Add Signing Time to PKCS7 Signed CMS?

c#, content-management-system, pkcs#7, security, signing

Solution

Well that was easy.

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

Problem

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; } ``` Error thrown on Encode: ``` CryptographicException: The object identifier is poorly formatted. ``` 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?

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