[Serusers] Compare "Contact" and "Digest username" in REGISTER

Hi list, we operate a commercial PSTN-replacement service. For my setup we need to restrict the contact-information that the user register with. Only the assigned E.164 number in "Contact" shall be allowed with a specific "Digest username" in REGISTER Our contact and digest_username are very similar and only differ by a prefixed '0' in contact. E.g. Contact: <sip:0123456@cpe.network:5060;transport=UDP> Authorization: Digest username="123456", realm="network...... Is it possible to compare these two and only allow registration if the comparison returns true? Thanks for your help and best regards, Gerhard __________________________________________________________________________________ Dieses Mail wurde vom Infotech SecureMail Service ueberprueft und fuer sicher befunden. Fuer weitere Informationen zu Infotech SecureMail Service waehlen Sie bitte: www.infotech.at/securemail/ This email has been scanned by Infotech SecureMail Service and it has been classified as secure. For more information on Infotech SecureMail direct your web browser to: www.infotech.at/securemail/