keychain的使用

通常情况下，我们用NSUserDefaults存储数据信息，但是对于一些私密信息，比如密码、证书等等，就需要使用更为安全的keychain了。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后依然有效，数据还在。

使用苹果官方发布的KeychainItemWrapper或者SFHFKeychainUtils很方便，后来看到 iphone使用keychain来存取用户名和密码 一文，觉得对了解keychain有很大的帮助，于是ARC控也尝试了一把。

需要导入Security.framework 

@implementation WQKeyChain  
+ (NSMutableDictionary *)getKeychainQuery:(NSString *)service {  
return [NSMutableDictionary dictionaryWithObjectsAndKeys:  
        (__bridge_transfer id)kSecClassGenericPassword,(__bridge_transfer id)kSecClass,  
        service, (__bridge_transfer id)kSecAttrService,  
        service, (__bridge_transfer id)kSecAttrAccount,  
        (__bridge_transfer id)kSecAttrAccessibleAfterFirstUnlock,(__bridge_transfer 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((__bridge_retained CFDictionaryRef)keychainQuery);  
    //Add new object to search dictionary(Attention:the data format)  
    [keychainQuery setObject:[NSKeyedArchiver archivedDataWithRootObject:data] forKey:(__bridge_transfer id)kSecValueData];  
    //Add item to keychain with the search dictionary  
    SecItemAdd((__bridge_retained CFDictionaryRef)keychainQuery, NULL);  
}  
  
+ (id)load:(NSString *)service {  
    id ret = nil;  
    NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];  
    //Configure the search setting  
    [keychainQuery setObject:(id)kCFBooleanTrue forKey:(__bridge_transfer id)kSecReturnData];  
    [keychainQuery setObject:(__bridge_transfer id)kSecMatchLimitOne forKey:(__bridge_transfer id)kSecMatchLimit];  
    CFDataRef keyData = NULL;  
    if (SecItemCopyMatching((__bridge_retained CFDictionaryRef)keychainQuery, (CFTypeRef *)&keyData) == noErr) {  
        @try {  
            ret = [NSKeyedUnarchiver unarchiveObjectWithData:(__bridge_transfer NSData *)keyData];  
        } @catch (NSException *e) {  
            NSLog(@"Unarchive of %@ failed: %@", service, e);  
        } @finally {  
        }  
    }  
    return ret;  
}  
  
+ (void)delete:(NSString *)service {  
    NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];  
    SecItemDelete((__bridge_retained CFDictionaryRef)keychainQuery);  
}  
@end  

比如，保存密码

@interface WQUserDataManager : NSObject  
  
/** 
 *  @brief  存储密码 
 * 
 *  @param  password    密码内容 
 */  
+(void)savePassWord:(NSString *)password;  
  
/** 
 *  @brief  读取密码 
 * 
 *  @return 密码内容 
 */  
+(id)readPassWord;  
  
/** 
 *  @brief  删除密码数据 
 */  
+(void)deletePassWord;  
  
@end 

#import "WQUserDataManager.h"  
  
@implementation WQUserDataManager  
  
static NSString * const KEY_IN_KEYCHAIN = @"com.wuqian.app.allinfo";  
static NSString * const KEY_PASSWORD = @"com.wuqian.app.password";  
  
+(void)savePassWord:(NSString *)password  
{  
    NSMutableDictionary *usernamepasswordKVPairs = [NSMutableDictionary dictionary];  
    [usernamepasswordKVPairs setObject:password forKey:KEY_PASSWORD];  
    [WQKeyChain save:KEY_IN_KEYCHAIN data:usernamepasswordKVPairs];  
}  
  
+(id)readPassWord  
{  
    NSMutableDictionary *usernamepasswordKVPair = (NSMutableDictionary *)[WQKeyChain load:KEY_IN_KEYCHAIN];  
    return [usernamepasswordKVPair objectForKey:KEY_PASSWORD];  
}  
  
+(void)deletePassWord  
{  
    [WQKeyChain delete:KEY_IN_KEYCHAIN];  
}  
@end