In this paper, we define and explore proofs of retrievability (PORs). A POR scheme enables an archive or back-up service (prover) to produce a concise proof that a user (verifier) can retrieve a target file F, that is, that the archive retains and reliably transmits file data sufficient for the user to recover F in its entirety.

The MQV key agreement protocol, a technique included in recent standards, is shown in its basic form to be vulnerable to an unknown key-share attack. Although the attack's practical impact on security is minimal---a key confirmation step easily prevents it---the attack is noteworthy in the principles it illustrates about protocol design. First, minor “efficiency improvements” can significantly alter the security properties of a protocol. Second, protocol analysis must consider potential interactions with all parties, not just those that are normally online. Finally, attacks must be assessed in terms of system requirements, not just in isolation.

The Montgomery inverse of b module a is b/sup -1/2/sup n/ mod a, where n is the number of bits in a. The right-shifting binary algorithm for modular inversion is shown naturally to compute the new inverse in fewer operations than the ordinary modular inverse. The new inverse facilitates recent work by Koc on modular exponentiation and has other applications in cryptography.>

Signal processors and array processors use buffers to hold signal samples and access the buffer elements in specified orders to effect various processing algorithms. Array processor libraries normally only provide language level support for one-dimensional buffers and for address sequences that are, themselves, essentially one-dimensional. The SPS-1000, developed by Signal Processing Systems, Inc., (SPS), uses high speed address generation hardware and a sophisticated set of FORTRAN routines, to significantly expand upon these capabilities. The library routines allow the definitions of multi-dimensional buffers, and, with the use of nested loop constructions (similar to the "implied DO" facility of FORTRAN READ or WRITE statements) the user may specify continuously evolving address sequences which can effect a continuous flow of n-dimensional data objects (n > = 0) through these buffers in an efficient manner. Examples illustrating both the power and the simplicity of these specifications are given.