Seung Choi - Academia.edu (original) (raw)
Uploads
Papers by Seung Choi
Proceedings on Privacy Enhancing Technologies, 2020
We consider a scenario where multiple organizations holding large amounts of sensitive data from ... more We consider a scenario where multiple organizations holding large amounts of sensitive data from their users wish to compute aggregate statistics on this data while protecting the privacy of individual users. To support large-scale analytics we investigate how this privacy can be provided for the case of sketching algorithms running in time sub-linear of the input size. We begin with the well-known LogLog sketch for computing the number of unique elements in a data stream. We show that this algorithm already achieves differential privacy (even without adding any noise) when computed using a private hash function by a trusted curator. Next, we show how to eliminate this requirement of a private hash function by injecting a small amount of noise, allowing us to instantiate an efficient LogLog protocol for the multi-party setting. To demonstrate the practicality of this approach, we run extensive experimentation on multiple data sets, including the publicly available IP address data se...
Theory of Cryptography, 2014
We continue the line of work initiated by Katz (Eurocrypt 2007) on using tamper-proof hardware fo... more We continue the line of work initiated by Katz (Eurocrypt 2007) on using tamper-proof hardware for universally composable secure computation. As our main result, we show an efficient oblivious-transfer (OT) protocol in which two parties each create and exchange a single, stateless token and can then run an unbounded number of OTs. Our result yields what we believe is the most practical and efficient known approach for oblivious transfer based on tamper-proof tokens, and implies that the parties can perform (repeated) secure computation of arbitrary functions without exchanging additional tokens. Motivated by this result, we investigate the minimal number of stateless tokens needed for universally composable OT/ secure computation. We prove that our protocol is optimal in this regard for constructions making black-box use of the tokens (in a sense we define). We also show that nonblack-box techniques can be used to obtain a construction using only a single stateless token.
Proceedings of the 2021 ACM SIGSAC Conference on Computer and Communications Security, 2021
Fully homomorphic encryption (FHE) enables a simple, attractive framework for secure search. Comp... more Fully homomorphic encryption (FHE) enables a simple, attractive framework for secure search. Compared to other secure search systems, no costly setup procedure is necessary; it is sufficient for the client merely to upload the encrypted database to the server. Confidentiality is provided because the server works only on the encrypted query and records. While the search functionality is enabled by the full homomorphism of the encryption scheme. For this reason, researchers have been paying increasing attention to this problem. Since Akavia et al. (CCS 2018) presented a framework for secure search on FHE encrypted data and gave a working implementation called SPiRiT, several more efficient realizations have been proposed. In this paper, we identify the main bottlenecks of this framework and show how to significantly improve the performance of FHEbase secure search. In particular, • To retrieve ℓ matching items, the existing framework needs to repeat the protocol ℓ times sequentially. In our new framework, all matching items are retrieved in parallel in a single protocol execution. • The most recent work by Wren et al. (CCS 2020) requires O(n) multiplications to compute the first matching index. Our solution requires no homomorphic multiplication, instead using only additions and scalar multiplications to encode all matching indices. • Our implementation and experiments show that to fetch 16 matching records, our system gives an 1800X speed-up over the state of the art in fetching the query results resulting in a 26X speed-up for the full search functionality. CCS CONCEPTS • Theory of computation → Cryptographic protocols; • Security and privacy → Management and querying of encrypted data; Cryptography.
Proceedings on Privacy Enhancing Technologies, 2020
We consider a scenario where multiple organizations holding large amounts of sensitive data from ... more We consider a scenario where multiple organizations holding large amounts of sensitive data from their users wish to compute aggregate statistics on this data while protecting the privacy of individual users. To support large-scale analytics we investigate how this privacy can be provided for the case of sketching algorithms running in time sub-linear of the input size. We begin with the well-known LogLog sketch for computing the number of unique elements in a data stream. We show that this algorithm already achieves differential privacy (even without adding any noise) when computed using a private hash function by a trusted curator. Next, we show how to eliminate this requirement of a private hash function by injecting a small amount of noise, allowing us to instantiate an efficient LogLog protocol for the multi-party setting. To demonstrate the practicality of this approach, we run extensive experimentation on multiple data sets, including the publicly available IP address data se...
Theory of Cryptography, 2014
We continue the line of work initiated by Katz (Eurocrypt 2007) on using tamper-proof hardware fo... more We continue the line of work initiated by Katz (Eurocrypt 2007) on using tamper-proof hardware for universally composable secure computation. As our main result, we show an efficient oblivious-transfer (OT) protocol in which two parties each create and exchange a single, stateless token and can then run an unbounded number of OTs. Our result yields what we believe is the most practical and efficient known approach for oblivious transfer based on tamper-proof tokens, and implies that the parties can perform (repeated) secure computation of arbitrary functions without exchanging additional tokens. Motivated by this result, we investigate the minimal number of stateless tokens needed for universally composable OT/ secure computation. We prove that our protocol is optimal in this regard for constructions making black-box use of the tokens (in a sense we define). We also show that nonblack-box techniques can be used to obtain a construction using only a single stateless token.
Proceedings of the 2021 ACM SIGSAC Conference on Computer and Communications Security, 2021
Fully homomorphic encryption (FHE) enables a simple, attractive framework for secure search. Comp... more Fully homomorphic encryption (FHE) enables a simple, attractive framework for secure search. Compared to other secure search systems, no costly setup procedure is necessary; it is sufficient for the client merely to upload the encrypted database to the server. Confidentiality is provided because the server works only on the encrypted query and records. While the search functionality is enabled by the full homomorphism of the encryption scheme. For this reason, researchers have been paying increasing attention to this problem. Since Akavia et al. (CCS 2018) presented a framework for secure search on FHE encrypted data and gave a working implementation called SPiRiT, several more efficient realizations have been proposed. In this paper, we identify the main bottlenecks of this framework and show how to significantly improve the performance of FHEbase secure search. In particular, • To retrieve ℓ matching items, the existing framework needs to repeat the protocol ℓ times sequentially. In our new framework, all matching items are retrieved in parallel in a single protocol execution. • The most recent work by Wren et al. (CCS 2020) requires O(n) multiplications to compute the first matching index. Our solution requires no homomorphic multiplication, instead using only additions and scalar multiplications to encode all matching indices. • Our implementation and experiments show that to fetch 16 matching records, our system gives an 1800X speed-up over the state of the art in fetching the query results resulting in a 26X speed-up for the full search functionality. CCS CONCEPTS • Theory of computation → Cryptographic protocols; • Security and privacy → Management and querying of encrypted data; Cryptography.