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AssemblySignatureKeyAttribute Class

.NET Framework 4.6 and 4.5

Provides migration from an older, simpler strong name key to a larger key with a stronger hashing algorithm.


Namespace:  System.Reflection
Assembly:  mscorlib (in mscorlib.dll)

[AttributeUsageAttribute(AttributeTargets.Assembly, Inherited = false, AllowMultiple = false)]
public sealed class AssemblySignatureKeyAttribute : Attribute

The AssemblySignatureKeyAttribute type exposes the following members.

Public methodAssemblySignatureKeyAttributeCreates a new instance of the AssemblySignatureKeyAttribute class by using the specified public key and countersignature.

Public propertyCountersignatureGets the countersignature for the strong name for this assembly.
Public propertyPublicKeyGets the public key for the strong name used to sign the assembly.
Public propertyTypeIdWhen implemented in a derived class, gets a unique identifier for this Attribute. (Inherited from Attribute.)

Public methodEqualsInfrastructure. Returns a value that indicates whether this instance is equal to a specified object. (Inherited from Attribute.)
Public methodGetHashCodeReturns the hash code for this instance. (Inherited from Attribute.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodIsDefaultAttributeWhen overridden in a derived class, indicates whether the value of this instance is the default value for the derived class. (Inherited from Attribute.)
Public methodMatchWhen overridden in a derived class, returns a value that indicates whether this instance equals a specified object. (Inherited from Attribute.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)

Explicit interface implemetationPrivate method_Attribute.GetIDsOfNamesMaps a set of names to a corresponding set of dispatch identifiers. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoRetrieves the type information for an object, which can be used to get the type information for an interface. (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.GetTypeInfoCountRetrieves the number of type information interfaces that an object provides (either 0 or 1). (Inherited from Attribute.)
Explicit interface implemetationPrivate method_Attribute.InvokeProvides access to properties and methods exposed by an object. (Inherited from Attribute.)

The new larger key is the signature key. In versions before the .NET Framework 4.5, the signature key was identical to the identity key. Starting with the .NET Framework 4.5, the AssemblySignatureKeyAttribute attribute allows the assembly metadata to continue to have the old public key token and binary large object (BLOB) so that existing assembly references continue to work. It also ensures that the mapping comes from an owner of the identity key.

The presence of the attribute does not necessarily mean that strong name validation takes place. In common full-trust scenarios, the attribute is never considered, because strong name signatures are never validated. However, when the strong name signature does have to be validated, both the strong name signature and the countersignature must be validated. The assembly’s identity key does not have to be identical to the signature key (the key used to do the actual signing and validation). The identity key can be mapped to a different (more robust) signing key. This lets you set the identity of an assembly, and update the signing keys and algorithms to more secure versions.

The countersignature addresses security concerns when a malicious assembly claims some other identity. For example, a malicious System.Core.dll assembly could contain the Microsoft public key in its metadata, and use the attribute to tell strong name validation to use the attacker’s signature key if no countersignature is present. Thus, it could masquerade as a strong name-validated Microsoft assembly.

For information about how to sign assemblies for use with this new attribute, see Enhanced Strong Naming.

.NET Framework

Supported in: 4.6, 4.5

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
© 2015 Microsoft