Note on Constructing Constrained PRFs from OWFs with Constant Collusion Resistance

Constrained pseudorandom functions (CPRFs) are a type of PRFs that allows one to derive a constrained key $\mathsf{K}_C$ from the master key $\mathsf{K}$. While the master key $\mathsf{K}$ allows one to evaluate on any input as a standard PRF, the constrained key $\mathsf{K}_C$ only allows one to evaluate on inputs $x$ such that $C(x) = 1$. Since the introduction of CPRFs by Boneh and Waters (ASIACRYPT\u2713), Kiayias et al. (CCS\u2713), and Boyle et al. (PKC\u2714), there have been various constructions of CPRFs. However, thus far, almost all constructions (from standard assumptions and non-trivial constraints) are only proven to be secure if at most one constrained key $\mathsf{K}_C$ is known to the adversary, excluding the very recent work of Davidson and Nishimaki (EPRINT\u2718). Considering the interesting applications of CPRFs such as ID-based non-interactive key exchange, we desire CPRFs that are collusion resistance with respect to the constrained keys. In this work, we make progress in this direction and construct a CPRF for the bit-fixing predicates that are collusion resistance for a constant number of constrained keys. Surprisingly, compared to the heavy machinery that was used by previous CPRF constructions, our construction only relies on the existence of one-way functions

Effect of Cisternal Administration of Nicardipine Hydrochloride on Cerebral Vasospasm: A Preliminary Report

In six subarachnoid hemorrhage (SAH) cases due to aneurysmal rupture, effects of cisternal administration of Nicardipine hydrochloride (nicardipine) on vasospasm wer studied. Nicardipine is one of calcium antagonists. All aneurysms were clipped within 48 hr after the onset of SAH with ventricular and cisternal drainages. Subarachnoid clot was removed as much as possible. Nicardipine or mixture of nicardipine and urokinase was administered through cisternal drainage once a day for 10 days postoperatively. The dose of nicardipine was 2 mg or 4 mg, and that of urokinase was 6,000 units or 24,000 units. On the 7th day after the onset of SAH, angiograms were performed before and 30 min after the cisternal administration of nicardipine. Then the diameters of each arteries were compared in order to estimate the vasodilative effects of nicardipine angiographically. In this study nicardipine was considered to have some prophylactic effect on vasospasm because vasospasm was not observed either angiographically or clinically in 2 out of 3 severe SAH cases on CT