\chapter{Introduction}
We all live in a world full of digital systems.
They appear as PCs, notebooks, cellular phones or embedded devices.
Especially the footprint of embedded computers became so small that they can be used in almost all elctrical devices.
This product category form the so called \emph{smart} devices.

With all these new devices a lot of societal problems could be solved in the past few decades.
Many of them automate services to the public like managing the bank account, public transportation or health services.
The list of digital service is endless and will still grow in the next decades.

The downside of all these digital services is that using these services generate a lot of data.
Besides of the intended exchange of information, many of the services try to extract metadata as well.
Metadata answers some of the following questions.
Which IP is connected? 
What kind of device is that? 
Is the software of the device up to date? 
Was this device here in the past?
What else did the owner on the device?
This list of questions can be continued arbitrarily.
Reselling the metadata brings the product manufacturer more margin on the product and hence more profit.
Consequently the market for metadata is growing with the Internet itself.
The result is a loss of trust in all kind of connected devices and software.
A User cannot know what is happening on a device she is using.

The Institute for Networks and Security therefore introduced the project DigiDow.
It introduces a digital authentication system, which minimizes the generation of metadata and hence preserves privacy for all users of the system.

\section{Project DigiDow}
The Project \emph{Digital Shadow} is under ongoing development at the Institute of Networks and Security and creates a scalable system for authentication.
Key feature is privacy by design and a provable system to create trust to the end user.

At this early stage the interfaces and interaction points are not fully defined.

This is a brief description of the process of authentication:
%TODO paste image here and describe it

\section{Biometric Sensor use case in DigiDow}
derive the use case of the Biometric sensor out of the above model.
%TODO description of BS in DigiDow

\section{Goals and Definitions}
You should be able to attach a variety of sensors to the system. 
The system should then fulfill the following requirements
\begin{itemize}
	\item \emph{Sensor Monitoring.} The System should be able to monitor the sensor itself.
	\item \emph{System Monitoring.} It should be possible to track the state of the system. Especially every modification of the system should be detected.
	\item \emph{Freshness of Sensor Data.} To prevent replay attacks, the system should proof that the provided biometric data is captured live.
	\item \emph{Integrity of Sensor Data.} As it is possible for an adversary to modify the provided data during the capturing process, integrity should guarantee that the data originates from the BS.
	\item \emph{Confidentiality of Sensor Data.} It should not be possible to eavesdrop any sensitive data out of the system. 
	Furthermore almost all kinds of metadata (e.\,g. information about the system or network information) should not be published
	\item \emph{Anonymity.} Given a message from a BS, an adversary should not be able to detect which BS created it
	\item \emph{Unforgeability.} Only honest BS should be able to be part of the DigiDow network. Corrupt systems should not be able to send valid messages.
\end{itemize}

Usage Model of Biometric Sensor

This thesis will describe a system, which is part of the Digital Shadow network.
Therefore it has to meet the common principles in information security, namely:
\begin{itemize}
	\item \emph{Availability}: 
	\item \emph{Integrity}: ISO 27000 (Data Integrity)
	\item \emph{Confidentiality}: ISO 27000
\end{itemize}

Upon AIC it should be possible for users to prove honesty of the system.
This is what \emph{trust} defines in information security

\subsection{Requirements}
\begin{itemize}
	\item given a set of software, this system should provide information that exactly this version of software is running on the system. (Integrity)
	\item The system must furthermore show that it is a member of valid biometric sensors (Attestation)
	\item All the given information should be anonymized. It should not be possible to gain any other information about the system (Anonymity)
	\item It should be ensured that no sensitive data is stored at the biometric sensor
\end{itemize}
Scope of this thesis is on implementing the system from from hardware to application layer.
Is is not supposed to think about the network communication.

\section{Description of structure}
\begin{enumerate}
	\item What exists out there?
	\item What is the theoretical solution
	\item What about the implementations used - what is the limitation of the used tools?
	\item How far are we? what has to be considered next?
\end{enumerate}

\chapter{Related Work}
There exist already many interesting projects and implementations which touch the field of trusted computing.
We will introduce some of these projects and discuss why these do not meet the purpose of this thesis.

Schear el.\,al.\@ developed a full featured trusted computing environment for cloud computing.
They show in their paper how a TPM of a hypervisor can be virtualized and used by the guest operating system.
This includes trusted bootstrapping, integrity monitoring, virtualization, compatibility with existing tools for fleet management and scalability\cite{keylime16}.
The concept of a well known virtual environment does, however, not apply to our contribution.
Furthermore, the the system should be self contained as good as possible and it should be possible to get information about the system via anonymous attestation.
%TODO what about the integrity measurements of keylime?

\begin{itemize}
	\item What exists in the field?
	\item Keylime - DONE
	\item Xaptum ECDAA
	\item FIDO 2 ECDAA
	\item Strongswan Attestation
	\item Linux IMA
	\item Secure Boot
	\item Intel TXT
	\item Trusted Execution Environment (TEE)
	\item nanovm (\url{nanovms.com})
	
\end{itemize}