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This thesis deals with the analysis and design of trusted computing platforms. Trusted computing technology is a relatively new enabling technology to improve the trustworthiness of computing platforms. With minor changes to the boot process and the addition of a new hardware security component, called TPM (Trusted Platform Module), trusted computing platforms offer the possibility to verifiably report their integrity to external parties (i.e., remote attestation) and to bind information to a specific platform (i.e., sealed storage).
The first part of this thesis mainly focuses on the analysis of existing trusted computing platforms. We analyze the functionality provided by the specifications of the TCG (Trusted Computing Group) and purely software-based alternatives. Based on this analysis we present an improvement to a software-based attestation scheme: we propose to measure the execution time of a memory checksum function locally (with the time stamping functionality of the TPM) instead of remotely (over the network).
We also study the resilience of trusted computing platforms against hardware attacks. We describe how attacks on the communication interface of the TPM can circumvent the measured boot process. The feasibility of these attacks is investigated in practice. Additionally we explore which operations should be targeted with a side channel attack to extracts the secret keys of a TPM.
The second part of this thesis addresses some of the challenges to implement trusted computing technology on embedded and recon?gurable devices. One of the main problems when integrating a TPM into a system-on-chip design, is the lack of on-chip reprogrammable non volatile memory. We develop schemes to securely externalize the non-volatile storage of a TPM. One scheme relies a new security primitive, called a reconfigurable physical unclonable function, and another extends the security perimeter of the TPM to the external memory with a cryptographic prot[...]
The position is initially for two years, with possibility for extension upon successful progress in the PhD studies.
Recent public-key cryptography is largely based on number theory problems, such as factoring or computing of discrete logarithm. These systems constitute an excellent choice in many applications, and their security is well defined and understood. One of the major drawbacks, though, is that they will be vulnerable once quantum computers of an appropriate size are available. There is then a strong need for alternative systems that would resist attackers equipped with quantum technology.\r\n\r\n
One of the most well-known systems of this kind is the McEliece cryptosystem, introduced in 1978, that is based on algebraic coding theory. There are no known vulnerabilities against quantum computers, and it has a very fast and efficient encryption procedure. However, it has also one big flaw, the size of the public key, that makes it impractical for many applications.\r\n\r\n
The first part of this thesis is dedicated to finding a way to significantly reduce the size of the public key.\r\nLatest publications achieve very good results by using codes with particular structures, obtaining keys as small as 4,096 bits. Unfortunately, almost all of the variants presented until now have been broken or proven to be insecure against the so-called structural attacks, i.e. attacks that aim to exploit the hidden structure in order to recover the private key. \r\nMy work is based on Generalized Srivastava codes and represents a generalization of the Quasi-Dyadic scheme proposed by Misoczki and Barreto, with two advantages: a better flexibility, and improved resistance to all the known attacks. An efficient implementation of the above scheme is also provided, as a result of a joint work with P.-L. Cayrel and G. Hoffmann.\r\n\r\n
In the next chapters, other important aspects of code-based cryptography are investigated. These include the study of a higher security standard, called indistinguishability under a chosen ciphertext attack, in the standard model, and th[...]
We build on Barrington\'s theorem [JCSS \'89] and on the previous leakage-resistant constructions by Ishai et al. [Crypto \'03] and Faust et al. [Eurocrypt \'10]. Our construction exploits properties of A_u beyond what is sufficient for Barrington\'s theorem.