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TPM background section

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Trolli Schmittlauch 2018-09-06 13:51:13 +02:00
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@ -134,7 +134,12 @@ Earlier versions of the requirements mandated an option to disable Secure Boot o
\subsection{TPM}\label{sec:TPM}
\acp{TPM}
\acp{TPM} are dedicated hardware components offering a variety of security services to a system \cite{197213}: \\
\acp{TPM} provide \textbf{secure storage} inside the module to store sensitive data like cryptographic keys in such a way that it can't be leaked to or stolen from processes running on the main CPU. \\
These stored keys can be used to execute cryptographic operations on behalf of the system, without the keys getting transfered to the outside of the module. \\
The \textbf{attestation} functionality can attest the identity of software by calculating a hash sum of the supplied binary, signing it with its internal key to prove a certain system configuration or software version to third parties having a corresponding verification key. When pre-deployed with a unique key, all previously mentioned functionality can be combined to provide a \textbf{unique machine identity} and form a hardware trust anchor for running systems. \\
A \textbf{continuous trust chain} can be built from the boot-up on if all software components, starting from the firmware on, let the \ac{TPM} attest the processes to be launched and compare these attestations with the ones stored previously in the module's secure storage. A similar boot policy is \textit{authenticated booting}, where the \ac{TPM} calculates the checksum of each boot stage but doesn't enforce any signature checks but only stores the results inside its secure internal registers, from where the system status can be queried later on.\cite{hartigLateralThinkingTrustworthy2017} In contrast to UEFI Secure Boot \ref{sec:SecureBoot}, it is also possible to securely attest and launch code using special \textit{late-launch} CPU instructions introduced into AMD and Intel chipsets without providing a continuous trust chain from the firmware on \cite{hartigLateralThinkingTrustworthy2017}. \\
Additionally, \acp{TPM} provide important support functionality cryptographic algorithms like \textbf{secure counters}, a \textbf{secure clock} for peripherals and a \textbf{secure source of entropy}. \cite{197213}
lockdown techniques: TPM, secure boot