Exposure of secret keys seems to be unavoidable. Thus, limiting their impact is extremely important. To resolve this problem, the notion of forward security was proposed [4], and the forward security was synthesized into the most powerful notion intrusion-resilience [10, 11]. In intrusion-resilient scheme, time is divided into predefined time periods; each signature includes the number of the time period in which it was generated; the public key remains fixed throughout the lifetime of the protocol but the secret key is periodically updated. Also, secret information is stored by both a user and a base; the user generates signatures on his own, and the base is needed only to help update the user's key from one period to the next. Intrusion-resilient schemes remain secure even after multiple compromises of both the user and the base, as long as they are not both compromised simultaneously. Furthermore, in case the user and base are compromised simultaneously, prior time periods remain secure as in forward-secure scheme.
Intrusion-resilient signature schemes have been previously constructed [8, 10, 11]. Here, we construct a forward-security signature scheme based on the GDH groups, and give the first construction of an intrusion-resilient signature scheme based on the GDH groups.
본 논문에서는 GDH 군에 기반한 새로운 intrusion-resilient 서명 기법을 제안하였다. 비밀키의 노출은 피할 수 없는 문제이고, 이에 따른 피해를 최소화하기 위해서 나온 개념이 forward-security 스킴이다. 여러 가지 방법들이 제시되었고, 최근에는 forward-security 를 변형시킨 더 안전한 intrusion-resilient 서명 기법이 제안되었다. 본문에서는 이를 바탕으로 먼저 겹선형 성질을 갖는 페어링을 이용할 수 있는 GDH 군을 기반으로 한 forward-secure 서명 기법을 제안하고 그 안정성을 증명하였고, 이를 intrusion-resilient 서명 기법으로 확장시켜 제안하였다.
