Jacob Löfvenberg

A class of traceability codes

Traceability codes are identifiable parent property (IPP) codes with the additional requirement that the Hamming distance can be used to trace a parent of a word. Traceability codes can be used for constructing digital fingerprints in order to deter users from illegally copying digital data. We construct a class of traceability codes and determine the exact parameters of some of the codes in this class.

Random codes for digital fingerprinting

Fingerprinting of digital documents are considered in the context of colluding pirates who want to create an untraceable copy. The performance of random fingerprinting in conjunction with a correlation-based testing method is presented, and complexity advantages of suboptimal tracing is discussed.

A power-efficient, low-complexity, memoryless coding scheme for buses with dominating inter-wire capacitances

In this paper we present a simplified model of parallel, on-chip buses, motivated by the movement toward CMOS technologies where the ratio between interwire capacitance and wire-to-ground capacitance is very large. We also introduce a ternary bus state representation, suitable for the bus model. Using this representation we propose a coding scheme without memory which reduces energy dissipation in the bus model by approximately 20-30% compared to an uncoded system. At the same time the proposed coding scheme is easy to realize, in terms of standard cells needed, compared to several previously proposed solutions.

Non-redundant coding for deep sub-micron address buses

A coding technique for deep submicron address buses with interwire capacitances dominating the wire-to-ground capacitances is presented. This code is similar to Gray codes, in the sense that it defines an ordering of the binary space, such that adjacent codewords dissipate little energy when sent consecutively. The ordering is shown to be close to optimal, as to the energy dissipation, when sending the whole sequence in order. A circuit diagram realizing the coder is presented, using only n-1 two-input gates, where n is the bus width. Simulations show an improvement in energy dissipation of more than 50% over an uncoded bus in several cases, depending on the data being coded.

Minimal redundancy, low power bus coding

A new approach to low redundancy coding for reducing power dissipation in parallel on-chip, deep sub-micron buses is presented. It is shown that the new approach allows lower power dissipation than previous solutions in the given model, yielding reductions of 24% to 41% compared to uncoded transmission for the considered bus widths. Finally some important open problems are given.

Binary Fingerprinting Codes

Three binary fingerprinting code classes with properties similar to codes with the identifiable parent property are proposed. In order to compare such codes a new combinatorial quality measure is introduced. In the case of two cooperating pirates the measure is derived for the proposed codes, upper and lower bounds are constructed and the results of computer searches for good codes in the sense of the quality measure are presented. Some properties of the quality measure are also derived.