Dynamic key cryptography validates mobile device users to cloud services by uniquely identifying the user's electronic device using a very wide range of hardware, firmware, and software minutiae, user secrets, and user biometric values found in or collected by the device. Processes for uniquely identifying and validating the device include: selecting a subset of minutia from a plurality of minutia types; computing a challenge from which the user device can form a response based on the selected combination of minutia; computing a set of pre-processed responses that covers a range of all actual responses possible to be received from the device if the combination of the particular device with the device's collected actual values of minutia is valid; receiving an actual response to the challenge from the device; determining whether the actual response matches any of the pre-processed responses; and providing validation, enabling authentication, data protection, and digital signatures.