1. 1 伺服器輔助秘密運算 機置及其應用 Server-aided Secret Computation -- Schemes and Applications 洪國寶 AI Lab

2. 2 Server-aided Secret Computation Secret computation outsourcing when an entity (the client) needs to execute a task but does not have the appropriate computation power to perform it. The task is then delegated to external servers which have the sufficient calculation power. The main security issue of a secure outsourcing is to delegate a computation to a set of untrusted servers without revealing neither the input nor the output

3. 3 Server-aided Secret Computation The key idea is for the client to do some pre- processing over the input before sending it to the servers, and then to do some post-processing over the servers result to recover the final computation output. There are two main pre-processing methods to hide the secret input: disguise and encryption. –The disguise is to apply some functional or mathematical transformations over the input. –The encryption is a particular disguise method which consists in encrypting the input using a secret key.

4. 4 Server-aided Secret Computation A simple example (for RSA signature scheme)

5. 5 Server-aided Secret Computation

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7. 7 本研究計畫之目的 Our research goals are four-fold: (1) to study basic tools for designing secure computation outsourcing schemes, (2) to design practical server-aided secret computation for exponentiation-based schemes, (3) to design practical server-aided secret computation for elliptic-curve-based schemes, and (4) to design and implement practical building blocks for realizing CaaS (cryptography as a (ubicomp) service).

8. 8 Construct models and study basic tools Model –For security analysis Basic tools – 巧思

9. 9 Design server-aided exponentiation schemes Studied and analyzed basic tools and schemes for server-aided secure exponentiation; Designed new secure server-aided RSA signature generation schemes; and Designed server-aided signature/ certificate/identification verification schemes.

10. 10 Point multiplication based schemes Studied and analyzed basic tools and schemes for server-aided elliptic curve operations; Designed secure server-aided ECDSA and ECDH schemes; Designed server-aided ECDH schemes

11. 11 Pairing-based schemes and applications Designed secure server-aided pairing based applications.

12. 12 Implement server-aided computation Designed building blocks for realizing cryptography as a service; and Designed schemes for supporting email server that accommodates user’s encrypted emails where the server needs to perform user identification and helps user with decryption.

13. 13 Implement server-aided computation Design hardware/software architecture and interface Implement Security Association Negotiation Develop server/client programs

14. 14 Implementation 用於本計畫之實驗設計實作 – 個人數位助理 – 小筆電 –OS, language Query the communication speed, and the computational power of PDA (and/or smart card, mobile phone, etc.) and server (PC, workstation, etc.)