AuthenticateAsServer Method (ExtendedProtectionPolicy)

NegotiateStream.AuthenticateAsServer Method (ExtendedProtectionPolicy)


Called by servers to authenticate the client, and optionally the server, in a client-server connection. The authentication process uses the specified extended protection policy.

Namespace:   System.Net.Security
Assembly:  System (in System.dll)

public virtual void AuthenticateAsServer(
	ExtendedProtectionPolicy policy


Type: System.Security.Authentication.ExtendedProtection.ExtendedProtectionPolicy

The ExtendedProtectionPolicy that is used for extended protection.

Exception Condition

The CustomChannelBinding and CustomServiceNames on the extended protection policy passed in the policy parameter are both null.


The authentication failed. You can use this object to retry the authentication.


The authentication failed. You can use this object to retry the authentication.


Windows 95 and Windows 98 are not supported.


This object has been closed.


The policy parameter was set to Always on a platform that does not support extended protection.

The authentication uses the server's DefaultCredentials. No Service Principal Name (SPN) is specified for the server. The impersonation level is Identification, and the security level is EncryptAndSign.

If the policy parameter is null, then an extended protection policy is used that has PolicyEnforcement set to Never.

When authentication succeeds, you must check the IsEncrypted and IsSigned properties to determine what security services are used by the NegotiateStream. Check the IsMutuallyAuthenticated property to determine whether mutual authentication occurred.

This method blocks until the operation completes. To prevent blocking until the operation completes, use one of the BeginAuthenticateAsServer method overloads.

If the authentication fails, you receive an AuthenticationException or an InvalidCredentialException. In this case, you can retry the authentication with a different credential.

.NET Framework
Available since 2.0
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