iOS开发——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

实现一个简单的界面，把设定的密码存起来，然后立即读取显示出来看看效果

 -(IBAction)btnAciton:(id)sender
 {
     [WQUserDataManager savePassWord:self.textfield.text];
     self.label.text = [WQUserDataManager readPassWord];
 }

达到了预期的效果。