Letter to the Editor

In 2001, the number of individuals who took the tests of General Educational Development (GED) topped one million for the first time in history. Each year since 1980, between 400,000 and 500,000 individuals have passed the exams and received their GED credential. GED certificates constituted 25% of the total of regular high school diplomas plus GED certificates issued in 2001. When this figure ...

With this construction we show that MD5 collisions can be crafted easily in such a way that the principles underlying the trust in Public Key Infrastructure are violated. In particular we find it worrying that from one certificate alone it cannot be determined whether another, different certificate may exist with the same signature. For the second certificate the issuing Certification Authority...

An isomorphism certificate of a labeled tournament T is a labeled subdigraph of T which together with an unlabeled copy of T allows the errorless reconstruction of T . It is shown that any tournament on n vertices contains an isomorphism certificate with at most n log2 n edges. This answers a question of Fishburn, Kim and Tetali. A score certificate of T is a labeled subdigraph of T which toget...

We study certificates in static data structures. In the cell-probe model, certificates are the cell probes which can uniquely identify the answer to the query. As a natural notion of nondeterministic cell probes, lower bounds for certificates in data structures immediately imply deterministic cell-probe lower bounds. In spite of this extra power brought by nondeterminism, we prove that two wide...

Certificates play an essential role in public-key cryptography, and are likely to become a cornerstone of commerce-related applications. Traditional certificates, however, are not secure against certificate lending, i.e., a situation in which a certificate holder voluntarily shares with others the rights bestowed upon him through a certificate. This type of abuse is a concern in several types o...

Consider a world where exporting proof evidence into a well defined, universal, and permanent format is taken as “feature zero” for computational logic systems. In such a world, provers will communicate and share theorems and proofs; libraries will archive and organize proofs; and marketplaces of proofs would be open to any prover that admits checkable proof objects. In that world, proof checke...

Modular and local reasoning about object-oriented programs has been widely studied for programing languages such as C# and Java. Once source programs have been proven, the next verification challenge is to ensure that the code produced by the compiler is correct. Since verifying a compiler can be extremely complex, this paper uses proof-transforming compilation, an alternative approach which au...