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A practical public key cryptosystem provably secure against adaptive chosen ciphertext attack
 CRYPTO '98
, 1998
"... A new public key cryptosystem is proposed and analyzed. The scheme is quite practical, and is provably secure against adaptive chosen ciphertext attack under standard intractability assumptions. There appears to be no previous cryptosystem in the literature that enjoys both of these properties simu ..."
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Cited by 540 (16 self)
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A new public key cryptosystem is proposed and analyzed. The scheme is quite practical, and is provably secure against adaptive chosen ciphertext attack under standard intractability assumptions. There appears to be no previous cryptosystem in the literature that enjoys both of these properties simultaneously.
The Decision DiffieHellman Problem
, 1998
"... The Decision DiffieHellman assumption (ddh) is a gold mine. It enables one to construct efficient cryptographic systems with strong security properties. In this paper we survey the recent applications of DDH as well as known results regarding its security. We describe some open problems in this are ..."
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Cited by 241 (6 self)
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The Decision DiffieHellman assumption (ddh) is a gold mine. It enables one to construct efficient cryptographic systems with strong security properties. In this paper we survey the recent applications of DDH as well as known results regarding its security. We describe some open problems in this area. 1 Introduction An important goal of cryptography is to pin down the exact complexity assumptions used by cryptographic protocols. Consider the DiffieHellman key exchange protocol [12]: Alice and Bob fix a finite cyclic group G and a generator g. They respectively pick random a; b 2 [1; jGj] and exchange g a ; g b . The secret key is g ab . To totally break the protocol a passive eavesdropper, Eve, must compute the DiffieHellman function defined as: dh g (g a ; g b ) = g ab . We say that the group G satisfies the Computational DiffieHellman assumption (cdh) if no efficient algorithm can compute the function dh g (x; y) in G. Precise definitions are given in the next sectio...
Design and Analysis of Practical PublicKey Encryption Schemes Secure against Adaptive Chosen Ciphertext Attack
 SIAM Journal on Computing
, 2001
"... A new public key encryption scheme, along with several variants, is proposed and analyzed. The scheme and its variants are quite practical, and are proved secure against adaptive chosen ciphertext attack under standard intractability assumptions. These appear to be the first publickey encryption sc ..."
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Cited by 231 (11 self)
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A new public key encryption scheme, along with several variants, is proposed and analyzed. The scheme and its variants are quite practical, and are proved secure against adaptive chosen ciphertext attack under standard intractability assumptions. These appear to be the first publickey encryption schemes in the literature that are simultaneously practical and provably secure.
Securing Threshold Cryptosystems against Chosen Ciphertext Attack
 JOURNAL OF CRYPTOLOGY
, 1998
"... ..."
Using Hash Functions as a Hedge against Chosen Ciphertext Attack
, 2000
"... The cryptosystem recently proposed by Cramer and Shoup [5] is a practical public key cryptosystem that is secure against adaptive chosen ciphertext attack provided the Decisional DiffieHellman assumption is true. Although this is a reasonable intractability assumption, it would be preferable to bas ..."
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Cited by 73 (7 self)
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The cryptosystem recently proposed by Cramer and Shoup [5] is a practical public key cryptosystem that is secure against adaptive chosen ciphertext attack provided the Decisional DiffieHellman assumption is true. Although this is a reasonable intractability assumption, it would be preferable to base a security proof on a weaker assumption, such as the Computational DiffieHellman assumption. Indeed, this cryptosystem in its most basic form is in fact insecure if the Decisional DiffieHellman assumption is false. In this paper we present a practical hybrid scheme that is just as efficient as the scheme of of Cramer and Shoup; we prove that the scheme is secure if the Decisional DiffieHellman assumption is true; we give strong evidence that the scheme is secure if the weaker, Computational DiffieHellman assumption is true by providing a proof of security in the random oracle model.
Security of Signed ElGamal Encryption
 In Asiacrypt ’2000, LNCS 1976
, 2000
"... . Assuming a cryptographically strong cyclic group G of prime order q and a random hash function H, we show that ElGamal encryption with an added Schnorr signature is secure against the adaptive chosen ciphertext attack, in which an attacker can freely use a decryption oracle except for the target c ..."
