SFHFKeychainUtils （下载地址 https://github.com/ldandersen/scifihifi-iphone）是一个封装了KeyChain简单操作的第三方类库
1、引入Security.frameWork框架。

2、引入头文件：SFHKeychainUtils.h.（注意：SFHKeychainUtils为MRC，在ARC环境需配置如下）

3、方法如下

pragma mark -获取唯一UUID

• (NSString*)UUID {

  NSDictionary *infoDict = [[NSBundle mainBundle] infoDictionary];

  NSString *userName = infoDict[@"CFBundleName"];

  NSString *serviceName = infoDict[@"CFBundleIdentifier"];

  NSString *UUID = [SFHFKeychainUtils getPasswordForUsername:userName andServiceName:serviceName error:nil];

  if (UUID.length==0) {

      UUID = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
  
      [SFHFKeychainUtils storeUsername:userName andPassword:UUID forServiceName:serviceName updateExisting:1 error:nil];
  }
  returnUUID;
  

}