Revision #2 Authors: Ronald Cramer, Victor Shoup

Accepted on: 12th December 2001 00:00

Downloads: 1281

Keywords:

We present several new and fairly practical public-key encryption

schemes and prove them secure against

adaptive chosen ciphertext attack. One scheme is based on Paillier's

Decision Composite Residuosity (DCR) assumption,

while another is based in the classical Quadratic Residuosity (QR)

assumption. The analysis is in the standard cryptographic

model, i.e., the security of our schemes does not rely on the Random

Oracle model.

We also introduce the notion of a universal hash proof system.

Essentially, this is a special kind of non-interactive

zero-knowledge proof system for an NP language. We do not show that

universal hash proof systems exist for all NP

languages, but we do show how to construct very efficient universal

hash proof systems for a general class of

group-theoretic language membership problems.

Given an efficient universal hash proof system for a language with

certain natural cryptographic indistinguishability

properties, we show how to construct an efficient public-key encryption schemes secure against adaptive chosen ciphertext

attack in the standard model. Our construction only uses the universal

hash proof systemas a primitive: no other primitives

are required, although even more efficient encryption schemes can be

obtained by using hash functions with appropriate

collision-resistance properties. We show how to construct efficient

universal hash proof systems for languages related to

the DCR and QR assumptions. From these we get corresponding public-key

encryption schemes that are secure under these

assumptions. We also show that the Cramer-Shoup encryption scheme

(which up until now was the only practical

encryption scheme that could be proved secure against adaptive chosen

ciphertext attack under a reasonable assumption,

namely, the Decision Diffie-Hellman assumption) is also a special case

of our general theory.

Revision #1 Authors: Ronald Cramer, Victor Shoup, Victor Shoup

Accepted on: 12th December 2001 00:00

Downloads: 1186

Keywords:

TR01-072 Authors: Ronald Cramer, Victor Shoup

Publication: 25th October 2001 00:06

Downloads: 1257

Keywords:

We present several new and fairly practical public-key encryption

schemes and prove them secure against

adaptive chosen ciphertext attack. One scheme is based on Paillier's

Decision Composite Residuosity (DCR) assumption,

while another is based in the classical Quadratic Residuosity (QR)

assumption. The analysis is in the standard cryptographic

model, i.e., the security of our schemes does not rely on the Random

Oracle model.

We also introduce the notion of a universal hash proof system.

Essentially, this is a special kind of non-interactive

zero-knowledge proof system for an NP language. We do not show that

universal hash proof systems exist for all NP

languages, but we do show how to construct very efficient universal

hash proof systems for a general class of

group-theoretic language membership problems.

Given an efficient universal hash proof system for a language with

certain natural cryptographic indistinguishability

properties, we show how to construct an efficient public-key encryption schemes secure against adaptive chosen ciphertext

attack in the standard model. Our construction only uses the universal

hash proof systemas a primitive: no other primitives

are required, although even more efficient encryption schemes can be

obtained by using hash functions with appropriate

collision-resistance properties. We show how to construct efficient

universal hash proof systems for languages related to

the DCR and QR assumptions. From these we get corresponding public-key

encryption schemes that are secure under these

assumptions. We also show that the Cramer-Shoup encryption scheme

(which up until now was the only practical

encryption scheme that could be proved secure against adaptive chosen

ciphertext attack under a reasonable assumption,

namely, the Decision Diffie-Hellman assumption) is also a special case

of our general theory.