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SignedCms Class

.NET Framework 4

The SignedCms class enables signing and verifying of CMS/PKCS #7 messages.

System.Object
  System.Security.Cryptography.Pkcs.SignedCms

Namespace:  System.Security.Cryptography.Pkcs
Assembly:  System.Security (in System.Security.dll)
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[HostProtectionAttribute(SecurityAction.LinkDemand, MayLeakOnAbort = true)]
public sealed class SignedCms

The SignedCms type exposes the following members.

  Name Description
Public method SignedCms The SignedCms constructor creates an instance of the SignedCms class.
Public method SignedCms(ContentInfo) The SignedCms(ContentInfo) constructor creates an instance of the SignedCms class by using the specified content information as the inner content.
Public method SignedCms(SubjectIdentifierType) The SignedCms(SubjectIdentifierType) constructor creates an instance of the SignedCms class by using the specified subject identifier type as the default subject identifier type for signers.
Public method SignedCms(ContentInfo, Boolean) The SignedCms(ContentInfo, Boolean) constructor creates an instance of the SignedCms class by using the specified content information as the inner content and by using the detached state.
Public method SignedCms(SubjectIdentifierType, ContentInfo) The SignedCms(SubjectIdentifierType, ContentInfo) constructor creates an instance of the SignedCms class by using the specified subject identifier type as the default subject identifier type for signers and content information as the inner content.
Public method SignedCms(SubjectIdentifierType, ContentInfo, Boolean) The SignedCms(SubjectIdentifierType, ContentInfo, Boolean) constructor creates an instance of the SignedCms class by using the specified subject identifier type as the default subject identifier type for signers, the content information as the inner content, and by using the detached state.
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  Name Description
Public property Certificates The Certificates property retrieves the certificates associated with the encoded CMS/PKCS #7 message.
Public property ContentInfo The ContentInfo property retrieves the inner contents of the encoded CMS/PKCS #7 message.
Public property Detached The Detached property retrieves whether the SignedCms object is for a detached signature.
Public property SignerInfos The SignerInfos property retrieves the SignerInfoCollection collection associated with the CMS/PKCS #7 message.
Public property Version The Version property retrieves the version of the CMS/PKCS #7 message.
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  Name Description
Public method CheckHash The CheckHash method verifies the data integrity of the CMS/PKCS #7 message. CheckHash is a specialized method used in specific security infrastructure applications that only wish to check the hash of the CMS message, rather than perform a full digital signature verification. CheckHash does not authenticate the author nor sender of the message because this method does not involve verifying a digital signature. For general-purpose checking of the integrity and authenticity of a CMS/PKCS #7 message, use the CheckSignature(Boolean) or CheckSignature(X509Certificate2Collection, Boolean) methods.
Public method CheckSignature(Boolean) The CheckSignature(Boolean) method verifies the digital signatures on the signed CMS/PKCS #7 message and, optionally, validates the signers' certificates.
Public method CheckSignature(X509Certificate2Collection, Boolean) The CheckSignature(X509Certificate2Collection, Boolean) method verifies the digital signatures on the signed CMS/PKCS #7 message by using the specified collection of certificates and, optionally, validates the signers' certificates.
Public method ComputeSignature The ComputeSignature method prompts the user to select a signing certificate, creates a signature, and adds the signature to the CMS/PKCS #7 message.
Public method ComputeSignature(CmsSigner) The ComputeSignature(CmsSigner) method creates a signature using the specified signer and adds the signature to the CMS/PKCS #7 message.
Public method ComputeSignature(CmsSigner, Boolean) Creates a signature using the specified signer and adds the signature to the CMS/PKCS #7 message. If the value of the silent parameter is false and the Certificate property of the CmsSigner object specified by the signer parameter is not set to a valid certificate, this method prompts the user to select a signing certificate.
Public method Decode The Decode method decodes an encoded SignedCms message. Upon successful decoding, the decoded information can be retrieved from the properties of the SignedCms object.
Public method Encode The Encode method encodes the information in the object into a CMS/PKCS #7 message.
Public method Equals(Object) Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected method Finalize Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public method GetHashCode Serves as a hash function for a particular type. (Inherited from Object.)
Public method GetType Gets the Type of the current instance. (Inherited from Object.)
Protected method MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Public method RemoveSignature(Int32) Removes the signature at the specified index of the SignerInfos collection.
Public method RemoveSignature(SignerInfo) The RemoveSignature method removes the signature for the specified SignerInfo object.
Public method ToString Returns a string that represents the current object. (Inherited from Object.)
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The Cryptographic Message Syntax RFC specifies the following MIME types and file name extensions for CMS/PKCS #7 messages with these content types.

Content type

MIME type

Extension

envelopedData

application/pkcs7-mime

.p7m

signedData

application/pkcs7-signature

.p7s.p7c
Note Note

The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: MayLeakOnAbort. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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How to create only PKCS#7 rather than a CMS?
Hi,

In the above document PKCS#7 and CMS is used interchangeably. I know that there are some minor differences between PKCS#7 and CMS and for that reason I might have to create a pure PKCS#7 rather a CMS. I couldn't figure out how to create one using SignedCms, couldn't find the param for any function for that. Reason is that there could be clients who can only parse PKCS#7 so using SignedCms will break their code as SignedCms is churning out CMS and not a PKCS#7.

Is it possible to create PKCS#7 using SignedCms or I have to rely on other 3rd party crypto toolkits lik Bouncy Castle?
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