X509SubjectKeyIdentifierExtension Class

X509SubjectKeyIdentifierExtension Class

 

Defines a string that identifies a certificate's subject key identifier (SKI). This class cannot be inherited.

Namespace:   System.Security.Cryptography.X509Certificates
Assembly:  System (in System.dll)

System.Object
  System.Security.Cryptography.AsnEncodedData
    System.Security.Cryptography.X509Certificates.X509Extension
      System.Security.Cryptography.X509Certificates.X509SubjectKeyIdentifierExtension

public sealed class X509SubjectKeyIdentifierExtension : X509Extension

NameDescription
System_CAPS_pubmethodX509SubjectKeyIdentifierExtension()

Initializes a new instance of the X509SubjectKeyIdentifierExtension class.

System_CAPS_pubmethodX509SubjectKeyIdentifierExtension(AsnEncodedData, Boolean)

Initializes a new instance of the X509SubjectKeyIdentifierExtension class using encoded data and a value that identifies whether the extension is critical.

System_CAPS_pubmethodX509SubjectKeyIdentifierExtension(Byte[], Boolean)

Initializes a new instance of the X509SubjectKeyIdentifierExtension class using a byte array and a value that identifies whether the extension is critical.

System_CAPS_pubmethodX509SubjectKeyIdentifierExtension(PublicKey, Boolean)

Initializes a new instance of the X509SubjectKeyIdentifierExtension class using a public key and a value indicating whether the extension is critical.

System_CAPS_pubmethodX509SubjectKeyIdentifierExtension(PublicKey, X509SubjectKeyIdentifierHashAlgorithm, Boolean)

Initializes a new instance of the X509SubjectKeyIdentifierExtension class using a public key, a hash algorithm identifier, and a value indicating whether the extension is critical.

System_CAPS_pubmethodX509SubjectKeyIdentifierExtension(String, Boolean)

Initializes a new instance of the X509SubjectKeyIdentifierExtension class using a string and a value that identifies whether the extension is critical.

NameDescription
System_CAPS_pubpropertyCritical

Gets a Boolean value indicating whether the extension is critical.(Inherited from X509Extension.)

System_CAPS_pubpropertyOid

Gets or sets the Oid value for an AsnEncodedData object.(Inherited from AsnEncodedData.)

System_CAPS_pubpropertyRawData

Gets or sets the Abstract Syntax Notation One (ASN.1)-encoded data represented in a byte array.(Inherited from AsnEncodedData.)

System_CAPS_pubpropertySubjectKeyIdentifier

Gets a string that represents the subject key identifier (SKI) for a certificate.

NameDescription
System_CAPS_pubmethodCopyFrom(AsnEncodedData)

Creates a new instance of the X509SubjectKeyIdentifierExtension class by copying information from encoded data.(Overrides X509Extension.CopyFrom(AsnEncodedData).)

System_CAPS_pubmethodEquals(Object)

Determines whether the specified object is equal to the current object.(Inherited from Object.)

System_CAPS_pubmethodFormat(Boolean)

Returns a formatted version of the Abstract Syntax Notation One (ASN.1)-encoded data as a string.(Inherited from AsnEncodedData.)

System_CAPS_pubmethodGetHashCode()

Serves as the default hash function. (Inherited from Object.)

System_CAPS_pubmethodGetType()

Gets the Type of the current instance.(Inherited from Object.)

System_CAPS_pubmethodToString()

Returns a string that represents the current object.(Inherited from Object.)

There are several ways to identify a certificate: by the hash of the certificate, by the issuer and serial number, and by the subject key identifier (SKI). The SKI provides a unique identification for the certificate's subject and is often used when working with XML digital signing.

The following code example demonstrates how to open a user’s personal certificate store and display information about each certificate in the store. This example uses the X509SubjectKeyIdentifierExtension class to display the information.

using System;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;

public class CertSelect
{
    public static void Main()
    {
        try
        {
            X509Store store = new X509Store("MY", StoreLocation.CurrentUser);
            store.Open(OpenFlags.ReadOnly | OpenFlags.OpenExistingOnly);

            X509Certificate2Collection collection = (X509Certificate2Collection)store.Certificates;
            for (int i = 0; i < collection.Count; i++)
            {
                foreach (X509Extension extension in collection[i].Extensions)
                {
                    Console.WriteLine(extension.Oid.FriendlyName + "(" + extension.Oid.Value + ")");


                    if (extension.Oid.FriendlyName == "Key Usage")
                    {
                        X509KeyUsageExtension ext = (X509KeyUsageExtension)extension;
                        Console.WriteLine(ext.KeyUsages);
                    }

                    if (extension.Oid.FriendlyName == "Basic Constraints")
                    {
                        X509BasicConstraintsExtension ext = (X509BasicConstraintsExtension)extension;
                        Console.WriteLine(ext.CertificateAuthority);
                        Console.WriteLine(ext.HasPathLengthConstraint);
                        Console.WriteLine(ext.PathLengthConstraint);
                    }

                    if (extension.Oid.FriendlyName == "Subject Key Identifier")
                    {
                        X509SubjectKeyIdentifierExtension ext = (X509SubjectKeyIdentifierExtension)extension;
                        Console.WriteLine(ext.SubjectKeyIdentifier);
                    }

                    if (extension.Oid.FriendlyName == "Enhanced Key Usage")
                    {
                        X509EnhancedKeyUsageExtension ext = (X509EnhancedKeyUsageExtension)extension;
                        OidCollection oids = ext.EnhancedKeyUsages;
                        foreach (Oid oid in oids)
                        {
                            Console.WriteLine(oid.FriendlyName + "(" + oid.Value + ")");
                        }
                    }
                }
            }
            store.Close();
        }
        catch (CryptographicException)
        {
            Console.WriteLine("Information could not be written out for this certificate.");
        }
    }
}

Universal Windows Platform
Available since 10
.NET Framework
Available since 2.0

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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