Is it feasible for parties to securely evaluate a function on their joint inputs, while hiding not only their private input, but even the very fact that they are taking part to the protocol? This intriguing question was given a positive answer in the two-party case at STOC’05, and in the general case at FOCS’07, under the name of covert multiparty computation (CMPC). A CMPC protocol allows n pl...

The aim of timestamping systems is to provide a proof-of-existence of a digital document at a given time. By timestamping a digital document after it has been signed by concerned parties, we know when the document was signed. Timestamping services also provide the non-repudiation and long term properties for digital signatures. Combining both digital signature and provable timestamping guarante...

Consider a scenario in which parties use a public key encryption scheme and a signature scheme with a single public key/private key pair—so the private key sk is used for both signing and decrypting. Such a simultaneous use of a key is in general considered poor cryptographic practice, but from an efficiency point of view looks attractive. We offer security notions to analyze such violations of...

We present a novel hybrid communication protocol that guarantees mobile users’ k-anonymity against a wide-range of adversaries by exploiting the capability of handheld devices to connect to both WiFi and cellular networks. Unlike existing anonymity schemes, we consider all parties that can intercept communications between the mobile user and a server as potential privacy threats. We formally qu...

OVERVIEW OF FRANCE F rance is an industrialized country with a large agricultural sector. Its population in 1991 totaled 57 million. According to the Constitution of 1958, France is organized as a parliamentary democratic republic. Separation of legislative and executive powers, multiplicity of political parties, and respect for the Constitution and the Human Rights Declaration are the guaranti...

We present a generic method for turning passively secure protocols into protocols secure against covert attacks. The method adds a post-execution verification phase to the protocol that allows a misbehaving party to escape detection only with negligible probability. The execution phase, after which the computed protocol result is already available for parties, has only negligible overhead added...

Verifiable Secret Sharing (VSS) guarantees that honest parties reconstruct a consistent secret even in the presence of a malicious dealer that distributes invalid shares. We empower the dishonest dealer and consider the case when he subliminally leaks information in valid shares, allowing an adversary to access the secret prior to the reconstruction phase. We define the concept of Dealer-Leakag...

Legal Counseling is carried out by providing clear, directed explanations, so that the meaning and purpose of authentic deed are easily understood parties. Sometimes people only provide explanations documents without knowing legal issues. Article 15 paragraph 2 letter e Act No. 2014 explains that, "in addition to authority as referred in (1), Notary also authorized to: counseling connection wit...