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Cited by 42 (3 self)
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. Assuming a cryptographically strong cyclic group G of prime order q and a random hash function H, we show that ElGamal encryption with an added Schnorr signature is secure against the adaptive chosen ciphertext attack, in which an attacker can freely use a decryption oracle except for the target ciphertext. We also prove security against the novel onemoredecyption attack. Our security proofs are in a new model, corresponding to a combination of two previously introduced models, the Random Oracle model and the Generic model. The security extends to the distributed threshold version of the scheme. Moreover, we propose a very practical scheme for private information retrieval that is based on blind decryption of ElGamal ciphertexts. 1 Introduction and Summary We analyse a very practical public key cryptosystem in terms of its security against the strong adaptive chosen ciphertext attack (CCA) of [RS92], in which an attacker can access a decryption oracle on arbitrary ciphertexts (ex...
Why Chosen Ciphertext Security Matters
, 1998
"... This article motivates the importance of publickey cryptosystems that are secure against chosen ciphertext attack, and of rigorous security proofs. It also discusses the new cryptosystem developed by Cramer and Shoup, and its relevance in this regard. ..."
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Cited by 36 (2 self)
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This article motivates the importance of publickey cryptosystems that are secure against chosen ciphertext attack, and of rigorous security proofs. It also discusses the new cryptosystem developed by Cramer and Shoup, and its relevance in this regard.
The Classification of Hash Functions
, 1993
"... When we ask what makes a hash function `good', we usually get an answer which includes collision freedom as the main (if not sole) desideratum. However, we show here that given any collisionfree function, we can derive others which are also collisionfree, but cryptographically useless. This e ..."
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Cited by 24 (3 self)
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When we ask what makes a hash function `good', we usually get an answer which includes collision freedom as the main (if not sole) desideratum. However, we show here that given any collisionfree function, we can derive others which are also collisionfree, but cryptographically useless. This explains why researchers have not managed to find many interesting consequences of this property. We also prove Okamoto's conjecture that correlation freedom is strictly stronger than collision freedom. We go on to show that there are actually rather many properties which hash functions may need. Hash functions for use with RSA must be multiplication free, in the sense that one cannot find X , Y and Z such that h(X)h(Y ) = h(Z); and more complex requirements hold for other signature schemes. Universal principles can be proposed from which all the freedom properties follow, but like most theoretical principles, they do not seem to give much value to a designer; at the practical level, the main imp...
Secure Lengthsaving ElGamal Encryption under the Computational DiffieHellman Assumption
 In Proc. 5th Australian Conference on Information, Security, and Privacy
, 2000
"... A design of secure and efficient public key encryption schemes under weaker computational assumptions has been regarded as an important and challenging task. As far as the ElGamaltype encryption is concerned, some variants of the original ElGamal encryption scheme whose security depends on weaker c ..."
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Cited by 14 (2 self)
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A design of secure and efficient public key encryption schemes under weaker computational assumptions has been regarded as an important and challenging task. As far as the ElGamaltype encryption is concerned, some variants of the original ElGamal encryption scheme whose security depends on weaker computational assumption have been proposed: Although the security of the original ElGamal encryption is based on the decisional DiffieHellman assumption (DDHA), the security of a recent scheme, such as Pointcheval's ElGamal encryption variant, is based on the weaker assumption, the computational DiffieHellman assumption (CDHA). In this paper, we propose a lengthsaving ElGamal encryption variant whose security is based on CDHA and analyze its security in the random oracle model. The proposed scheme is lengthefficient which provides a shorter ciphertext than that of Pointcheval's scheme and provably secure against the chosenciphertext attack.
On the security of RSA encryption in TLS
 In Moti Yung, editor, Advances in Cryptology—CRYPTO 2002
, 2002
"... Abstract. We show that the security of the TLS handshake protocol based on RSA can be related to the hardness of inverting RSA given a certain “partialRSA ” decision oracle. The reduction takes place in a security model with reasonable assumptions on the underlying TLS pseudorandom function, there ..."
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Cited by 8 (0 self)
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Abstract. We show that the security of the TLS handshake protocol based on RSA can be related to the hardness of inverting RSA given a certain “partialRSA ” decision oracle. The reduction takes place in a security model with reasonable assumptions on the underlying TLS pseudorandom function, thereby addressing concerns about its construction in terms of two hash functions. The result is extended to a wide class of constructions that we denote tagged keyencapsulation mechanisms. Keywords: key encapsulation, RSA encryption, TLS. 1