Consider the well-known oracle attack: Somehow one gets a certain computation result as a function of a secret key from the secret key owner and tries to extract some information on the secret key. This attacking scenario is well understood in the cryptographic community. However, there are many protocols based on the discrete logarithm problem that turn out to leak many of the secret key bits ...

We present an efficient authenticated and fault-tolerant protocol (AFTD) for tree-based key agreement. Our approach is driven by the insight that when a Diffie-Hellman blinded key is updated, in a tree-based method, it suffices to send the update to a small subset of the group, instead of entire group, as current methods require. Our scheme distributes each updated public key to a relatively sm...

Key establishment is the process whereby two or more parties derive a shared secret, typically used for subsequent confidential communication. However, identifying the exact security requirements for key establishment protocols is a nontrivial task. This thesis compares, extends and merges existing security definitions and models for key establishment protocols. The primary focus is on two-part...

The continuous variable quantum key distribution has been considered to have the potential to provide high secret key rate. However, in present experimental demonstrations, the secret key can be distilled only under very small loss rates. Here, by calculating explicitly the computational complexity with the channel transmission, we show that under high loss rate it is hard to distill the secret...

Group key protocols are still an important research issue in the network security, generation and sharing the secret session key is the important factor during the the groupkey transfer protocols. Usually it will be taken care of KGC. KGC encrypts session keys under another secret key shared with each entity during registration. In this paper, we propose an authenticated key transfer protocol b...

Securely sharing the same secret key among multiple parties is the main concern in symmetric cryptography that is the workhorse of modern cryptography due to its simplicity and fast speed. Typically asymmetric cryptography is used to set up a shared secret between parties, after which the switch to symmetric cryptography can be made. In this paper, we introduce a novel key exchange protocol bas...

It has been said that quantum cryptography in general o ers a secure solution to the problem of key enhancement This means that two parties who already share a small secret key can use quantum protocols to establish a new large secret key This large secret key can be arbitrarily long and is unbreakable Thus to date the main contribution of quantum cryptography has been believed to be quan tum k...

Secret sharing schemes protect secrecy and integrity of information by dividing it into shares and distributing these shares among different locations. In k + 1 out of n threshold schemes, security is assured if throughout the entire life-time of the secret the adversary compromises no more than k of the n locations. For long-lived and sensitive secrets this protection may be insufficient. We p...

Consider a CIA agent who wants to authenticate herself to a server, but does not want to reveal her CIA credentials unless the server is a genuine CIA outlet. Consider also that the CIA server does not want to reveal its CIA credentials to anyone but CIA agents – not even to other CIA servers. In this paper we first show how pairing-based cryptography can be used to implement such secret handsh...