为PKCS7签名CMS添加签名时间？

Question

我正在尝试将签名时间属性添加到使用SignedCMS签名的文件中。

private byte[] signFile(byte[] fileContent, X509Certificate2 verificationCert) 
{ 
    ContentInfo contentInfo = new ContentInfo(fileContent); 

    SignedCms signedCMS = new SignedCms(contentInfo); 

    CmsSigner cmsSigner = new CmsSigner(SubjectIdentifierType.IssuerAndSerialNumber, verificationCert); 

    Oid signedDate = new Oid("1.2.840.113549.1.9.5"); //oid for PKCS #9 signing time 

    signedDate.Value = DateTime.Now.ToString(); 

    CryptographicAttributeObject cryptoAtty = new CryptographicAttributeObject(signedDate); 

    cmsSigner.SignedAttributes.Add(cryptoAtty); 

    signedCMS.ComputeSignature(cmsSigner, false); 

    byte[] encoded = signedCMS.Encode(); 

    return encoded; 
} 

会发生错误的编码：

CryptographicException: The object identifier is poorly formatted. 

如何正确添加签约时间任何想法？我想我可能必须将签名时间转换为ASN.1编码对象，并将其添加到cryptoAtty的值。如何将日期/时间转换为ASN.1编码对象？

Answer 1

那么这很容易。

cmsSigner.SignedAttributes.Add(new Pkcs9SigningTime());