55 research outputs found
New Subclass Framework and Concrete Examples of Strongly Asymmetric Public Key Agreement
No full textStrongly asymmetric public key agreement (SAPKA) is a class of key exchange between Alice and Bob that was introduced in 2011. The greatest difference from the standard PKA algorithms is that Bob constructs multiple public keys and Alice uses one of these to calculate her public key and her secret shared key. Therefore, the number of public keys and calculation rules for each key differ for each user. Although algorithms with high security and computational efficiency exist in this class, the relation between the parameters of SAPKA and its security and computational efficiency has not yet been fully clarified. Therefore, our main objective in this study was to classify the SAPKA algorithms according to their properties. By attempting algorithm attacks, we found that certain parameters are more strongly related to the security. On this basis, we constructed concrete algorithms and a new subclass of SAPKA, in which the responsibility of maintaining security is significantly more associated with the secret parameters of Bob than those of Alice. Moreover, we demonstrate 1. insufficient but necessary conditions for this subclass, 2. inclusion relations between the subclasses of SAPKA, and 3. concrete examples of this sub-class with reports of implementational experiments
Implementation of a New Strongly-Asymmetric Algorithm and Its Optimization
No full textA new public key agreement (PKA) algorithm, called the strongly-asymmetric algorithm (SAA-5), was introduced by Accardi et al. The main differences from the usual PKA algorithms are that Bob has some independent public keys and Alice produces her public key by using some part of the public keys from Bob. Then, the preparation and calculation processes are essentially asymmetric. This algorithms has several free parameters more than the usual symmetric PKA algorithms and the velocity of calculation is largely dependent on the parameters chosen; however, the performance of it has not yet been tested. The purpose of our study was to discuss efficient parameters to share the key with high speeds in SAA-5 and to optimize SAA-5 in terms of calculation speed. To find efficient parameters of SAA-5, we compared the calculation speed with Diffie–Hellman (D-H) while varying values of some parameters under the circumstance where the length of the secret shared key (SSK) was fixed. For optimization, we discuss a more general framework of SAA-5 to find more efficient operations. By fixing the parameters of the framework properly, a new PKA algorithm with the same security level as SAA-5 was produced. The result shows that the calculation speed of the proposed PKA algorithm is faster than D-H, especially for large key lengths. The calculation speed of the proposed PKA algorithm increases linearly as the SSK length increases, whereas D-H increases exponentially
Metaplacenticeras subtilstriatum (Jimbo, 1894) (Cephalopoda: Ammonoidea) from the St Lucia Formation (Cretaceous), Zululand
No full textAn ammonite identified as Metaplacenticeras subtilstriatum (Jimbo, 1894) was recovered from a borehole in Zululand. It represents the first record of this genus and species outside the Pacific Realm, and permits a precise Late Campanian (Cretaceous) date for that section of the core. -Author
A New Class of Strongly Asymmetric PKA Algorithms: SAA-5
No full textA new class of public key agreement (PKA) algorithms called strongly-asymmetric algorithms (SAA) was introduced in a previous paper by some of the present authors. This class can be shown to include some of the best-known PKA algorithms, for example the Diffie–Hellman and several of its variants. In this paper, we construct a new version of the previous construction, called SAA-5, improving it in several points, as explained in the Introduction. In particular, the construction complexity is reduced, and at the same time, robustness is increased. Intuitively, the main difference between SAA-5 and the usual PKA consists of the fact that in the former class, B (Bob) has more than one public key and A (Alice) uses some of them to produce her public key and others to produce the secret shared key (SSK). This introduces an asymmetry between the sender of the message (B) and the receiver (A) and motivates the name for this class of algorithms. After describing the main steps of SAA-5, we discuss its breaking complexity assuming zero complexity of discrete logarithms and the computational complexity for both A and B to create SSK
Cryptanalysis on Asymmetric Structured Key Agreement Schemes
No full textWe study several asymmetric structured key agreement schemes based on
noncommutative matrix operations, including the recent proposal of Lizama as well as the strongly asymmetric algorithms SAA-3 and SAA-5 of Accardi
et al.\ We place them in a common algebraic framework for
public key agreement and identify simple structural conditions under which an
eavesdropper can reconstruct an effective key-derivation map and reduce key
recovery to solving linear systems over finite fields. We then show that the
three matrix-based schemes mentioned above all instantiate our algebraic framework and can therefore be broken in polynomial time from public
information alone. In particular, their security reduce to the hardness of
linear-algebraic problems and does not exceed that of the underlying discrete
logarithm problem. Our results demonstrate that the weakness of these schemes
is structural rather than parametric, and that minor algebraic modifications are insufficient to repair them
An Asymmetric Diffie-Hellman Protocol with Enhanced Efficiency through Parallelization
No full textTo ensure secure communication between two parties (Alice and Bob), Public Key Agreement (PKA) algorithms play a crucial role. The Diffie-Hellman (D-H) algorithm, introduced by W. Diffie and M. Hellman in 1976, is the most well-known PKA algorithm, based on exponentiation over a finite field. Over time, various PKA algorithms have been developed based on this original idea—these are referred to as D-H realizations or D-H algorithms. A common issue with D-H realizations is their computational inefficiency, particularly in environments with resource-constrained devices. This inefficiency arises from the high computational complexity of generating public and secret shared keys (SSKs), often resulting in communication delays.In this paper, we propose a modified D-H protocol designed to reduce the computational time required by one party, thereby decreasing the total time needed to establish the SSK in asymmetric environments where Alice and Bob have different computational capabilities. The core of this approach leverages the group homomorphism property of the underlying function to enable parallelization and reduce the complexity of Alice’s computations, together with an asymmetric key agreement structure in which both parties may follow distinct computational rules for public key and SSK generation.We demonstrate that the proposed protocol retains the security properties of the original D-H realizations, preserving the hardness of the discrete logarithm (DL), computational Diffie-Hellman (CDH), and decisional Diffie-Hellman (DDH) problems under an asymmetric setting. We also discuss its applicability to other cryptographic protocols. Experimental results show that the modified protocol significantly improves computational efficiency, particularly by reducing Alice\u27s computational burden through parallel processing. </p
The Effect of Cell Size on Tensile Strength and Stiffness of Cell Structure Fabricated by AM
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