• 现在很多人对于安全越来越重视，作为程序猿的我们，也需要在这一方面多下功夫，让我们APP用户储存的私人信息更加的安全，我看到过很多的人写代码，虽然明文密码不会被储存，经常是储存服务器返回的一个秘钥，大部分程序猿就裸存了，直接就存储在NSUserDefaults里面了，也有些程序猿有对其进行AES或DES加密后再储存，但是其本身AES或DES的秘钥都是写在代码中的，一旦程序被反编译，想要获取的秘钥也是相当容易的一件事了。

• 苹果自己本身就有一个方法可以让我们储存一些机密的东西，储存的机制就是将我们需要储存的东西储存在钥匙串🔑里面，这样除非整个iOS的安全机制被破解，要不然你储存的东西就会相对的安全。

下面提供一个工具类KeychainTool用户存储

• KeychainTool.h

#import <Foundation/Foundation.h>

@interface KeychainTool : NSObject

/**
 *  储存字符串到🔑钥匙串
 *
 *  @param sValue 对应的Value
 *  @param sKey   对应的Key
 */
+ (void)saveKeychainValue:(NSString *)sValue Key:(NSString *)sKey;

/**
 *  从🔑钥匙串获取字符串
 *
 *  @param sKey 对应的Key
 *
 *  @return 返回储存的Value
 */
+ (NSString *)readKeychainValue:(NSString *)sKey;

/**
 *  从🔑钥匙串删除字符串
 *
 *  @param sKey 对应的Key
 */
+ (void)deleteKeychainValue:(NSString *)sKey;

@end

• KeychainTool.m

#import "KeychainTool.h"

@implementation KeychainTool

+ (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)saveKeychainValue:(NSString *)sValue Key:(NSString *)sKey
{
    //Get search dictionary
    NSMutableDictionary *keychainQuery = [self getKeychainQuery:sKey];
    //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:sValue] forKey:(__bridge_transfer id)kSecValueData];
    //Add item to keychain with the search dictionary
    SecItemAdd((__bridge_retained CFDictionaryRef)keychainQuery, NULL);
}

+ (NSString *)readKeychainValue:(NSString *)sKey
{
    NSString *ret = nil;
    NSMutableDictionary *keychainQuery = [self getKeychainQuery:sKey];
    
    //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 = (NSString *)[NSKeyedUnarchiver unarchiveObjectWithData:(__bridge_transfer NSData *)keyData];
        } @catch (NSException *e) {
            NSLog(@"Unarchive of %@ failed: %@", sKey, e);
        } @finally {
        }
    }
    return ret;
}


+ (void)deleteKeychainValue:(NSString *)sKey {
    NSMutableDictionary *keychainQuery = [self getKeychainQuery:sKey];
    SecItemDelete((__bridge_retained CFDictionaryRef)keychainQuery);
}

@end