用keychain（钥匙串）保存用户名和密码

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

+( void)savePassWord:(NSString *)password;

+(id)readPassWord;

+( 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];

}