A system for authenticating mobile device users transparently is disclosed. This invention improves on the existing flaws by deriving encryption keys from environmental condition data when the user and device are trusted. The keys are then cryptographically hashed and compared with repository hashed data to determine if the conditions match a prior set of conditions. If a match is found and trust factors are sufficient, the system uses the condition data to decrypt a master key that allows access to secure data in the same manner as would a user-provided password. The security system cannot be bypassed if the device is stolen, as an attacker would have to replicate the exact environment and behavioral attributes employed and learned from the user without any knowledge as to the factors that constitute them because the factors are not maintained by the system.