C#

1. The X.509 certificate is not signed with the necessary OIDs that identify the certificate for client and/or server authentication.
2. Since you made this certificate yourself, you most likely used a self-signing certificate authority (CA). You must add the CA to the trusted certificate store for the machine.
3. The ceritifcate is not accessible because you've stored the private key into another user's ceritifcate store (like your local user's or the administrative store), or because the ASPNET user accountcannot access private keys by default and you're not impersonating another user (or running ASP.NET under a different user context).

System.Web.Services.Protocols.SoapHeaderException: Server unavailable, please try later ---> System.ComponentModel.Win32Exception: Bad Key at Microsoft.Web.Services2.Security.Cryptography.RSACryptoServiceProvider.Encrypt(Byte[] plaintext, Boolean useOAEP) at Microsoft.Web.Services2.Security.Cryptography.RSA15KeyExchangeFormatter.EncryptKey(Byte[] plainKey) at Microsoft.Web.Services2.Security.EncryptedKey.Encrypt() at Microsoft.Web.Services2.Security.EncryptedKey.GetXml(XmlDocument document) at Microsoft.Web.Services2.Security.Security.SerializeXml(SoapEnvelope document) at Microsoft.Web.Services2.Security.SecurityOutputFilter.ProcessHeader(Security security, SoapEnvelope envelope) at Microsoft.Web.Services2.Security.SecurityOutputFilter.ProcessMessage(SoapEnvelope envelope) at Microsoft.Web.Services2.Pipeline.ProcessOutputMessage(SoapEnvelope envelope) at Microsoft.Web.Services2.WebServicesExtension.AfterSerializeServer(SoapServerMessage message) --- End of inner exception stack trace --- 

SoapHeaderException: System.Web.Services.Protocols.SoapHeaderException: Server unavailable, please try later ---> System.ComponentModel.Win32Exception: Bad Key
   at Microsoft.Web.Services2.Security.Cryptography.RSACryptoServiceProvider.Encrypt(Byte[] plaintext, Boolean useOAEP)
   at Microsoft.Web.Services2.Security.Cryptography.RSA15KeyExchangeFormatter.EncryptKey(Byte[] plainKey)
   at Microsoft.Web.Services2.Security.EncryptedKey.Encrypt()
   at Microsoft.Web.Services2.Security.EncryptedKey.GetXml(XmlDocument document)
   at Microsoft.Web.Services2.Security.Security.SerializeXml(SoapEnvelope document)
   at Microsoft.Web.Services2.Security.SecurityOutputFilter.ProcessHeader(Security security, SoapEnvelope envelope)
   at Microsoft.Web.Services2.Security.SecurityOutputFilter.ProcessMessage(SoapEnvelope envelope)
   at Microsoft.Web.Services2.Pipeline.ProcessOutputMessage(SoapEnvelope envelope)
   at Microsoft.Web.Services2.WebServicesExtension.AfterSerializeServer(SoapServerMessage message)
   --- End of inner exception stack trace ---]
   System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall)
   System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)
   SecureServiceLib.RestekSecureServiceClient2.Invoke(String methodName, Object[] parameters) in c:\projects\securewebservice\secureservicesolution\secureservicelib\clsresteksecureserviceclient2.cs:26
   WSE2Client.localhost.Service2.HelloWorld() in c:\inetpub\wwwroot\WSE2Client\Web References\localhost\Reference.cs:45
   WSE2Client.WebForm1.Page_Load(Object sender, EventArgs e) in c:\inetpub\wwwroot\wse2client\webform1.aspx.cs:24
   System.Web.UI.Control.OnLoad(EventArgs e)
   System.Web.UI.Control.LoadRecursive()
   System.Web.UI.Page.ProcessRequestMain()

protected virtual void AddSignAndEncryptInformation()
{
	_addResponseEncryption();
	_addResponseSignature(); //omitted from this post
}
private void _addResponseEncryption()
{
	SoapContext responseContext = ResponseSoapContext.Current;
	X509SecurityToken e =this.GetResponseEncryptingSecurtyToken ();
	responseContext.Security.Tokens.Add (e);
	responseContext.Security.Elements.Add (new EncryptedData (e));
}
protected virtual X509SecurityToken GetResponseEncryptingSecurtyToken() 
{            
	X509SecurityToken securityToken = null;
	//localmachine
	X509CertificateStore store = X509CertificateStore.LocalMachineStore(X509CertificateStore.MyStore);

	bool open = store.OpenRead();
	try 
	{
		//this is the thumb print of the cert!
		byte[] certHash=this.GetHash ("RestekClient");
		X509CertificateCollection certs =store.FindCertificateByHash (certHash);		

		X509Certificate cert =
					((X509Certificate) certs[0]);

		if (cert != null) 
		{
			securityToken = new X509SecurityToken(cert);
		}
	} 
	finally 
	{
		if (store != null)
			store.Close();
	}
	bool b=	securityToken.Certificate.SupportsDataEncryption ;
	if (b)
	        return securityToken;
	throw new Exception ("Cert does not support data encryption");
}
private byte[] GetHash(string KeyName)
{
	byte[] b=null;
	if (KeyName=="RestekClient")
		b=new byte[] {0xee, 0x2b, 0xba, 0xb4, 0xeb, 0x6d, 0xff, 0x1e, 0xf2, 0xc4, 0x70, 0xf9, 0x10, 0xa5, 0xfd, 0xf4, 0x03, 0xd8, 0xfb, 0xaf};

	if (KeyName=="RestekServer")
		b=new byte[] {0xab, 0xaf, 0xe2, 0x9d, 0xa2, 0x0a, 0xda, 0xd1, 0x02, 0x0d, 0xee, 0x50, 0xf1, 0xf1, 0xb5, 0xc1, 0x22, 0x4c, 0x1d, 0xe3};

	if (KeyName=="WSEQuickStartServer")
		b=new byte[] {0x87, 0xd9, 0x2c, 0xca, 0xb7, 0x14, 0xc3, 0x0d, 0xb0, 0xe0, 0xba, 0xe6, 0xb9, 0xb0, 0xb6, 0x5b, 0x5d, 0x6d, 0xf7, 0xcf};
	return(b);
}

[WebMethod]
public string HelloWorld()
{
	this.AssureCredentialsValid (); //omitted from this post
	this.AddSignAndEncryptInformation ();
	return ("Hello World");
}

[DllImport("qw.dll")]
static extern string ReportVersion(string a);

//#!csc.exe /t:winexe Test.cs
//
 
using System;
using System.Drawing;
using System.Windows.Forms;
 
class Test : Form
{
  static void Main()
  {
    Application.Run(new Test());
  }
 
  TextBox tb;
 
  Test()
  {
    tb = new TextBox();
    Controls.Add(tb);
    tb.Multiline = true;
    tb.Dock = DockStyle.Fill;
 
    Text = "Press any key";
    KeyPreview = true;
  }
 
  protected override void OnKeyDown(KeyEventArgs e)
  {
    AddLine(e.KeyData);
    base.OnKeyDown(e);
  }
 
  void AddLine(Keys keys)
  {
    tb.AppendText(keys.ToString() + Environment.NewLine);
  }
}