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Recently a lot of attention is paid to the search for efficiently implementable MDS matrices for lightweight symmetric primitives. Most previous work concentrated on locally optimizing the multiplication with single matrix elements. Separate from this line of work, several heuristics were developed to find shortest linear straightline programs. Solving this problem actually corresponds to globally optimizing multiplications by matrices. In this work we combine those, so far largely independent lines of work. As a result, we achieve implementations of known, locally optimized, and new MDS matrices that significantly outperform all implementations from the literature. Interestingly, almost all previous locally optimized constructions behave very similar with respect to the globally optimized implementation. As a side effect, our work reveals the so far best implementation of the Aes Mix- Columns operation with respect to the number of XOR operations needed.

Passwords are still by far the most widely used form of user authentication, for applications ranging from online banking or corporate network access to storage encryption. Password guessing thus poses a serious threat for a multitude of applications. Modern password hashes are specically designed to slow down guessing attacks. However, having exact measures for the rate of password guessing against determined attackers is non-trivial but important for evaluating the security for many systems. Moreover, such information may be valuable for designing new password hashes, such as in the ongoing password hashing competition (PHC).In this work, we investigate two popular password hashes, bcrypt and scrypt, with respect to implementations on non-standard computing platforms. Both functions were specically designed to only allow slow-rate password derivation and, thus, guessing rates. We develop a methodology for fairly comparing dierent implementations of password hashes, and apply this methodology to our own implementation of scrypt on GPUs, as well as existing implementations of bcrypt and scrypt on GPUs and FPGAs.

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In this work we describe the implementation details of a protocol suite for a secure and reliable over-the-air reprogramming of wireless restricted devices. Although, recently forward error correction codes aiming at a robust transmission over a noisy wireless medium have extensively been discussed and evaluated, we believe that the clear value of the contribution at hand is to share our experience when it comes to a meaningful combination and implementation of various multihop (broadcast) transmission protocols and custom-fit security building blocks: For a robust and reliable data transmission we make use of fountain codes a.k.a. rateless erasure codes and show how to combine such schemes with an underlying medium access control protocol, namely a distributed low duty cycle medium access control (DLDC-MAC). To handle the well known problem of packet pollution of forward-error-correction approaches where an attacker bogusly modifies or infiltrates some minor number of encoded packets and thus pollutes the whole data stream at the receiver side, we apply homomorphic message authentication codes (HomMAC). We discuss implementation details and the pros and cons of the two currently available HomMAC candidates for our setting. Both require as the core cryptographic primitive a symmetric block cipher for which, as we will argue later, we have opted for the PRESENT, PRIDE and PRINCE (exchangeable) ciphers in our implementation.