向PKCS7签名的CMS添加签名时间？ [英] Add Signing Time to PKCS7 Signed CMS?

问题描述

我正在尝试添加签名时间属性到我使用SignedCMS签名的文件。

I'm trying to add the signing time attribute to a file that I am signing using SignedCMS.

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;
}

Encode上抛出的错误：

Error thrown on Encode:

CryptographicException: The object identifier is poorly formatted. 

有关如何正确添加签名时间的任何想法？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？

Any ideas on how to properly add the signing time? I think I may have to convert the signing time to an ASN.1 encoded object and add that to cryptoAtty's values. How would one convert the date/time to an ASN.1 Encoded object?

推荐答案

很容易。

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

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