Abstract
Cryptographic commitments are either unconditionally hiding or unconditionally binding, but cannot be both. As a consequence, the security of commonly used commitment schemes is threatened in the long-term, when adversaries become computationally much more powerful. We improve over this situation by putting forward a new notion of commitment schemes, so called long-term commitment schemes. These schemes allow for long-term protection because they allow to adjust the protection level after the initial commitment. We also present a construction of a long-term commitment scheme. Unfortunately, it seems impossible to prove the security of such a scheme using the traditional commitment binding definition. Therefore, we put forward a new notion of binding commitments, so called extractable-binding commitments, and use this notion to establish a security proof for our proposed long-term commitment scheme.
This work has been co-funded by the DFG as part of project S6 within the CRC 1119 CROSSING.
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Buldas, A., Geihs, M., Buchmann, J. (2017). Long-Term Secure Commitments via Extractable-Binding Commitments. In: Pieprzyk, J., Suriadi, S. (eds) Information Security and Privacy. ACISP 2017. Lecture Notes in Computer Science(), vol 10342. Springer, Cham. https://doi.org/10.1007/978-3-319-60055-0_4
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