Lyra: Password-Based Key Derivation with Tunable Memory and Processing Costs.
Leonardo C. Almeida, Ewerton R. Andrade, Paulo S. L. M. Barreto, Marcos Antonio Simplicio Junior · 2014
Abstract. We present Lyra, a password-based key derivation scheme based on cryptographic sponges. Lyra was designed to be strictly sequen-tial (i.e., not easily parallelizable), providing strong security even against attackers that use multiple processing cores (e.g., custom hardware or a powerful GPU). At the same time, it is very simple to implement in soft-ware and allows legitimate users to fine-tune its memory and processing costs according to the desired level of security against brute force pass-word guessing. We compare Lyra with similar-purpose state-of-the-art solutions, showing how our proposal provides a higher security level and overcomes limitations of existing schemes. Specifically, we show that if we fix Lyra’s total processing time t in a legitimate platform, the cost of a memory-free attack against the algorithm is exponential, while the best-known result in the literature (namely, against the scrypt algorithm) is quadratic. In addition, for an identical same processing time, Lyra allows for a higher memory usage than its counterparts, further increasing the cost of brute force attacks.