Key Isolation Study Of Digital Signatures

This thesis introduces the present situation of key-isolation mechanism and finds the following shortcomings by analyzing the present key-isolated digital signatures:1. Now most key-isolated signatures are all signal signature, in other words, in this system, the user participating the sign operation is only one, which doesn’t consider that sometimes there are many users who will sign the message.2. Most of the existing identity-based key-isolated signatures all assume that the key of the peripheral device is absolutely safe and in these systems there is only one peripheral device, which can not meet the actual demand.To solve the above problems, this thesis proposes two different key-isolated signatures and has finished the following work:1. Using the key-isolation mechanism in multiple signatures, a strong (t, N) key-isolated signature is proposed. This scheme not only has the characteristic of multiple signatures, but also has the advantage of strong key-isolation security and short signature length, which can meet a variety of practical applications well.2. There is only one peripheral device in the additional identity-based key-isolated signatures, so the key of the peripheral device is easier to be exposed. Considering this, this thesis proposed a new scheme. In this scheme, there are n different and independent peripheral devices which share the key evolutionary information by the way of (k, n) secret sharing. Any k of these n peripheral devices can help the user update its temporary private key. So even if the private key is updated frequently, this scheme still can maintain lower key exposure probability of peripheral devices, which enhances the ability of system resisting the key exposure.