Hey Friends,
i am trying to verify the signature of our partner using x509 certificate
public.
i am able to retrieve the certificate from store but when i call the
CheckSignature method on the signedxml object then i get the following
unhandled exception.
"pCertContext is an invalid handle."

The Code that creates the exception is this
where SignedXML is a signedxml object.FoundCert is the public Certificate i
am retrieving from my store.
if (SignedXML.CheckSignature(FoundCert, false))

{

// Signature verified.

return true;

}

The Following is the Full  Code i am using:

//Get CertificateMethod

public X509Certificate2 GetX509Certificate(string IssuerName, string
SerialNumber,int i)

{

X509Certificate2 FoundCert = null;

X509Store store = null;

if (i==0)

{

store = new X509Store(StoreName.My, StoreLocation.LocalMachine);

}

else

{

store = new X509Store(StoreName.TrustedPeople, StoreLocation.LocalMachine);

}

store.Open(OpenFlags.ReadOnly);

X509CertificateCollection certs = store.Certificates;

// Search the certificates to find matching issuer name and serial number

foreach (X509Certificate2 cert in certs)

{

string aszcertserial=GetSerialNumber(cert.GetSerialNumber());

if ((IssuerName == cert.Issuer)

&& (SerialNumber == GetSerialNumber(cert.GetSerialNumber())))

{

// Find the match. Exit the loop.

FoundCert = cert;

break;

}

}

store.Close();

return FoundCert;

}

//VerifySignature method

public bool VerifySignature( )

{

XmlDocument aobDocument = new XmlDocument();

aobDocument.Load(System.Web.HttpContext.Current.Server.MapPath("ReadSample/R1_Signed_Sample.xml"));

XmlNodeList nodeList = aobDocument.GetElementsByTagName("X509IssuerName",
"http://www.w3.org/2000/09/xmldsig#");

XmlElement issuerNameElement = ((XmlElement)(nodeList[0]));

string issuerName = issuerNameElement.InnerText;

nodeList = aobDocument.GetElementsByTagName("X509SerialNumber",
"http://www.w3.org/2000/09/xmldsig#");

XmlElement serialNumberElement = (XmlElement)(nodeList[0]);

String serialNumber = serialNumberElement.InnerText;

// Dim MSCert As Microsoft.Web.Services.Security.X509.X509Certificate

X509Certificate2 FoundCert = GetX509Certificate(issuerName, serialNumber,1);

return VerifySignature(FoundCert);

}

public bool VerifySignature(X509Certificate2 FoundCert)

{

Microsoft.Web.Services3.SoapEnvelope aobDocument = new
Microsoft.Web.Services3.SoapEnvelope();

//XmlDocument aobDocument = new XmlDocument();

aobDocument.PreserveWhitespace = true;

aobDocument.Load(System.Web.HttpContext.Current.Server.MapPath("ReadSample/R1_Signed_Sample.xml"));

SignedXML SignedXML = new SignedXML((XmlDocument)(aobDocument));

XmlNodeList nodeList = aobDocument.GetElementsByTagName("Signature",
"http://www.w3.org/2000/09/xmldsig#");

SignedXML.LoadXml((XmlElement)(nodeList[0]));

try

{

if (SignedXML.CheckSignature(FoundCert, false))

{

// Signature verified.

return true;

}

else

{

//Signature verification failed.

return false;

}

}

catch (Exception ex)

{

throw;

}

}

private string GetSerialNumber(byte[] SerialNumber)

{

long[] outputDigits=new long[39];

int currentByte;

for (currentByte = SerialNumber.GetUpperBound(0); (currentByte >= 1);
currentByte = (currentByte-1))

{

outputDigits[38] = (outputDigits[38] +
(Convert.ToInt64(SerialNumber[currentByte])));

flattenDigits(ref outputDigits, 256);

}

outputDigits[38] = (outputDigits[38] + ((long)(SerialNumber[0])));

flattenDigits(ref outputDigits);

return digitsToString(outputDigits);

}

private void flattenDigits(ref long[] bumpyDigits)

{

flattenDigits(ref bumpyDigits, 1);

}

private void flattenDigits(ref long[] bumpyDigits, int multiplier)

{

long nextValueAddition = 0;

for (int currentDigit = bumpyDigits.GetUpperBound(0); (currentDigit >= 0);
currentDigit = (currentDigit-1))

{

bumpyDigits[currentDigit] =
bumpyDigits[currentDigit]*Convert.ToInt64(multiplier);

bumpyDigits[currentDigit] = (bumpyDigits[currentDigit] + nextValueAddition);

nextValueAddition = bumpyDigits[currentDigit]/10;

bumpyDigits[currentDigit] = (bumpyDigits[currentDigit] % 10);

}

}

private string digitsToString(long[] digits)

{

int currentDigit = 0;

StringBuilder outputString = new StringBuilder();

while (((digits[currentDigit] == 0)

&& currentDigit != 38))

{

currentDigit++;

}

do

{

outputString.Append(digits[currentDigit].ToString());

currentDigit++;

}

while (currentDigit < 39);

return outputString.ToString();

