19 research outputs found
A randomized analog of Chaum β van Antwerpen undeniable signature
ΠΡΠ΅Π΄Π»Π°Π³Π°Π΅ΡΡΡ ΠΌΠΎΠ΄ΠΈΡΠΈΠΊΠ°ΡΠΈΡ Π½Π΅ΠΎΡΠΏΠΎΡΠΈΠΌΠΎΠΉ ΠΏΠΎΠ΄ΠΏΠΈΡΠΈ Π. Π§Π°ΡΠΌΠ° ΠΈ Π₯. Π²Π°Π½ ΠΠ½ΡΠ²Π΅ΡΠΏΠ΅Π½Π°, ΠΎΡΠ½ΠΎΠ²Π°Π½Π½Π°Ρ Π½Π° Π³ΡΡΠΏΠΏΠ΅ ΡΠΎΡΠ΅ΠΊ ΡΠ»Π»ΠΈΠΏΡΠΈΡΠ΅ΡΠΊΠΎΠΉ ΠΊΡΠΈΠ²ΠΎΠΉ. ΠΠ»Π³ΠΎΡΠΈΡΠΌ ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΏΠΎΠ΄ΠΏΠΈΡΠΈ Π΄ΠΎΠΏΠΎΠ»Π½Π΅Π½ ΠΏΡΠ΅Π΄Π²Π°ΡΠΈΡΠ΅Π»ΡΠ½ΡΠΌ ΡΡΠ°ΠΏΠΎΠΌ ΡΠ°Π½Π΄ΠΎΠΌΠΈΠ·Π°ΡΠΈΠΈ. ΠΠ»Ρ ΠΏΡΠΎΡΠΎΠΊΠΎΠ»ΠΎΠ² ΠΏΡΠΎΠ²Π΅ΡΠΊΠΈ ΠΏΠΎΠ΄ΠΏΠΈΡΠΈ ΠΈ ΠΎΡΠΊΠ°Π·Π° ΠΎΡ Π½Π΅Ρ ΠΏΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½ΠΎ Π΄Π²Π° Π²Π°ΡΠΈΠ°Π½ΡΠ° Π²ΡΠΏΠΎΠ»Π½Π΅Π½ΠΈΡ. ΠΠΎΠΊΠ°Π·Π°Π½Ρ ΡΠ΅ΠΎΡΠ΅ΠΌΡ, ΠΏΠΎΠΊΠ°Π·ΡΠ²Π°ΡΡΠΈΠ΅, ΡΡΠΎ ΡΡΠΈ ΠΏΡΠΎΡΠΎΠΊΠΎΠ»Ρ ΠΎΡΠ²Π΅ΡΠ°ΡΡ ΡΠ²ΠΎΠ΅ΠΌΡ Π½Π°Π·Π½Π°ΡΠ΅Π½ΠΈΡ. ΠΠΏΠΈΡΠ°Π½ ΡΠΏΠΎΡΠΎΠ± ΠΏΡΠ΅ΠΎΠ±ΡΠ°Π·ΠΎΠ²Π°Π½ΠΈΡ Π½Π΅ΠΎΡΠΏΠΎΡΠΈΠΌΠΎΠΉ ΠΏΠΎΠ΄ΠΏΠΈΡΠΈ Π² ΠΎΠ±ΡΡΠ½ΡΡ ΡΠΈΡΡΠΎΠ²ΡΡ ΠΏΠΎΠ΄ΠΏΠΈΡΡ, ΠΏΡΠΎΠΈΠ»Π»ΡΡΡΡΠΈΡΠΎΠ²Π°Π½Π½ΡΠΉ Π½Π° ΠΏΡΠΈΠΌΠ΅ΡΠ΅ ΡΡ
Π΅ΠΌΡ ΡΠΈΡΡΠΎΠ²ΠΎΠΉ ΠΏΠΎΠ΄ΠΏΠΈΡΠΈ Π¨Π½ΠΎΡΡΠ°
Chameleon Signature from Bilinear Pairing
Chameleon signatures are non-interactive signatures based on a hash-and-sign paradigm, and similar in efficiency to regular signatures. The distinguishing characteristic of chameleon signatures is that there are non-transferable, with only the designated recipient capable of asserting its validity. In this paper, we introduce a new ID-based chameleon hash function based on bilinear pairing and build the ID-based chameleon signature scheme. Compared with the conventional chameleon hashing functions, the owner of a public hash key in the ID-based chameleon hashing scheme does not necessarily need to retrieve the associated secret key. The scheme enjoys all the attributes in the normal chameleon signature and the added characteristics of ID-based cryptography based on bilinear pairing
Hardware Implementations of a Variant of the ZΓ©mor-Tillich Hash Function: Can a Provably Secure Hash Function be very efficient ?
