This paper focuses on the instantiation of random oracles in public key encryption schemes. A misunderstanding in the former instantiations is pointed out and analyzed. A method of using this primitive as a substituti...This paper focuses on the instantiation of random oracles in public key encryption schemes. A misunderstanding in the former instantiations is pointed out and analyzed. A method of using this primitive as a substitution of random oracles is also proposed. The partial and full instantiations of random oracles in optimal asymmetric encryption padding （OAEP） implemented by pseudorandom functions are described and the resulted schemes are proven to be indistinguishable secure against adaptive chosen ciphertext attack （IND-CCA2） secure. Using this method, one can transform a practical public key encryption scheme secure in the random oracle model into a standard-model secure scheme. The security of the scheme is based on computational assumptions, which is weaker than decisional assumptions used in Cramer- Shoup like schemes.展开更多
This paper formally discusses the security problem caused by the ciphertext verification, presenting a new security notion named IND-CVA （indistinguishability under ciphertext verification attacks） to characterize t...This paper formally discusses the security problem caused by the ciphertext verification, presenting a new security notion named IND-CVA （indistinguishability under ciphertext verification attacks） to characterize the privacy of encryption schemes in this situation. Allowing the adversary to access to both encryption oracle and ciphertext verification oracle, the new notion IND-CVA is slightly stronger than IND-CPA （indistinguishability under chosen-plaintext attacks） but much weaker than IND-CCA （indistin- guishability under chosen-ciphertext attacks）, and can be satisfied by most of the popular symmetric encryption schemes such as OTP （one-time-pad）, CBC （cipher block chaining） and CTR （counter）. An MAC （message authentication scheme） is usually combined with an encryption to guarantee secure communication （e.g. SSH, SSL and IPSec）. However, with the notion of IND-CVA, this paper shows that a secure MAC can spoil the privacy in some cases.展开更多
The scheme introduced by Hwang and Liu in 2008 is shown to be insecure against the key re- placement attack. A more practical attack model is introduced, and according to this model, an efficient cer- tificateless enc...The scheme introduced by Hwang and Liu in 2008 is shown to be insecure against the key re- placement attack. A more practical attack model is introduced, and according to this model, an efficient cer- tificateless encryption scheme is presented which is IND-CCA secure against both Type I and Type II at- tackers without random oracle. This encryption scheme can defend against the malicious key generation center attack, and can reach Girault＇s trusted level 3 as in traditional public key infrastructure-based cryp- tography. This certificateless encryption scheme has a shorter public key than other schemes in the stan- dard model.展开更多
基金Supported by the National Basic Research Program of China (973 Program) (2007CB311201)the National High-Technology Research and Development Program of China (863 Program) (2006AA01Z427)the National Natural Science Foundation of China (60673073)
文摘This paper focuses on the instantiation of random oracles in public key encryption schemes. A misunderstanding in the former instantiations is pointed out and analyzed. A method of using this primitive as a substitution of random oracles is also proposed. The partial and full instantiations of random oracles in optimal asymmetric encryption padding （OAEP） implemented by pseudorandom functions are described and the resulted schemes are proven to be indistinguishable secure against adaptive chosen ciphertext attack （IND-CCA2） secure. Using this method, one can transform a practical public key encryption scheme secure in the random oracle model into a standard-model secure scheme. The security of the scheme is based on computational assumptions, which is weaker than decisional assumptions used in Cramer- Shoup like schemes.
基金the National Basic Research Program of China (Grant No. G2002cb312205)
文摘This paper formally discusses the security problem caused by the ciphertext verification, presenting a new security notion named IND-CVA （indistinguishability under ciphertext verification attacks） to characterize the privacy of encryption schemes in this situation. Allowing the adversary to access to both encryption oracle and ciphertext verification oracle, the new notion IND-CVA is slightly stronger than IND-CPA （indistinguishability under chosen-plaintext attacks） but much weaker than IND-CCA （indistin- guishability under chosen-ciphertext attacks）, and can be satisfied by most of the popular symmetric encryption schemes such as OTP （one-time-pad）, CBC （cipher block chaining） and CTR （counter）. An MAC （message authentication scheme） is usually combined with an encryption to guarantee secure communication （e.g. SSH, SSL and IPSec）. However, with the notion of IND-CVA, this paper shows that a secure MAC can spoil the privacy in some cases.
基金Supported by the National Key Basic Research and Development (973) Program of China (No. 2007CB807902)the National Natural Science Foundation of China (Nos. 90604036 and 60525201)
文摘The scheme introduced by Hwang and Liu in 2008 is shown to be insecure against the key re- placement attack. A more practical attack model is introduced, and according to this model, an efficient cer- tificateless encryption scheme is presented which is IND-CCA secure against both Type I and Type II at- tackers without random oracle. This encryption scheme can defend against the malicious key generation center attack, and can reach Girault＇s trusted level 3 as in traditional public key infrastructure-based cryp- tography. This certificateless encryption scheme has a shorter public key than other schemes in the stan- dard model.
