## 2 Decision Making
### A Vulnerability in the Process  
To give a concrete example of the vulnerabilities that are the subject of this paper, the details of the different kinds of decision making processes are not relevant. Rational processes, either devoid of political significance or fully influenced by the affective biases that these introduce, share a very basic and common ground: they start from a set of possible choices and proceed to pick one (or more) of them as the result. We deem useful to model the key aspects of the process in a very simplified fashion as follows. We define two sets:  
* The initial set (\(IS\)) is the input of the process: the set of options initially available to the decision maker. * The chosen set (\(CS\)) is the output of the process: the set of options representing what the decision maker has decided. It could be a stand choice or a set of choices. The relationship in between \(IS\) and \(CS\) is the following one:  
\[CS\leq IS\]  
This relationship is always true in a correctly modeled scenario, since the goal of a decision making process is reducing the \(IS\). Starting with a \(IS\) of cardinality greater than one, the two limit conditions where the outcome is either  
\[IS\equiv CS\]  
or  
\[CS\equiv\emptyset\]  
represent a failure of the process. In both scenarios the decision maker cannot reach a decision. The former scenario leaves the decision maker with the same set of choices present in the initial set. The process failed by being unable to reduce uncertainty between the available options, consequently not allowing to highlight the most desirable ones. The latter scenario represents a situation in which the decision maker is left with no viable options. Since some viable options, by definition, were present in the initial set, the process failed by ruling them all out, for example by applying exceedingly restrictive constraints. Let us illustrate with an example how a malicious attacker can influence the decision making process to cause its failure, with a simple example that is not tied to any specific technology. A man survives a flight crash and finds himself stranded on a uninhabited island. He needs to eat, and for that reason he needs to choose between hunting, fishing and collecting vegetables. A simple decision process can proceed by sequentially applying constraints that allow to prune the choice tree. Hard constraints are applied early: our subject is unable to build a fishing rod because he has no idea of how to realize the fishing hook, so fishing is ruled out. Personal preference and rational considerations follow: he does not like vegetables, and he knows that they do not provide enough calories to survive. Only hunting is left as an option, but our unlucky (and quite picky) man discovers he does not bear the sight of blood. He ends up with no choice. The decision process failed, and missed the goal of indicating a way to satisfy the man's need for food. Could this failure be the outcome of a malicious attempt at thwarting the process? The answer is clearly positive. An attacker might have added a spurious constraint such as: \"vegetables do not provide enough calories for survival\", that reinforce the decision maker's natural inclination against the vegetable-gathering option and cause him to exclude it. An attacker might have removed other suitable options from \(IS\), like \"fishing with a net\" as a sub-alternative to \"fishing with rod and hook\". In these examples the attacker aims at driving the decision process towards the failure mode represented by \(CS\equiv 0\). A subtler way the attacker could trick the decision maker into failure is by injecting unrealistic but favorable options into the \(IS\) such as: \"you need to decide between hunting, fishing, collecting vegetables and going to the grocery store\". Of course the decision making process will pursue the maximum benefit with the minimum associated inconvenience, and consequently even slightly more favorable and/or less constrained options have good chances to be selected.