E theory in seven dimensions

We construct the non-linear realisation of the semi-direct product of E11 and its vector representation in its decomposition into the subalgebra GL(7)x SL(5) to find a seven dimensional theory. The resulting equations of motion essentially follow from the Dynkin diagram of E11 and if one restricts them to contain only the usual fields of supergravity and the derivatives with respect to the usual coordinates of spacetime then these are the equations of motion of seven dimensional supergravity.Comment: 36 page

Efficient Threshold-Optimal ECDSA

This paper proposes a threshold-optimal ECDSA scheme based on the first threshold signature scheme by Gennaro et al. with efficient non-interactive signing for any $t+1$ signers in the group, provided the total group size is more than twice the threshold $t$. The scheme does not require any homomorphic encryption or zero-knowledge proofs and is proven to be robust and unforgeable with identifiable aborts tolerating at most $t$ corrupted participants. The security of the scheme is proven in a simulation-based definition, assuming DDH and that ECDSA is existentially unforgeable under chosen message attack. To evaluate the performance of the protocol, it has been implemented in C++ and the results demonstrate the non-interactive signing phase takes 0.12ms on average meaning over 8000 signatures can be created per second. With pre-signing phase, it takes 3.35ms in total, which is over 144 times faster than the current state of the art