FUNCTIONAL ANALYSIS

The input and output states of a chip can be monitored using an oscilloscope, or special purpose probes such as logic state analysers or protocol analysers, to acquire a picture of the behaviour of the chip over time or in response to input signals.

Many patented goods are not sold with restrictive licences, and hence a bona fide purchaser cannot usually be prevented by the patent from doing what they like with the patented product. Indeed, the patent itself may give the reverse engineer valuable information on how the patented product operates.

However, a competitive product produced by reverse engineering may still infringe the patent itself - patent infringement does not require copying, and so "clean-room" techniques do not assist.

Backward and Forward

Most of the machines we encounter in everyday life are one-way devices. Kitchen appliances turn bread into toast and cabbage into cole slaw, but they cannot perform the opposite transformations. Even machines that claim to be reversible adopt a very shallow notion of what it means to go backwards. The drill in my tool box has settings marked "forward" and "reverse," but no matter which I choose, I cannot undrill a hole. Thegearshift in my car also has a position labeled R, but when I back up, the engine keeps turning in the same direction; if the car were truly reversed, it would suck in pollution through the tailpipe, converting it into gasoline and air.

HARDWARE REVERSE ENGINEERING TECHNIQUES

PRINTED CIRCUIT BOARDS (PCBS)

Computer vision has been widely used to scan PCBs for quality control and inspection purposes, and based on this, there are a number of machine vision for analysing and reverse engineering PCBs (3). Several firms on the Internet offer a service of scanning a PCB and supplying a corresponding netlist.

INTEGRATED CIRCUIT (IC) COMPONENTS

This is much harder work, since everything is on a much smaller scale.

The first step is to get through the encapsulating material into the product itself, by chemical etching or grinding. This can be tough in itself, since some manufacturers include hard particles such as carborundum or sapphire in the encapsulating the resin, so that mechanical grinding also destroys the chip.

Once at the chip surface, each layer of components is photographed, then ground away to reveal the layer below. This process reveals the structure of the chip. Again, the process can be made more difficult, for example by providing some of the components vertically across several layers.

HARDWARE REVERSE ENGINEERING

Techniques now exist for visually scanning mechanical parts and generating CAD models from them, using machine vision technology; for example, the REFAB (Reverse Engineering - Feature Based) tool available from the Department of Computer Science of the University of Utah (2) and ARL's site. In REFAB, a laser digitiser is used to the scan the part, and the analysis software then analyses the shape of the part, using features which are based on typical machining operations, to generate a computerised manufacturing description which can be displayed, used to copy the product, or produce new products using the design.

REVERSE ENGINEERING

Reverse engineering, as the name implies, is the reverse of this; in other words, the attempt to recapture the top level specification by analysing the product - "attempt" because it is not possible in practice, or even in theory, to recover everything in the original specification purely by studying the product.

Reverse engineering is difficult and time consuming, but it is getting easier all the time thanks to IT, for two reasons:

• Firstly, as engineering techniques themselves become more computerised, more of the design is due to the computer. Thus, recognisable blocks of code, or groups of circuit elements on a substrate, often occur in many different designs produced by the same computer program. These are easier to recognise and interpret than a customised product would be.
• Secondly, artificial intelligence techniques for pattern recognition, and for parsing and interpretation, have advanced to the point where these and other structures within a product can be recognised automatically.

Development of FFBD

FFBDs can be developed in a series of levels. FFBDs show the same tasks identified through functional decomposition and display them in their logical, sequential relationship. For example, the entire flight mission of a spacecraft can be defined in a top level FFBD, as shown in Figure 2. Each block in the first level diagram can then be expanded to a series of functions, as shown in the second level diagram for "perform mission operations." Note that the diagram shows both input (transfer to operational orbit) and output (transfer to space transportation system orbit), thus initiating the interface identification and control process. Each block in the second level diagram can be progressively developed into a series of functions, as shown in the third level diagram on Figure 2.^[6]

These diagrams are used both to develop requirements and to identify profitable trade studies. For example, does the spacecraft antenna acquire the tracking and data relay satellite (TDRS) only when the payload data are to be transmitted, or does it track TDRS continually to allow for the reception of emergency commands or transmission of emergency data? The FFBD also incorporates alternate and contingency operations, which improve the probability of mission success. The flow diagram provides an understanding of total operation of the system, serves as a basis for development of operational and contingency procedures, and pinpoints areas where changes in operational procedures could simplify the overall system operation. In certain cases, alternate FFBDs may be used to represent various means of satisfying a particular function until data are acquired, which permits selection among the alternatives.^[6]

Functional Flow Block Diagram

A Functional Flow Block Diagram (FFBD) is a multi-tier, time-sequenced, step-by-step flow diagram of a system’s functional flow.^[2]

The FFBD notation was developed in the 1950s, and is widely used in classical systems engineering. FFBDs are one of the classic business process modeling methodologies, along with flow charts, data flow diagrams, control flow diagrams, Gantt charts, PERT diagrams, and IDEF.^[3]

FFBDs are also referred to as Functional Flow Diagrams, functional block diagrams, and functional flows.^[4]