Cryptography and Security

Cryptography is the science that provides technical solutions to ensure that a message, sent or stored, has the following properties:

• Confidentiality: the message is not intelligible to whoever is not authorized to read it
• Integrity: the message is not modified without the author’s consent
• Authenticity: the origin of the message can be traced back to a specific author

The tools developed by cryptography are cryptographic primitives and cryptographic protocols, and their soundness is first evaluated from a theoretical standpoint through public scrutiny. A crucial requirement for such tools is that their security cannot hinge on the lack of knowledge about their structure, but instead should rely only on the lack of knowledge of a single unknown parameter, the encryption key. Following the evaluation for theoretical soundness, the primitives and protocols must be practically realized, and employed in the proper contexts. Such a task requires that the realizations are efficient, effective in providing the desired properties, and do not reveal the encryption key as a side effect of the realization of the algorithm. Such concerns are typical of the applied cryptography research on which the security group focuses on. In particular, the security group focuses on the following areas of research:

• Efficient software and hardware implementation: Providing highly efficient implementations is crucial in devices working with limited energy supply and that are, therefore, tightly constrained by the available energy pool (e.g. mobile phones, small sensors, embedded medical devices). The interests of the security group focus on exploiting architectural features avaliable on mobile and low power devices to provide effective and efficient implementations. In particular, the group is currently tackling techniques for efficient realizations of innovative cryptosystems, such as quantum-computer resistant cryptographic primitives and lightweight symmetric ciphers for constrained devices.
• Side channel attacks and countermeasures: A quite effective way to extract the secret encryption key from a physical cipher implementation is to observe one or more side-effects of the computation itself (e.g. the time required to compute a certain primitive, the energy consumed in doing so). This approach to the extraction of the secret key is known as a side channel attack, and is able to breach standard abiding and functionally correct implementations regardless of the mathematical security of the implemented primitive. With respect to these attacks, the group designed automated compiler-based securization techniques to detect vulnerabilities and protect cryptographic primitives against side channel attacks. The implementation of such analysis and automated protection was realized within the popular LLVM compiler framework.
• Cryptography in emerging application domains: Cyber-physical security: the group designed a key agreement protocol and an overlay encryption protocol for the KNX standard, which is used for building automation in households, hotels, hospitals. The designed protocol enciphers and authenticates the data sent without modifying the datagram headers, allowing a drop-in deployment of the protected devices.
• Data security and privacy: The group tackled the security and privacy of large amount of encrypted outsourced data when dealing with an honest-but-curious storage provider. They also designed an efficient solution to protect the access pattern to remotely stored data, with in-house equivalent privacy guarantees.
• Social network privacy and security: The overall aim of the research has been to shift the handling of security-related aspects onto the client. In particular, the group designed a social network platform where the client handles the encryption and decryption of the messages, and is the only one in knowledge of the encryption keys, an approach known as end-to-end encryption. The group is currently working on the design of an asynchronous messaging protocol providing private acquaintances discovery with respect to the service provider.
• Secure e-mail communication and data authentication: The group reviewed the security of the well-established GPG secure e-mail and data authentication protocol highlighting unnoticed weaknesses and proposing mitigations.