Type Flaw Attacks Research Articles

Approach to Detecting Type-Flaw Attacks Based on Extended Strand Spaces

Approach to Detecting Type-Flaw Attacks Based on Extended Strand Spaces

Detecting and preventing type flaws at static time*

A type flaw attack on a security protocol is an attack where an honest principal is cheated on interpreting a field in a message as the one with a type other than the intended one. In this paper, we shall present an extension of the LYSA calculus to cope with types, by using tags to represent the i ntended types of terms. We develop a Control Flow Analysis for this calculus which soundly over-approximates all the possible behaviour of a protocol and, in particular, is able to capture any type confusion that may occur during the protocol execution. The analysis acts in a descriptive way: it describes which violations may occur. In the same setting, our approach also offers a prescriptive usage: we can impose a type discipline, by forcing some data to be of the expected types. At this point, the analysis may statically check that type violations are not possible any longer. In other words, we instrument the code with the only checks necessary to enforce type security. Finally, we apply our framework to a multi-protocol setting, where the risk of having type flaw attacks is higher. Our analysis has been implemented and successfully applied to a number of security protocols, showing it is able to capture type flaw attacks. The implementation complexity of the analysis is low polynomial.

Chosen-name Attacks: An Overlooked Class of Type-flaw Attacks

In the context of Dolev-Yao style analysis of security protocols, we consider the capability of an intruder to dynamically choose and assign names to agents. This capability has been overlooked in all significant protocol verification frameworks based on formal methods. We identify and classify new type-flaw attacks arising from this capability.Several examples of protocols that are vulnerable to this type of attack are given, including Lowe's modification of KSL. The consequences for automatic verification tools are discussed.

Detecting and Preventing Type flaws: a Control Flow Analysis with Tags

A type flaw attack on a security protocol is an attack where an honest principal is cheated on interpreting a field in a message as the one with a type other than the intended one. In this paper, we shall present an extension of the LySa calculus with tags attached to each field, indicating the intended types. We developed a control flow analysis for analysing the extended LySa, which over-approximates all the possible behaviour of a protocol and hence is able to capture any type confusion that may happen during the protocol execution. The control flow analysis has been applied to a number of security protocols, either subject to type flaw attacks or not. The results show that it is able to capture type flaw attacks on those security protocols.

On preventing type flaw attacks on security protocols with a simplified tagging scheme

A type flaw attack on a security protocol is an attack in which a field in a message that was originally intended to have one type is subsequently interpreted as having another type. Heather et al. proved that type flaw attacks can be prevented by tagging each field with the information that indicates its intended type. We simplify Heather et al.'s tagging scheme by combining all the tags inside each encrypted component into a single tag and by omitting the tags on the outermost level. The simplification process reduces the sizes of messages in the security protocol. We also formally prove that our simplified tagging scheme is as secure as Heather et al.' with the strand space method.

How to prevent type flaw attacks on security protocols

A type flaw attack on a security protocol is an attack where a field that was originally intended to have one type is subsequently interpreted as having another type. A number of type flaw attacks have appeared in the academic literature. In this paper we prove that type flaw attacks can be prevented using a simple technique of tagging each field with some information indicating its intended type.