在C#中对文件进行数字签名时如何添加时间戳？

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

public class FileSignature
{
    public static void SignFile(string filePath, string privateKey)
    {
        // 读取文件内容
        byte[] fileContent = File.ReadAllBytes(filePath);

        // 获取当前时间戳
        byte[] timestamp = BitConverter.GetBytes(DateTime.UtcNow.ToBinary());

        // 合并文件内容和时间戳
        byte[] dataToSign = new byte[fileContent.Length + timestamp.Length];
        Buffer.BlockCopy(fileContent, 0, dataToSign, 0, fileContent.Length);
        Buffer.BlockCopy(timestamp, 0, dataToSign, fileContent.Length, timestamp.Length);

        // 使用私钥对数据进行签名
        RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
        rsa.FromXmlString(privateKey);
        byte[] signature = rsa.SignData(dataToSign, CryptoConfig.MapNameToOID("SHA256"));

        // 将签名数据写入文件
        using (FileStream fs = new FileStream(filePath + ".sig", FileMode.Create))
        {
            fs.Write(signature, 0, signature.Length);
        }
    }

    public static bool VerifyFile(string filePath, string publicKey)
    {
        // 读取文件内容和签名数据
        byte[] fileContent = File.ReadAllBytes(filePath);
        byte[] signature = File.ReadAllBytes(filePath + ".sig");

        // 获取当前时间戳
        byte[] timestamp = BitConverter.GetBytes(DateTime.UtcNow.ToBinary());

        // 合并文件内容和时间戳
        byte[] dataToVerify = new byte[fileContent.Length + timestamp.Length];
        Buffer.BlockCopy(fileContent, 0, dataToVerify, 0, fileContent.Length);
        Buffer.BlockCopy(timestamp, 0, dataToVerify, fileContent.Length, timestamp.Length);

        // 使用公钥验证签名
        RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
        rsa.FromXmlString(publicKey);
        return rsa.VerifyData(dataToVerify, CryptoConfig.MapNameToOID("SHA256"), signature);
    }
}