Modifying Packet Header

Hi,

I am working on a project for a professor to collect smb packet headers on university network. Due to security reasons uid, mid, file path, etc. needs to be one-way encrypted.

I was wondering if anyone can help me figure out how i can modify these header fields in the dissected tree directly that is returned by libwireshark (edt->tree) before i can save this header to a pcap or a simple xml file with header in hex format.

Thank You