Alain P. Hiltgen

Secure Internet banking authentication

This article classifies common Internet banking authentication methods regarding potential threats and their level of security against common credential stealing and channel breaking attacks, respectively. The authors present two challenge/response Internet banking authentication solutions, one based on short-time passwords and one certificate-based, and relate them to the taxonomy above. There further outline how these solutions can be easily extended for nonrepudiation (that is, transaction signing), should more sophisticated content manipulation attacks become a real problem. Finally, they summarize their view on future requirements for secure Internet banking authentication and conclude by referencing real-live implementations

Password Interception in a SSL/TLS Channel

Simple password authentication is often used e.g. from an email software application to a remote IMAP server. This is frequently done in a protected peer-to-peer tunnel, e.g. by SSL/TLS.

Single-track Gray codes

A common use of Gray codes is in reducing quantisation errors in various types of analogue-to-digital conversion systems. As a typical example, a length n Gray code can be used to record the absolute angular positions of a rotating wheel by encoding the codewords on n concentrically arranged tracks. A number of reading heads, n, mounted radially across the trades, suffice to recover the codewords and it is well known that quantisation errors are minimised by using a Gray encoding. When a high resolution is required, the need for a large number of concentric tracks results in encoders with large physical dimensions. This poses a problem in the design of small-scale or high-speed devices. We propose single-trade Gray codes as a way of overcoming this problem. Let W/sub 0/,W/sub 1/...,W/sub p-1/ be the codewords of a Gray code C and write W/sub i/=[w/sub i//sup 0/,w/sub i//sup 1/,...,w/sub i//sup n-1/]/sup T/. We call the sequence w/sub 0//sup j/,w/sub 1//sup j/,...,w/sub p-1//sup j/ component sequence j of C.

Single-track circuit codes

Single-track circuit codes (STTCs) are circuit codes with codewords of length n such that all the n tracks which correspond to the n distinct coordinates of the codewords are cyclic shifts of the first track. These codes simultaneously generalize single-track Gray codes and ordinary circuit codes. They are useful in angular quantization applications in which error detecting and/or correcting capabilities are needed. A parameter k, called the spread of the code, measures the strength of this error control capability. We consider the existence of STCCs for small lengths n/spl les/17 and spreads k/spl les/6, constructing some optimal and many good examples. We then give a general construction method for STCCs which makes use of ordinary circuit codes. We use this construction to construct examples of codes with 360 and 1000 codewords which are of practical importance. We also use the construction to prove a general result on the existence of STCCs for general spreads.

Towards a better understanding of one-wayness: Facing linear permutations

The one-wayness of linear permutations, i.e., invertible linear Boolean functions F: {0,1}n → {0, 1}n, is investigated. For linear permutations with a triangular matrix description (tlinear permutations), we prove that one-wayness, C(F−1)/C(F), is non-trivially upperbounded by 16√n, where C(.) denotes unrestricted circuit complexity. We also prove that this upper bound strengthens as the complexity of the inverse function increases, limiting the one-wayness of t-linear permutations with C(F−1) = n2/(c log2(n)) to a constant, i.e., a value that is independent of n. Direct implications for linear and also non-linear permutations are discussed. Moreover, and for the first time ever, a description is given about where, in the case of linear permutations, practical one-wayness would have to come from, if it exists.