Daniel Krenn

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Efficient scalar multiplication in Abelian groups (which is an important operation in public key cryptography) can be performed using digital expansions. Apart from rational integer bases (double-and-add algorithm), imaginary quadratic integer bases are of interest for elliptic curve cryptography , because the Frobenius endomorphism fulfils a quadratic(More)
We consider digital expansions to the base of τ , where τ is an algebraic integer. For a w ≥ 2, the set of admissible digits consists of 0 and one representative of every residue class modulo τ w which is not divisible by τ. The resulting redundancy is avoided by imposing the width w-NAF condition, i.e., in an expansion every block of w consecutive digits(More)
For fixed t ≥ 2, we consider the class of representations of 1 as sum of unit fractions whose denominators are powers of t or equivalently the class of canonical compact t-ary Huffman codes or equivalently rooted t-ary plane " canonical " trees. We study the probabilistic behaviour of the height (limit distribution is shown to be normal), the number of(More)
We consider digital expansions in lattices with endomorphisms acting as base. We focus on the w-non-adjacent form (w-NAF), where each block of w consecutive digits contains at most one non-zero digit. We prove that for suciently large w and an expanding endomorphism, there is a suitable digit set such that each lattice element has an expansion as a w-NAF.(More)
We present an average case analysis of two variants of dual-pivot quicksort, one with a non-algorithmic comparison-optimal partitioning strategy, the other with a closely related algorithmic strategy. For both we calculate the expected number of comparisons exactly as well as asymptotically, in particular, we provide exact expressions for the linear,(More)
In a multi-base representation of an integer (in contrast to, for example, the binary or decimal representation) the base (or radix) is replaced by products of powers of single bases. The resulting numeral system is usually redundant, which means that each integer can have multiple different digit expansions. We provide a general asymptotic formula for the(More)