Missing crypto [null] for signature entry

Hello,

I am new to the SOAPUI. I have SOAP UI 4.0.1. I am using it for testing some webservices exposed from one of our vendors (SaaS).
They require us to send the HMAC SHA1 signature in the header. I have the private key and I generated the HMAC SHA1 signature. I am wondering if somebody can help me with the steps to attach the signature in the header of the request. Following is a sample header and body of the request I am sending. I manually added the parameters in the request.


<soapenv:Envelope xmlns:cat="http://www.XXX.com/Webservices/Catalog" xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
<soapenv:Header><wsse:Security xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd"/>

<cat:AuthHeader>
<!--Optional:-->
<cat:CorpName>XYZ</cat:CorpName>
<!--Optional:-->
<cat:UserId>soapadmin</cat:UserId>
<!--Optional:-->
<cat:Signature>ad123e8e40a958e8da0337146355661ad81b377g</cat:Signature>
</cat:AuthHeader>
</soapenv:Header>
<soapenv:Body>
<cat:Search>
<!--Optional:-->
<cat:query>
<!--Optional:-->
<cat:ObjectId></cat:ObjectId>
<!--Optional:-->
<cat:Title></cat:Title>
<!--Optional:-->
<cat:Provider>Parkway</cat:Provider>
<cat:PageNum>0</cat:PageNum>
<!--Optional:-->
<cat:Subject></cat:Subject>
<!--Optional:-->
<cat:Competencies></cat:Competencies>
<!--Optional:-->
<cat:Descr></cat:Descr>
<cat:Type>ONLINE</cat:Type>
<cat:LocatorNumber>0</cat:LocatorNumber>
<!--Optional:-->
<cat:Locations></cat:Locations>
<!--Optional:-->
<cat:Instructor></cat:Instructor>
</cat:query>
</cat:Search>
</soapenv:Body>
</soapenv:Envelope>

Here is the response I am getting
<ExceptionInfo>Exception Message: Invalid Signature;Exception Target Method: Search</ExceptionInfo>

error Log -
ERROR:java.lang.Exception: Missing crypto [null] for signature entry

Thanks in advance.