From the Publisher:
A valuable reference for the novice as well as for the expert who needs a wider scope of coverage within the area of cryptography, this book provides easy and rapid access of information and includes more than 200 algorithms and protocols; more than 200 tables and figures; more than 1,000 numbered definitions, facts, examples, notes, and remarks; and over 1,250 significant references, including brief comments on each paper.

Handbook of Applied Cryptography

In several distributed systems a user should only be able to access data if a user posses a certain set of credentials or attributes. Currently, the only method for enforcing such policies is to employ a trusted server to store the data and mediate access control. However, if any server storing the data is compromised, then the confidentiality of the data will be compromised. In this paper we present a system for realizing complex access control on encrypted data that we call ciphertext-policy attribute-based encryption. By using our techniques encrypted data can be kept confidential even if the storage server is untrusted; moreover, our methods are secure against collusion attacks. Previous attribute-based encryption systems used attributes to describe the encrypted data and built policies into user's keys; while in our system attributes are used to describe a user's credentials, and a party encrypting data determines a policy for who can decrypt. Thus, our methods are conceptually closer to traditional access control methods such as role-based access control (RBAC). In addition, we provide an implementation of our system and give performance measurements.

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Ciphertext-Policy Attribute-Based Encryption

As more sensitive data is shared and stored by third-party sites on the Internet, there will be a need to encrypt data stored at these sites. One drawback of encrypting data, is that it can be selectively shared only at a coarse-grained level (i.e., giving another party your private key). We develop a new cryptosystem for fine-grained sharing of encrypted data that we call Key-Policy Attribute-Based Encryption (KP-ABE). In our cryptosystem, ciphertexts are labeled with sets of attributes and private keys are associated with access structures that control which ciphertexts a user is able to decrypt. We demonstrate the applicability of our construction to sharing of audit-log information and broadcast encryption. Our construction supports delegation of private keys which subsumesHierarchical Identity-Based Encryption (HIBE).

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Attribute-based encryption for fine-grained access control of encrypted data

Suppose we are given a proof of knowledge P in which a prover demonstrates that he knows a solution to a given problem instance. Suppose also that we have a secret sharing scheme S on n participants. Then under certain assumptions on P and S, we show how to transform P into a witness indistinguishable protocol, in which the prover demonstrates knowledge of the solution to some subset of n problem instances out of a collection of subsets denned by S. For example, using a threshold scheme, the prover can show that he knows at least d out of n solutions without revealing which d instances are involved. If the instances axe independently generated, we get a witness hiding protocol, even if P did not have this property. Our results can be used to efficiently implement general forms of group oriented identification and signatures. Our transformation produces a protocol with the same number of rounds as P and communication complexity n times that of P. Our results use no unproven complexity assumptions.

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Proofs of Partial Knowledge and Simplified Design of Witness Hiding Protocols

We construct an Attribute-Based Encryption (ABE) scheme that allows a user's private key to be expressed in terms of any access formula over attributes. Previous ABE schemes were limited to expressing only monotonic access structures. We provide a proof of security for our scheme based on the Decisional Bilinear Diffie-Hellman (BDH) assumption. Furthermore, the performance of our new scheme compares favorably with existing, less-expressive schemes.

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Attribute-based encryption with non-monotonic access structures

100 mg/day of clomiphene-citrate is administered for 5 days from the fifth day of the menstrual cycle. Ultrasonography and highly sensitive immunoassay of urinary estrogen (Mochida Co., Japan) are used to decide the beginning of urinary LH measurement every 4 hr. We do laparoscopic egg collection 2628 hr after the onset of LH surge or 36-37 hr after HCG injection, depending on the maximum follicular diameter and urinary LH level measured with Hi-Gonavis (Mochida Co.). Incubation is done with Wittingham's T 6 medium including 10% (IM) or 15% (GM) inactivated patient's serum under conditions of mixed gas (5% CO2, 5% 02, 90% N2). Six hours after preincubation of the ovum, 3-5 • 10~/ mt of washed sperm is added and incubated for 16 hr of fertilization time. Then the embryo is moved to growing medium and cultured for 36 hr. Fifty-six hours after egg recovery, the embryo is replaced into the uterus with Monash ET Catheter Type 2. Table I. Clinical Results of IVF and ET (February-September 1983, Tohoku University, Sendai)

In vitro fertilization and embryo transfer at Tohoku University, Sendai, Japan

Sumner [7] proved that every connected K 1,3-free graph of even order has a perfect matching. He also considered graphs of higher connectivity and proved that if m ≥ 2, every m-connected K 1,m+1-free graph of even order has a perfect matching. In [6], two of the present authors obtained a converse of sorts to Sumner’s result by asking what single graph one can forbid to force the existence of a perfect matching in an m-connected graph of even order and proved that a star is the only possibility. In [2], Fujita et al. extended this work by considering pairs of forbidden subgraphs which force the existence of a perfect matching in a connected graph of even order. But they did not settle the same problem for graphs of higher connectivity. In this paper, we give an answer to this problem. Together with the result in [2], a complete characterization of the pairs is given.

A pair of forbidden subgraphs and perfect matchings in graphs of high connectivity

A graph is called $2K_2$-free if it does not contain two independent edges as an induced subgraph. Mou and Pasechnik conjectured that every $\frac{3}{2}$-tough $2K_2$-free graph with at least three vertices has a spanning trail with maximum degree at most $4$. In this paper, we confirm this conjecture. We also provide examples for all $t < \frac{5}{4}$ of $t$-tough graphs that do not have a spanning trail with maximum degree at most $4$.

Spanning trails with maximum degree at most 4 in $2K_2$-free graphs

A graphG is said to bek-path-connected if every pair of distinct vertices inG are joined by a path of length at leastk. We prove that if max{degGx, degGy}≥k for every pair of verticesx,y withdG(x,y)=2 in a 2-connected graphG, wheredG(x,y) is the distance betweenx andy inG, thenG isk-path-connected.

Fan-type theorem for path-connectivity

The purpose of this investigation was to analyze how left ventricular assist device (LVAD) with a centrifugal pump alters left ventricular diastolic hemodynamics and energy by means of a left ventricular pressure volume relationship. Fifteen anesthetized normal pig hearts were studied after placement of an apical drainage LVAD with a centrifugal pump. Indices of the left ventricular isovolumic relaxation phase, left ventricular filling phase and general hemodynamic data were recorded with the LVAD in on and off situations. The pump assist rate was adjusted to 25%, 50% and 75%. Left ventricular stroke work, with a high correla- tion with oxygen consumption, decreased as the assist rate increased. Left ventricular relax- ation delayed as the assist rate increased, but the atrioventricular pressure gradient increased in the left ventricular rapid filling phase. This finding clarifies left ventricular rapid filling. In this study, it was suggested that although left ventricular isovolumic relaxation was af- fected, 75% assistance is the most effective for the pump flow in terms of circulation support and restoration of cardiac function. (Ann Thorac Cardiovasc Surg 2002; 8: 275-80)

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Akira Saito

Papers

In vitro fertilization and embryo transfer at Tohoku University, Sendai, Japan

A pair of forbidden subgraphs and perfect matchings in graphs of high connectivity

Spanning trails with maximum degree at most 4 in $2K_2$-free graphs

Fan-type theorem for path-connectivity

Effects of a left ventricular assist device with a centrifugal pump on left ventricular diastolic hemodynamics.