Keychain を NSUserDefaults のように使う

TheLevelUp/LUKeychainAccess · GitHub

こんな感じで使う。

[[LUKeychainAccess standardKeychainAccess] setBool:NO forKey:@"authorized"];
BOOL authorized = [[LUKeychainAccess standardKeychainAccess] boolForKey:@"authorized"];

API

// Public Methods
+ (LUKeychainAccess *)standardKeychainAccess;

// Getters
- (BOOL)boolForKey:(NSString *)key;
- (NSData *)dataForKey:(NSString *)key;
- (double)doubleForKey:(NSString *)key;
- (float)floatForKey:(NSString *)key;
- (NSInteger)integerForKey:(NSString *)key;
- (id)objectForKey:(NSString *)key;
- (NSString *)stringForKey:(NSString *)key;

// Setters
- (void)setBool:(BOOL)value forKey:(NSString *)key;
- (void)setData:(NSData *)data forKey:(NSString *)key;
- (void)setDouble:(double)value forKey:(NSString *)key;
- (void)setFloat:(float)value forKey:(NSString *)key;
- (void)setInteger:(NSInteger)value forKey:(NSString *)key;
- (void)setObject:(id)value forKey:(NSString *)key;
- (void)setString:(NSString *)inputString forKey:(NSString *)key;

Keychain に保管した情報はアプリを削除しても残るのでそれを利用した用途に適していると思われる。

（参考）

Cocoaの日々: [iOS] Keychain Services とは