CmsInformation Class

This class represents the CMS information used to sign a PDF document.

Inheritance Hierarchy

SystemObject
Atalasoft.PdfDoc.DigitalSignaturesCmsInformation

Namespace: Atalasoft.PdfDoc.DigitalSignatures
Assembly: Atalasoft.PdfDoc (in Atalasoft.PdfDoc.dll) Version: 11.4.0.9.0.377 (.NET 4.5.2, x86)

Syntax

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public class CmsInformation

Public Class CmsInformation

The CmsInformation type exposes the following members.

Constructors

	Name	Description
	CmsInformation(X509Certificate2Collection)	Initializes a new instance of the CmsInformation class.
	CmsInformation(X509Certificate2Collection, PdfContentDigestMethod, UnsupportedContentDigestAlgorithmAction)	Initializes a new instance of the CmsInformation class.
	CmsInformation(Stream, SecureString, PdfContentDigestMethod, UnsupportedContentDigestAlgorithmAction)	Initializes a new instance of the CmsInformation class.

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Properties

	Name	Description
	Certificates	Gets the certificates collection. This represents the certificate or chain of certificates used to sign the document. The actual signer will always be the first.
	ContentDigestMethod	Gets the content digest method that will be used to create a message digest of the PDF file. Note that this is currently only used for signature creation and not for reflecting the method used in a signed file.
	ContentDigestMethodIsSupported	Gets a value indicating whether the ContentDigestMethod is supported by the provided certificate if it is supported, it will be used as is. If it is unsupported, at the time of saving the document (in PdfDocument or PdfGeneratedDocument) or signing (in PdfDocumentSigner), the UnsupportedContentDigestAlgorithmAction will be invoked.
	UnsupportedContentDigestAlgorithmAction	Gets the action that will be taken when the ContentDigestMethod is not supported.

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Methods

	Name	Description
	Equals	Determines whether the specified object is equal to the current object. (Inherited from Object.)
	Finalize	Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
	GetHashCode	Serves as the default hash function. (Inherited from Object.)
	GetType	Gets the Type of the current instance. (Inherited from Object.)
	MemberwiseClone	Creates a shallow copy of the current Object. (Inherited from Object.)
	ToString	Returns a string that represents the current object. (Inherited from Object.)

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Remarks

When a PDF document is signed, the X509Certificate2Collection is used to create a cryptographic signature that will be embedded in the PDF file. If the certificate uses RSA encryption and the RSACryptoServiceProvider object in the certificate does not support the specified digest algorithm, DotPdf will attempt to use BouncyCastle to perform the signing. This will only work as a fall back method if the certificate came from a file and the file was opened as having the private key exportable.

Otherwise, the property ContentDigestMethodIsSupported will be false and at the time of signing, DotPdf will invoke the action in the property UnsupportedContentDigestAlgorithmAction. Almost certainly, certificates that come from the Windows certificate store will NOT have an exportable private key.

Examples

This sample shows how to open a certificate file to allow exporting a private key.

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X509Certificate2 cert = new X509Certificate2(pathToACertFile, yourCertPassword, X509KeyStorageFlags.Exportable);

Examples

How to determine the set of supported digest methods.

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public IList<PdfContentDigestMethod> GetSupportedDigestMethods(X509Certificate2Collection certificates)
{
    List<PdfContentDigestMethod> meths = new List<PdfContentDigestMethod>();
    foreach (PdfContentDigestMethod method in Enum.GetValues(typeof(PdfContentDigestMethod)))
    {
        CmsInformation cms = new CmsInformation(certificate, method, UnsupportedContentDigestAlgorithmAction.FallBackToSHA1);
        if (cms.ContentDigestMethodIsSupported)
            meths.Add(method);
    }
    return meths;
}

Reference

Atalasoft.PdfDoc.DigitalSignatures Namespace