Hash functions are widely used in Cryptography, and hardware implementations of hash functions are of interest in a variety of contexts such as speeding up the computations of a network server or providing authentication in small electronic devices such as RFID tags. Provably secure hash functions, the security of which relies
on the hardness of a mathematical problem, are particularly appealing for security, but they used to be too inefficient in practice. In this paper, we study the efficiency
in hardware of ZT\u27, a provably secure hash function based on the ZΓ©mor-Tillich hash function. We consider three kinds of implementations targeting a high throughput and a low area in different ways. We first present a high-speed implementation of ZT\u27 on
FPGA that is nearly half as efficient as state-of-the-art SHA implementations in terms of throughput per area. We then focus on area reduction and present an ASIC implementation of ZT\u27 with much smaller area costs than SHA-1 and even than SQUASH, which was specially designed for low-cost RFID tags. Between these two extreme implementations, we show that the throughput and area can be traded with a lot of flexibility. Finally, we show that the inherent parallelism of ZT\u27 makes it particularly suitable for applications requiring high speed hashing of very long messages. Our work,
together with existing reasonably efficient software implementations, shows that this variant of the ZΓ©mor-Tillich hash function is in fact very practical for a wide range of applications, while having a security related to the hardness of a mathematical problem
and significant additional advantages such as scalability and parallelism
Key-Exposure Free Chameleon Hashing and Signatures Based on Discrete Logarithm Systems
Chameleon signatures simultaneously provide the properties of
non-repudiation and non-transferability for the signed message.
However, the initial constructions of chameleon signatures suffer
from the problem of key exposure. This creates a strong
disincentive for the recipient to forge signatures, partially
undermining the concept of non-transferability. Recently, some
specific constructions of discrete logarithm based chameleon
hashing and signatures without key exposure are presented, while
in the setting of gap Diffile-Hellman groups with pairings.
\indent \,\, In this paper, we propose the first key-exposure free
chameleon hash and signature scheme based on discrete logarithm
systems, without using the gap Diffile-Hellman groups. This
provides more flexible constructions of efficient key-exposure
free chameleon hash and signature schemes. Moreover, one
distinguishing advantage of the resulting chameleon signature
scheme is that the property of ``message hiding or ``message
recovery can be achieved freely by the signer, the signer
can efficiently prove which message was the original one if he
desires
Identity-Based Chameleon Hash Scheme Without Key Exposure
In this paper, we propose the first identity-based chameleon hash
scheme without key exposure, which gives a positive answer for the open problem introduced by Ateniese and de Medeiros in 2004
VSH, an efficient and provable collision-resistant hash function
We introduce VSH, very smooth hash, a new S-bit hash function that is provably collision-resistant assuming the hardness of finding nontrivial modular square roots of very smooth numbers modulo an S-bit composite. By very smooth, we mean that the smoothness bound is some fixed polynomial function of S. We argue that finding collisions for VSH has the same asymptotic complexity as factoring using the Number Field Sieve factoring algorithm, i.e., subexponential in S. VSH is theoretically pleasing because it requires just a single multiplication modulo the S-bit composite per ω(5) message-bits (as opposed to O(log S) message-bits for previous provably secure hashes). It is relatively practical. A preliminary implementation on a 1GHz Pentium III processor that achieves collision resistance at least equivalent to the difficulty of factoring a 1024-bit USA modulus, runs at 1.1 MegaByte per second, with a moderate slowdown to 0.7MB/s for 2048-bit RSA security. VSH can be used to build a fast, provably secure randomised trapdoor hash function, which can be applied to speed up provably secure signature schemes (such as Cramer-Shoup) and designated-verifier signatures. © International Association for Cryptologic Research 2006