Ricardo Felipe Custódio

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Farnel is a voting system proposed in 2001 in which each voter signs a ballot. It uses two ballot boxes to avoid the association between a voter and a vote. In this paper we first point out a flaw in the ThreeBallot system proposed by Rivest that seems to have gone unnoticed so far: it reveals statistical information about who is winning the election. Then,(More)
Timed release of confidential information, where information is revealed at the date and time established by the author, is a security requirement in applications such as auctions, wills, and government buying processes. We have found that this security requirement is achieved through the fulfillment of a group of requirements that are not completely(More)
The timing behavior of the EDCA mechanism defined in the IEEE 802.11e standard is analyzed. More specifically, the target of this paper is to evaluate the limitations of the highest priority level of the EDCA mechanism (voice category) when supporting real-time (RT) communication. By RT communication, we mean small-sized packets generated in periodic(More)
The private keys used in a PKI are its most important asset. Protect these keys from unauthorised use or disclosure is essential to secure a PKI. Relying parties need assurances that the private key used to sign their certificates is controlled and managed following pre-defined statement policy. Hardware Security Modules (HSM) offer physical and logical(More)
Hardware Security Modules (HSMs) are an useful tool to deploy public key infrastructure (PKI) and its applications. This paper presents necessary procedures and protocols to perform backup and audit in such devices when deployed in PKIs. These protocols were evaluated in an implementation of a real HSM, enabling it to perform secure backups and to provide(More)
We propose a new Public Key Infrastructure model for long-term signatures. It is based on X.509 and the real world of handwritten signatures. In the model, notaries certify that a signer's certificate is trustworthy to verify a particular signature at a specific time. An end user issues his own X.509 certificate, whose validity period is meaningless and(More)
—Ceremonies are a useful tool to establish trust in scenarios where protocols operate. They describe a greater range of issues not taken into account by protocol designers. We take an already-designed protocol and ceremony for a key management protocol operating in a Public-Key Infrastructure environment and test it using a formal method. The ceremonies(More)
Secure archiving of authenticated and sensitive documents is becoming a necessity due to the dematerialization of paper based documents and processes. Huhnlein et al. combined the Open Archival Information System (OAIS) Reference Model, Evidence Record Syntax (ERS) with Secret Sharing and proposed the Comprehensive Reference Architecture for Trustworthy(More)