Get iPhone UDID with mobileconfig file and verify response signature with PHP

I'm writing an application that needs users device UDID to be sent to server. I'm doing this installing simple udid.mobileconfig file on device. The udid.mobileconfig file is something like this:

<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">

<plist version="1.0">

<dict>

<key>PayloadContent</key>

<dict>

<key>URL</key>

<string>https://dl.iapp.ml/UDID/udidreceiver.php</string>

<key>DeviceAttributes</key>

<array>

<string>UDID</string>

</array>

</dict>

<key>PayloadOrganization</key>

<string>iApp.ml</string>

<key>PayloadDisplayName</key>

<string>UDID</string>

<key>PayloadVersion</key>

<integer>1</integer>

<key>PayloadUUID</key>

<string>92092767-E9CF-452A-A78C-FC3A9AE24308</string>

<key>PayloadIdentifier</key>

<string>ml.iApp.profile-service</string>

<key>PayloadDescription</key>

<string>In order to access your UDID please install this profile.</string>

<key>PayloadType</key>

<string>Profile Service</string>

</dict>

</plist>

This will successfully works and send device UDID to my PHP file in this case it's udidreceiver.php. But there's one problem. You can change device UDID that is sent to server with a local proxy server. iPhone will sign the response and then send it through network. So I want to check that sign in udidreceiver.php and if the UDID didn't changed accept it. Otherwise showing an error.

Update: The response from iPhone SMIME Type is application/pkcs7-signature But I can't do any simple operations with openssl pkcs7 command on it. Maybe it's not really a PKCS#7 file! What is the type? I uploaded iOS response to my server. Please have a look: http://rkstore.ir/1.p7s