The electromagnetic spectrum is a valued shared resource. Its scientific use allows us to learn about our universe, measure and monitor our planet, and communicate scientific data. The use of the spectrum is managed by national, regional, and global regulatory frameworks. There are increasing demands for new or extended allocations because of vast technological advances in the past few years. Understanding spectrum management is important in the successful planning and execution of missions and instruments, as well as in determining the potential source of radio frequency interference in existing data and instruments, and in working to ameliorate its impact. This paper provides a summary of this framework for radio scientists and engineers.

We show that interaction in any zero-knowledge proof can be replaced by sharing a common, short, random string. We use this result to construct the first public-key cryptosystem secure against chosen ciphertext attack.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 1988.

A new method for constructing wide-sense nonblocking networks is presented. Application of this method yields (among other things) wide-sense nonblocking generalized connectors with n inputs and outputs and size $O( n\log n )$, and with depth k and size $O ( n^{1 + 1/k} ( \log n )^{1 - 1/k} )$.

This paper presents an extremely efficient, non-interactive protocol for verifiable secret sharing. Verifiable secret sharing (VSS) is a way of bequeathing information to a set of processors such that a quorum of processors is needed to access the information. VSS is a fundamental tool of cryptography and distributed computing. Seemingly difficult problems such as secret bidding, fair voting, leader election, and flipping a fair coin have simple one-round reductions to VSS. There is a constant-round reduction from Byzantine Agreement to non-interactive VSS. Non-interactive VSS provides asynchronous networks with a constant-round simulation of simultaneous broadcast networks whenever even a bare majority of processors are good. VSS is constantly repeated in the simulation of fault-free protocols by faulty systems. As verifiable secret sharing is a bottleneck for so many results, it is essential to find efficient solutions.

Two variants of the concept "non-blocking" have been defined in the literature: "strictly" non-blocking and "wide-sense" non-blocking. Hitherto, only toy examples were known of connectors that are wide-sense non-blocking but not strictly non-blocking, and these examples are more expensive than comparable strictly non-blocking connectors. In this paper we show for the first time how wide-sense non-blocking connectors can be less expensive than comparable strictly non- blocking connectors. In the simplest case we show that strictly non-blocking n-connectors with depth 2 must have ~2(n 2) edges, but wide-sense non-blocking n-connectors with depth 2 can have O(n 3/2 (log n) I/2) edges.

We present a novel cryptographic algorithm for Byzantine agreement in a network with l=O(n) faulty processors and in the most adversarial setting. Our algorithm requires, once and for all, O(t) rounds of preprocessing. Afterwards it allows us to reach each individual Byzantine agreement in constant expected time. Our solution does not make use of any trusted party.

We prove the conjectured 2T-1 pound on the diameter of a surviving quote graph from which T edges are removed, under the assumption that a minimal path routing is used we also prove the related conjecture for node failure, and combine the results into a more general theorem.