International Association for Cryptologic Research

International Association
for Cryptologic Research

CryptoDB

Dong Hoon Lee

Affiliation: CIST, Korea University

Publications

Year
Venue
Title
2018
TCHES
FACE: Fast AES CTR mode Encryption Techniques based on the Reuse of Repetitive Data
Jin Hyung Park Dong Hoon Lee
The Advanced Encryption Standard (AES) algorithm and Counter (CTR) mode are used for numerous services as an encryption technique that provides confidentiality. Even though the AES with counter (AES CTR) mode has an advantage in that it can process multiple data blocks in parallel, its implementation should also be observed to reduce the computational burden of current services.In this paper, we propose an implementation method called FACE that can improve the performance of the AES CTR mode. The proposed method is based on five caches of frequently occurring intermediate values, so that it reduces the number of unnecessary computations. Our method can be employed in any AES CTR implementation, regardless of the platform, environment, or implementation method. There are two known AES implementation techniques, namely, counter-mode caching and bitslicing. FACE extends counter-mode caching in order to optimize the previous result and to maximize the scope of caching. We show that FACE can be applied efficiently to various implementations (table-based, bitsliced, and AES-NI-based). In particular, this is the first attempt to combine our extended counter-mode caching with bitsliced implementations of AES, and is also the first to apply counter-mode caching up to the round transformations of AES-NI implementation. To prove the efficiency of our proposed method, we conduct a performance evaluation in various environments, which we then compare with the previous fastest results. Our bitsliced FACE needs 6.41 cycles/byte on an Intel Core 2, and AES-NI-based FACE records 0.44 cycles/byte on an Intel Core i7.
2015
EPRINT
2014
EPRINT
2014
EPRINT
2013
PKC
2013
ASIACRYPT
2007
EPRINT
Secure Similarity Search
One of the most substantial ways to protect users' sensitive information is encryption. This paper is about the keyword index search system on encrypted documents. It has been thought that the search with errors over encrypted data is impossible because 1 bit difference over plaintexts may reduce to enormous bits difference over cyphertexts. We propose a novel idea to deal with the search with errors over encrypted data. We develop two similarity search schemes, implement the prototypes and provide substantial analysis. We define security requirements for the similarity search over encrypted data. The first scheme can achieve perfect privacy in similarity search but the second scheme is more efficient.
2006
EPRINT
Searchable Index Schemes for Groups : Security vs. Efficiency
Hyun-A Park Yu Jeong Lee Dong Hoon Lee
A secure index search protocol makes it possible to search for the index of encrypted documents using specified keywords without decrypting them. %An untrusted database manager learns nothing more %than the search result about the documents without revealing the %keyword. These days, personally portable devices of huge storage such as a USB are easily used and hence private and sensitive documents of a user may be securely kept in such personal devices. However, secret documents shared by groups are usually stored in database. In real organizations such as government offices or enterprises with many departments, a group search occurs more often. In this paper, we propose two search schemes for a hierarchical group under an untrusted server ; A security-centered search scheme(SSIS) and an optimized efficient search scheme(ESIS) for commercial business use. We define `correlation resistance' as privacy requirement over encrypted search system and prove that SSIS can meet the notion. Also, we experimented two our proposed schemes. In the first try, the performance of both schemes was not good to use for practical business use. It was not until examining the reason of this that we learned the efficient DB schema must be applied into the search system for good performance. However, it was hard to apply efficient DB schema into SSIS because of its data structure. Hence, we applied efficient DB schema into only ESIS. The experiments show that ESIS is approximately 200 times faster than SSIS, which implies that other existing schemes are also not practical because the data structure of them is similar to SSIS. ESIS achieves real practicabilty by loosening its security, but with at least extend. Therefore, in the near future, it's required to develop keyword search system over encrypted data which is secure and applicable to efficient DB schema. In addition, we learned a lesson that works about the efficiency must consider mutual interactive operation with application layer as well as computational efficiency of a proposing scheme.
2006
EPRINT
Password-Authenticated Multi-Party Key Exchange with Different Passwords
Password-authenticated key exchange (PAKE) allows two or multiple parties to share a session key using a human-memorable password only. PAKE has been applied in various environments, especially in the "clientserver" model of remotely accessed systems. Designing a secure PAKE scheme has been a challenging task because of the low entropy of password space and newly recognized attacks in the emerging environments. In this paper, we study PAKE for multi-party with different passwords which allows group users with different passwords to agree on a common session key by the help of a trusted server using their passwords only. In this setting, the users do not share a password between themselves but only with the server. The fundamental security goal of PAKE is security against dictionary attacks. We present the first two provably secure protocols for this problem in the standard model under the DDH assumption; our first protocol is designed to provide forward secrecy and to be secure against known-key attacks. The second protocol is designed to additionally provide key secrecy against curious servers. The protocols require a constant number of rounds.
2005
CRYPTO
2005
EUROCRYPT
2005
EPRINT
Comments on Weaknesses in Two Group Diffie-Hellman Key Exchange Protocols
Jin Wook Byun Dong Hoon Lee
In [3], Tang presented two password guessing attacks such as off-line and undetectable on-line dictionary attacks against password-based group Diffie-Hellman key exchange protocols by Byun and Lee [2]. In this paper, we present countermeasures for two attacks by Tang.
2004
ASIACRYPT
2004
PKC

Program Committees

Asiacrypt 2013
Asiacrypt 2012
Asiacrypt 2011
PKC 2010
Asiacrypt 2010
Asiacrypt 2009
PKC 2006
Asiacrypt 2004