In this paper, we first propose a tripletrapdoor chameleon hash function. Foreword this is a set of lecture notes on cryptography compiled for 6. A file protection system based on a trapdoor oneway hash. This video gives a motivation and a general idea about the concept of oneway function in cryptography.
Lossy trapdoor functions were used to build the rst injective trapdoor functions based on ddh, the rst indcca cryptosystems based on lattice assumptions, and they are known to imply deterministic encryption, collision resistant hashfunctions, oblivious transfer and a host of other important primitives. The fastest algorithm for computing partial collisions is brute force. Inouropinion, the proposed protocol which does not require the precomputed value of 1 dynamically provides the security against di erent attacks, even when new nodes are added to the. This is similar to elgamals signature scheme 15 in which a onetime secret key was introduced for signing each message. Srilatha web based services engage distribution of contents like digital audio, video, games, software, stock quotes, streaming presentations and live news feeds throughout distributed networking technologies, like content distribution networks cdns, multicast networks, and. Yes, a trapdoor oneway function is a primitive from which one can build an asymmetric cryptosystem. Trapdoor hash functions and their applications request pdf. Dual projective hashing and its applications lossy. Trapdoor hash functions have been considered before see e. Each cooperator can modify the document in realtime and view the other cooperators. Different from other hash functions, trapdoor hash function is a probability function with the hash key and the trapdoor key.
The secret signing key is guaranteed to be hidden from the signatures, since the signatures are produced from a trapdoorindependent distribution. Motivated by the use of the double trapdoor chameleon hash function by chen et al. Research article an access control protocol for wireless. Dual projective hashing and its applications lossy trapdoor functions and more hoeteck wee. Finally, an mthbased aggregate signature scheme mthas with constant signature length is proposed. A dictionary is a set of strings and we can define a hash function as follows. A trapdoor function is a function that is easy to compute in one direction, yet believed to be difficult to compute in the opposite direction finding its inverse without special information, called the trapdoor. Some trapdoor hash functions 3, 11 have been pro posed to economize on the online computation when gen erating signature. This is both a theoretical drawback and also a practical concern see, e. Improvement on a trapdoor hash function semantic scholar.
We realize lossy tdfs under a variety of different numbertheoretic assumptions, including hardness. One tempting approach is to encrypt the functions random input x using x itself as the. Pdf chameleonhashes with ephemeral trapdoors researchgate. And i wouldnt count this as a hash, as it is not completely deterministic. This standard for secretkey systems arose around 1970. Chameleon hash was introduced by krawczyk and rabin 20 as a tool to construct chameleon signatures.
This is similar to cramershoup projective hashing, except that instead of smoothness, which stipulates that the output of the hash function. That is, we introduce a new parameter r for our proposed trapdoor hash function, and denote h hkm,r,s as a trapdoor hash function in h. Request pdf trapdoor hash functions and their applications we introduce a new primitive, called trapdoor hash functions tdh, which are hash functions \\mathsf h. The public hash key is, and the private trapdoor key is. This primitive opens a floodgate of applications for lowcommunication secure computation. An access control protocol for wireless sensor network. These signature schemes form an essential part of the collection of mechanisms used for securing todays computing systems. We introduce the notion of dual projective hashing. Secondly, the multitrapdoor hash function mth based on dth is presented. Chameleonhash functions, also called trapdoorhash functions, are hash functions that feature a trapdoor that allows one to find arbitrary collisions in the domain. For the given hash family, we define the hash key and the proposed chameleon hash function as follows. We mainly focus on twomessage protocols between a receiver and a sender, with private inputs x and y, resp. Building lossy trapdoor functions from lossy encryption.
Approximate trapdoors for lattices and smaller hashand. Stream authentication using trapdoor hash function dodla padmaja1, p. In this work, we show that if enc is a lossy encryption with messages at least 1bit longer than randomness, and h is a pairwise independent hash function, then x 7. Informally, a chameleon hash function is a trapdoor collisionresistant hash function. Hash functions, publickey encryption university of chicago. Without the knowledge of the trapdoor key, a trapdoor hash function is collision resistant. Efficient vehicle ownership identification scheme based on.
Pdf trapdoors are widely used in cryptography, in particular for digital signatures and. I is a probabilistic polynomial time key generation algorithm that on input 1 k, outputs a pair hashtrapdoor key, hktk, such that the sizes of hktk, are polynomially related to k. We wish to optimize the download rate of such protocols, namely the asymptotic ratio between the size of the output. Secondly, the multitrapdoor hash function mth based on dth is. Combining these instantiations with our generic transformations, we obtain. Dual projective hashing and its applications lossy trapdoor functions and more 249 in 14, 12 does yield a dual projective hash function, since we can ef. Unlike traditional hash functions, a trapdoor hash function 30 is associated with a public and private key, also called a hash and trapdoor key, respectively. There is no challenge as the client can safely choose his own random challenge, and so the hashcash costfunction is a trapdoorfree and noninteractive costfunction. Cryptography lecture 6 public key principles, oneway.
