HarmonyOS 获取18位随机数没有生效

参考代码：

let random18Str = ''
   //取18位随机数
   let rand = cryptoFramework.createRandom();
   try {
     let randData = rand.generateRandomSync(18);
     if (randData != null) {
       random18Str = randData.data.toString()
       console.info('[Sync]: rand result: ' + randData.data);
     } else {
       console.error("[Sync]: get rand result fail!");
     }
   } catch (error) {
     let e: BusinessError = error as BusinessError;
     console.error(`sync error, ${e.code}, ${e.message}`);
   }
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