Konstantinos Chalkias

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The vast majority of computer and communication systems use passwords in order to identify users. Unfortunately, in ubiquitous alphanumeric password schemes, users tend to choose passwords with predictable characteristics, related to how easy they are to remember. To overcome the vulnerabilities of textual passwords, a lot of alternative techniques have(More)
We revisit the problem of " sending information into the future " by proposing an anonymous, non-interactive, server-based Timed-Release Encryp-tion (TRE) protocol. We improve upon recent approaches by Blake and Chan, Hwang et al., and Cathalo et al., by reducing the number of bilinear pairings that users must compute, and by enabling additional(More)
We propose a new Timed Release Cryptography (TRC) scheme which is based on bilinear pairings together with an S/Key-like procedure used for private key generation. Existing schemes for this task, such as time-lock puzzle approach, provide an approximate release time, dependent on the recipients' CPU speed and the beginning time of the decryption process.(More)
We propose a new server-based efficient protocol for time-release encryption (TRE), or - as sometimes referred to - sending information "into the future". As with other recently-proposed schemes, ours is based on the use of bilinear pairings on any Gap Diffie-Hellman group, allowing absolute release time of the encrypted data. Our protocol possesses the(More)
Hadoop is a fault tolerant Java framework that supports data distribution and process parallelization using commodity hardware. Based on the provided scalability and the independence of task execution, we combined Hadoop with crawling techniques to implement various applications that deal with large amount of data. Our experiments show that Hadoop is a very(More)
For two parties to communicate securely over an insecure channel, they must be able to authenticate one another and establish a common session key. We propose a new secure one-pass authenticated key establishment protocol which is well suited to one-way communication channels. The protocol is examined using an extension of the Bellare-Rogaway model proposed(More)
Key establishment protocols are among the most important security mechanisms via which two or more parties can generate a common session key to in order to encrypt their communications over an otherwise insecure network. This paper is concerned with the vulnerability of one-pass two-party key establishment protocols to key-compromise impersonation (K-CI)(More)
Identity Based Encryption (IBE) constitutes an alternative cryptographic method to the conventional public key systems. The main feature of IBE is that public keys are not transmitted over the network, but they are efficiently computed from the receivers’ unique identity information; thus, the system is certificateless. This paper presents a(More)
There are nowdays various e-business applications, such as sealed-bid auctions and electronic voting, that require time-delayed decryp-tion of encrypted data. The literature offers at least three main categories of protocols that provide such timed-release encryption (TRE). They rely either on forcing the recipient of a message to solve some time-consuming,(More)