More Efficient Server Assisted One Time Signatures

Server assisted one time signature scheme was recently presented as a nonrepudiation service for mobile and constrained devices. However, the scheme suffered with high storage requirements for the virtual server and high memory requirements for the mobile client. We improve the scheme by significantly reducing virtual server storage requirements as well as mobile client memory requirements. More precisely, the virtual server storage requirements in our scheme are reduced by a factor of more than 80 compared to the original scheme. Further, memory requirements for the mobile client are reduced by a factor of more than 130. This is done by generating various quantities pseudorandomly and storing just their cryptographic hash (instead of storing them fully) wherever possible, while still being able to perform dispute resolution.