cipher.getAuthTag()

• 返回：<Buffer> 当使用经过身份验证的加密模式（目前支持 GCM、CCM、OCB 和 chacha20-poly1305）时，cipher.getAuthTag() 方法返回一个 Buffer，其中包含根据给定数据计算出的身份验证标记。

  ¥Returns: <Buffer> When using an authenticated encryption mode (GCM, CCM, OCB, and chacha20-poly1305 are currently supported), the cipher.getAuthTag() method returns a Buffer containing the authentication tag that has been computed from the given data.

只有在使用 cipher.final() 方法完成加密后才应调用 cipher.getAuthTag() 方法。

¥The cipher.getAuthTag() method should only be called after encryption has been completed using the cipher.final() method.

如果在创建 cipher 实例时设置了 authTagLength 选项，则此函数将准确返回 authTagLength 个字节。

¥If the authTagLength option was set during the cipher instance's creation, this function will return exactly authTagLength bytes.