ProMACs: Progressive and Resynchronizing MACs for Continuous Efficient Authentication of Message Streams

Efficiently integrity verification of received data requires Message Authentication Code (MAC) tags. However, while security calls for rather long tags, in many scenarios this contradicts other requirements. Examples are strict delay requirements (e.g., robot or drone control) or resource-scarce settings (e.g., LoRaWAN networks with limited battery capacity). Prior techniques suggested truncation of MAC tags, thus trading off linear performance gain for exponential security loss. To achieve security of full-length MACs with short(er) tags, we introduce Progressive MACs (ProMACs) -- a scheme that uses internal state to gradually increase security upon reception of subsequent messages. We provide a formal framework and propose a provably secure, generic construction called Whips. We evaluate applicability of ProMACs in several realistic scenarios and demonstrate example settings where ProMACs can be used as a drop-in replacement for traditional MACs.