Cryptographic algorithms have been used not only to create robust ciphertexts but also to
generate cryptograms that, contrary to the classic goal of cryptography, are meant to be …

We construct a publicly verifiable protocol for proving computational work based on collision-
resistant hash functions and a new plausible complexity assumption regarding the existence …

In the standard definition of a commitment scheme, the sender commits to a message and
immediately sends the commitment to the recipient interested in it. However the sender may …

We develop new theoretical tools for proving lower-bounds on the (amortized) complexity of
certain functions in models of parallel computation. We apply the tools to construct a class of …

Availability is one of the three main components of computer security, along with
confidentiality and integrity. Denial of service (DoS) is a threat that potentially violates the …

Client puzzles are meant to act as a defense against denial of service (DoS) attacks by
requiring a client to solve some moderately hard problem before being granted access to a …

Various cryptographic puzzle schemes are proposed as a defense mechanism against
denial of service attack. But, all these puzzle schemes face a dilemma when there is a large …

Cloud-based services have become part of our day-to-day software solutions. The identity
authentication process is considered to be the main gateway to these services. As such …

By a computational puzzle we mean a mildly difficult computational problem that requires
resources (processor cycles, memory, or both) to solve. Puzzles have found a variety of uses …

Several cryptographic schemes and applications are based on functions that are both
reasonably efficient to compute and moderately hard to invert, including client puzzles for …