Trapdoor functions i public function fgenerated with secret trapdoor f 1 i new twist gpv08. Pdf onetime trapdoor oneway functions researchgate. An efficient elliptic curve discrete logarithm based. In a collaborative workflow platform, when a group leader receives a document which requires cooperators support, shehe assigns the task to the cooperators. A double trapdoor chameleon hash function carries the following properties. Goldwasser and mihir bellare in the summers of 19962002, 2004, 2005 and 2008. The cost of computing and storage will be saved since each vo license needs. To tolerate the out of order arrival rates and the transmission losses should be resilient in intermediate blocks without affecting the remaining blocks in the stream. Authentication of online digitized content using trapdoor. Trapdoor hash function is a highly useful cryptographic primitive for building a wide variety of novel signature schemes, like chameleon, onlineoffline, threshold, proxy, sanitizable and amortized signatures.
Despite its elegant design, the hashandsign signature based on ajtais function suffers from prac. We introduce a new primitive, called trapdoor hash functions tdh, which are hash func tions h. Suppose we need to store a dictionary in a hash table. Onetime trapdoor oneway functions ucl computer science. Hash functions are not macs both map long inputs to short outputs but a hash function does not take a key. Firstly, to prevent key exposition, based on the elliptic curve discrete logarithm problem ecdlp, we constructed a double trapdoor hash function dth and proved its reliability.
Based on the tripletrapdoor hash function, we employ the concept of a hashsignswitch paradigm to create the vois. Lossy trapdoor functions were introduced by peikert and waters 34, who showed that they imply fundamental cryptographic primitives such as trapdoor functions, collisionresistant hash functions, oblivious transfer, and ccasecure publickey encryption. Pdf efficient platform for traceable collaborative. When both tk and hk are known, it is easy to calculate the trapdoor collision. The primary motivation of our study is to improve the ef. There is no challenge as the client can safely choose his own random challenge, and so the hashcash cost function is a trapdoor free and noninteractive cost function. An introduction to multitrapdoor hash functions and its.
Universal oneway hash functions and their cryptographic. Trapdoor hash functions and their applications springerlink. A oneway function is similar to a trapdoor function in that its easy to compute both and its very hard to reverse both, but there is no special. Finding a good hash function it is difficult to find a perfect hash function, that is a function that has no collisions.
Previously, all provably secure signature schemes were based on the stronger mathematical assumption that trapdoor oneway functions exist. Stream authentication using trapdoor hash function dodla padmaja, p. Lncs 7237 dual projective hashing and its applications. Pdf a chameleonhash function is a hash function that involves a trapdoor the knowledge of which allows one to find arbitrary collisions in the. The concept of function is defined and some example. Given a hash key pair and a pair, is computable in the polynomial time. Rather than generating additional lists randomly, he proposed to use the hash function on each element of that initial secret key, in order to derive the next such list for the secret key. It is a modification of the doubletrapdoor hash function chen et al. Trapdoor hash functions and their applications nico dottling sanjam gargy yuval ishaiz giulio malavolta tamer mour rafail ostrovskyk abstract weintroduceanewprimitive,calledtrapdoor hash functions tdh,whicharehashfunc.
Trapdoor hash functions and their applications cryptology eprint. A hash function is a deterministic function h that reduces arbitrary strings to fixedlength. Tech student, dept of computer science and engineering, anurag group of institution. A hash function is not a trapdoor function because it is not reversible. A file protection system based on a trapdoor oneway hash function chinchen chang1, 3, chuhsing lin2 and jungsan lee3 1department of information engineering and computer science, feng chia university, taichung, taiwan, 40724, r. As a result, they have so far required the random oracle model or similar heuristics for their security analysis. And similarly, one can use the hash function again on that list to get the next list. Trapdoor functions are widely used in cryptography in mathematical terms, if f is a trapdoor function there exists some secret information y, such that given fx and y it is. Chameleonhashes with ephemeral trapdoors cryptology eprint. The collision resistance of the trapdoor hash functions depends on the users knowledge state.
Based on the assumption of ecdlp, the proposed scheme is proven unforgeable against adaptive chosen message attacks with the forking lemma. But we can do better by using hash functions as follows. An aggregate signature scheme based on a trapdoor hash. Only known solution for higher rate uses highrate homomorphic encryption.
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