Internship Opening: Aggregate Signatures for Mutable Messages

Aggregate Signatures for Mutable Messages

Hardware and Fancy Cryptology
Hardware and Fancy Cryptology

Many protocols rely on generation, exchange and processing of mutable messages, i.e., they base their correct functioning on the recipient of a control message “trusting” that the originator of the message, as well as any intermediate systems that the message may have traversed from the originator to the recipient, have been “doing the right thing”: generating a mutable message with semantically correct content, and modifying the message in transit according to protocol rules. Often, however, protocols do not have explicit ways to ensure that this assumption is respected.

This is critical in particular (although not only) in routing protocols, both in link-state protocols (e.g. OLSR, OSPF) and distance-vector protocols (e.g. AODV, LOADng, RPL). In each of these protocols, it can be observed that information crucial to the protocol is completely unprotected against non-compliant implementations, deliberate (or even malicious) interference and manipulation. A desirable system with cryptographic enhancements, would allow the recipient of a message to verify and authenticate:

  • The originator and content of the original message ;
  • The chain of intermediate systems, through which the message has traveled ;
  • The “chain of modifications” made by intermediate systems to the original message (and to “audit” the modification chain).

If message sizes and computational resources were not an issue, then simply replicating and stacking messages and standard signatures could provide the necessary functionality. However, issues of battery consumption and congestion (transmitting multiple copies of the same message, with multiple signatures, or even a single message with multiple stacked signatures, one for each forwarder), as well as the increased risk of fragmentation of large packets (especially across links such as IEEE 802.15.4) in a lossy environment (in which loss of fragments is not rare) renders this impractical; more subtle approaches need thus to be explored.

Research Topics

Our research team is working on aspects of the use of aggregate signatures for advanced security mechanisms — for a number of different protocols and applications. The objective of this research internship is to contribute to these ongoing activities, which includes:

  • Investigate the use of aggregate signatures based on elliptic curve cryptography, permitting tractable mutable messages with highly compact signatures.
  • Investigate appropriate curves and cryptographic parameters for these advanced signature schemes applied to extensions of the protocols above (and others), taking into consideration space limits imposed by the protocols and the highly constrained power and computational resources available to many of the routing objects.
  • As feasible, develop and integrate a prototype solution into a relevant demonstrator.

Candidate Qualifications and Skills

  • The working language is English, thus a high level of English (written and oral) is required.
  • Programming in C/C++, Java, and general ease in programming is required.
  • The ability to work efficiently and autonomously, in a multi-cultural team, is required.
  • A strong background in networking and communications is appreciated.
  • Strong background in mathematics, in EC cryptography, and in MATLAB, is appreciated.

Period & Practicalities

More info

  • Routing Protocol Security