}

The Following is the Xml

 <?xml version="1.0" encoding="UTF-8" ?>
- <B:Envelope xmlns:B="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:A="http://www.routeone.com/namespace.messaging.diag#"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
- <SOAP:Header
xmlns:SOAP-SEC="http://schemas.xmlsoap.org/soap/security/2000-12"
xmlns:SOAP="http://schemas.xmlsoap.org/soap/envelope/">
- <SOAP-SEC:Signature SOAP:mustUnderstand="1">
- <Signature xmlns="http://www.w3.org/2000/09/xmldsig#"
xmlns:C="http://www.routeone.com/namespace.messaging.CreditApplication#"
xmlns:wsse="http://schemas.xmlsoap.org/ws/2002/07/secext">
- <SignedInfo>
 <CanonicalizationMethod
Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
 <SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1" />
- <Reference URI="#Body">
- <Transforms>
 <Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#" />
 </Transforms>
 <DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1" />
 <DigestValue>niQfM6RR1CP+V1Puf9FlaXRNcFQ=</DigestValue>
 </Reference>
 </SignedInfo>
 <SignatureValue>Ii68Od4N0zOe+UwJyBDe1aQlC1YbteOk4YNjyOal9m6f7KbO4SqPdaX4CJZIIt1Z5f7iOgzhK6nuCi08RPyqXPvdeuivNNOq6/4a7iJZxQD2PMAFBVAVwAuLmIRAh0u6MkzA/u0069JvP90mOpYtG1euXf5oSKI+XCmdSKIBjv5FNmg9XTaruy2cg3Iz+KOUInMPnG7AJcmJRnaLLr/5za6Bu1CgpeS0/aBVhf2xpF7/A9qa/sjiQR2dfwPM+InawXV94SD8HEd6QFzfE5WxrWLkVXOBeiCyNvYXX9CTcmPQFUnvVxA1+L9TMx4reb835ZT0Hi2aP2hu7PQiWAaFdw==</SignatureValue>
- <KeyInfo>
- <X509Data>
 <X509Certificate />
- <X509IssuerSerial>
 <X509IssuerName>OU=www.verisign.com/CPS Incorp.by Ref. LIABILITY LTD.(c)97
VeriSign, OU=VeriSign International Server CA - Class 3, OU="VeriSign,
Inc.", O=VeriSign Trust Network</X509IssuerName>
 <X509SerialNumber>160283950701092051351433675048676869301</X509SerialNumber>
 </X509IssuerSerial>
 </X509Data>
 </KeyInfo>
 </Signature>
 </SOAP-SEC:Signature>
 </SOAP:Header>
- <B:Body id="Body"
xmlns:SOAP-SEC="http://schemas.xmlsoap.org/soap/security/2000-12"
xmlns:SOAP="http://schemas.xmlsoap.org/soap/envelope/">
- <A:Diagnostic>
- <A:DiagnosticMessage>
 <A:RequestMessage>100027</A:RequestMessage>
 </A:DiagnosticMessage>
 <A:SourceIdentifier>RouteOne</A:SourceIdentifier>
 </A:Diagnostic>
 </B:Body>
 </B:Envelope>

The Full Description of the Error is

System.Security.Cryptography.CryptographicException was unhandled by user
code
 Message="pCertContext is an invalid handle."
 Source="System"
 StackTrace:
      at
System.Security.Cryptography.CAPI.CertAddCertificateLinkToStore(SafeCertStoreHandle
hCertStore, SafeCertContextHandle pCertContext, UInt32 dwAddDisposition,
SafeCertContextHandle ppStoreContext)
      at
System.Security.Cryptography.X509Certificates.X509Utils.ExportToMemoryStore(X509Certificate2Collection
collection)
      at
System.Security.Cryptography.X509Certificates.X509Chain.BuildChain(IntPtr
hChainEngine, SafeCertContextHandle pCertContext, X509Certificate2Collection
extraStore, OidCollection applicationPolicy, OidCollection
certificatePolicy, X509RevocationMode revocationMode, X509RevocationFlag
revocationFlag, DateTime verificationTime, TimeSpan timeout,
SafeCertChainHandle& ppChainContext)
      at
System.Security.Cryptography.X509Certificates.X509Chain.Build(X509Certificate2
certificate)
      at
System.Security.Cryptography.Xml.SignedXml.CheckSignature(X509Certificate2
certificate, Boolean verifySignatureOnly)
      at Signer.VerifySignature(X509Certificate2 FoundCert) in
c:\Inetpub\wwwroot\TestMSMQ\MessageSigning.aspx.cs:line 201
      at Signer.VerifySignature() in
c:\Inetpub\wwwroot\TestMSMQ\MessageSigning.aspx.cs:line 152
      at MessageSigning.Page_Load(Object sender, EventArgs e) in
c:\Inetpub\wwwroot\TestMSMQ\MessageSigning.aspx.cs:line 65
      at System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp,
Object o, Object t, EventArgs e)
      at System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object
sender, EventArgs e)
      at System.Web.UI.Control.OnLoad(EventArgs e)
      at System.Web.UI.Control.LoadRecursive()
      at System.Web.UI.Page.ProcessRequestMain(Boolean
includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)