iOS UUID配合keychain的替换方案实现

iOS的keychain服务提供了一种安全的保存私密信息（密码，序列号，证书等）的方式，每个iOS程序都有一个独立的keychain存储。相对于NSUserDefaults、文件保存等一般方式，keychain保存更为安全，而且keychain里保存的信息不会因App被删除而丢失，所以在重装App后，keychain里的数据还能使用。

在应用里使用使用keyChain，我们需要导入Security.framework

要先声明公共区的名称，官方文档管这个名称叫“keychain access group”，声明的方法是新建一个plist文件，名字随便起，内容如下：

“yourAppID.com.yourCompany.whatever”就是你要起的公共区名称

获取UUID 并保存到keychain中：

#pragma mark--获取设备UUID
-(NSString*) uuid {
    
    if ([CHKeychain load:UUIDKEY]) {
         
         NSString *result = [CHKeychain load:UUIDKEY];
         
        return result;
    }
    else
    {
        CFUUIDRef puuid = CFUUIDCreate( nil );
        CFStringRef uuidString = CFUUIDCreateString( nil, puuid );
        NSString * result = (NSString *)CFStringCreateCopy( NULL, uuidString);
        CFRelease(puuid);
        CFRelease(uuidString);
         
        [CHKeychain save:UUIDKEY data:result];
         
        return [result autorelease];
    }
     
  
    return nil;
}

CHKeychain 的实现代码（需要导入Security.framework）：

CHKeychain.h

#import <Foundation/Foundation.h>
 
@interface CHKeychain : NSObject
 
+ (void)save:(NSString *)service data:(id)data;
+ (id)load:(NSString *)service;
+ (void)deleteData:(NSString *)service;
 
 
@end

CHKeychain.m　　

#import "CHKeychain.h"
 
@implementation CHKeychain
+ (NSMutableDictionary *)getKeychainQuery:(NSString *)service {
    return [NSMutableDictionary dictionaryWithObjectsAndKeys:
            (id)kSecClassGenericPassword,(id)kSecClass,
            service, (id)kSecAttrService,
            service, (id)kSecAttrAccount,
            (id)kSecAttrAccessibleAfterFirstUnlock,(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((CFDictionaryRef)keychainQuery);
    //Add new object to search dictionary(Attention:the data format)
    [keychainQuery setObject:[NSKeyedArchiver archivedDataWithRootObject:data] forKey:(id)kSecValueData];
    //Add item to keychain with the search dictionary
    SecItemAdd((CFDictionaryRef)keychainQuery, NULL);
}
 
+ (id)load:(NSString *)service {
    id ret = nil;
    NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];
    //Configure the search setting
    //Since in our simple case we are expecting only a single attribute to be returned (the password) we can set the attribute kSecReturnData to kCFBooleanTrue
    [keychainQuery setObject:(id)kCFBooleanTrue forKey:(id)kSecReturnData];
    [keychainQuery setObject:(id)kSecMatchLimitOne forKey:(id)kSecMatchLimit];
    CFDataRef keyData = NULL;
    if (SecItemCopyMatching((CFDictionaryRef)keychainQuery, (CFTypeRef *)&keyData) == noErr) {
        @try {
            ret = [NSKeyedUnarchiver unarchiveObjectWithData:(NSData *)keyData];
        } @catch (NSException *e) {
            NSLog(@"Unarchive of %@ failed: %@", service, e);
        } @finally {
        }
    }
    if (keyData)
        CFRelease(keyData);
    return ret;
}
 
+ (void)delete:(NSString *)service {
    NSMutableDictionary *keychainQuery = [self getKeychainQuery:service];
    SecItemDelete((CFDictionaryRef)keychainQuery);
}
 
@end