPairs setObject:@"123" forKey:KEY_PASSWORD];    [JJKeyChain save:KEY_USERNAME_PASSWORD data:usernamepasswordKVPairs];        //取    NSMutableDictionary *usernamepasswordKVPairs1 = (NSMutableDictionary *)[JJKeyChain load:KEY_USERNAME_PASSWORD];        NSLog(@"%@",[usernamepasswordKVPairs1 objectForKey:KEY_PASSWORD]);            //删    [JJKeyChain delete:KEY_USERNAME_PASSWORD];

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