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paper: extend future work and UI foo

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jaseg 2019-02-13 17:18:34 +09:00
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directions/research_directions.tex
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@ -598,6 +598,7 @@ $h$.
% FIXME find and consistently apply a nice name for this handshake method
\subsection{Alternative uses for interactive public channel binding}
\label{altuse}
The channel binding method described above can be used in any scenario where a secure channel between two systems must
be established where one party has a display of some sort and the other party has an input device of some sort.
@ -668,7 +669,6 @@ above, then copying the key through it. Compared to current common practice this
transfer a key by simply reading out aloud the channel binding fingerprint. This reduces the problem of a digital
out-of-band channel trusted for direct transfer of manipulation-sensitive key material to the problem of two users being
sure whether they're actually talking to each other instead of an impostor.
% FIXME
\section{Hardware implementation}
\subsection{Hardware overview}
@ -691,14 +691,42 @@ Additionally, those operations are only invoked infrequently any time the device
% separate power supplies, possible future filtering of power/gnd and comms link signals
\subsection{Usability considerations}
% buzzer, leds etc.
\paragraph{Security-relevant UI components}
In many systems such as common TLS-based systems, overall system security heavily depends on implementation details such
as certificate checking and user interface details such as the precise structure of security warning messages and how
they can be overridden. The complexity of these components in practice often leads to insecure systems, such as a system
using TLS checking a certificate's internal validity but omitting checks on the certificate's chain of trust. A nice
property of the key estabilishment sytsem outlined in this paper is that it is both very simple, reducing surface for
errors and it tightly couples the critical channel binding step during key establishment to the overall system's user
interface. In a system using either keyboard or mouse-based interactive channel binding, an implementation that does not
perform the channel binding step correctly would simply not work. If the host does not display the correct fingerprint
the user cannot enter it and the device will not complete the binding step. If the device does not relay fingerprint
data correctly during pairing the host application would clearly indicate to the user things are amiss with the input
not matching the fingerprint. Since the channel fingerprint is computed in a cryptographically well-defined way based
on entropy contributed by both partners during pairing a implementer would not even be able to accidentially degrade
fingerprint security.
The critical point from an UI perspective in this pairing scheme is that the host application must display correct
instructions to the user for them to complete pairing. In particular the host application must put emphasis on the user
actually checking whether the device raised an alarm before confirming pairing after fingerprint input. Even if it
didn't the user would notice the device not functioning, but an attacker might have gained unauthorized access in the
meantime. Likewise, the device needs a clearly understandable method of indicating pairing failure to the user. In
practice a loud buzzer and a few bright LEDs would likely suffice for this.
\section{Evaluation}
% FIXME
\section{Future work}
The aspects outlined in section \ref{altuse} provide potential future research directions. The adaption of the system to
mouse input might be an interesting target for a user experience study, particularly in comparison with a purely
keyboard-based system. The SSH key exchange method would be an interesting target for a general-use systems
administration tool. Though we have done some basic security arguments in this paper, a more rigurous formalization
might be interresting for future use of this technology. We have soundly argued about the user experience benefits of
our method, but we have not performed any field experiments to back up these arguments. Future research might analyze
the practical security a system as outlined in this paper yields under real-world conditions. The various trade-offs of
e.g. keyboard vs. mouse input, fingerprint lenght and design details of the pairing UI might be analyzed with respect to
practical usability and security.
\section{Conclusion}
% FIXME