  Criminals are increasingly using mobile based communication applications,
like WhatsApp, that have end-to-end encryption to connect to each other. This
makes traditional analysis of call graphs, or traffic analysis, virtually
impossible and so is a hindrance for law enforcement personnel. Old methods of
traffic analysis have been rendered useless and criminals, including arms
dealers and terrorists, are able to engage in criminal activity undetected by
police. At present, law enforcement must use extensive manual effort to parse
data provided by cell companies to extract information. We have built a system
that analyses cellular GPRS metadata and builds a profile and finds potential
call connections explicitly which are implicit in the dataset. This paper
describes our approach and system in detail and includes results of our
evaluation using an anonymized dataset from Delhi Police. Our system permits
call graph analysis to be done, and significantly reduces the time needed from
the data analysis process.
