Block-level Accountability for Transparent Sanitizable Signatures

The paradigm of treating security properties on the blocklevel in sanitizable signature schemes was introduced by Brzuska et al. at EuroPKI ’12. In this paper we extend their work in two respects: First, we provide a new construction which retains transparency, a stronger privacy property. In particular, we formalize the property of block-level accountability for sanitizable signatures with transparency. The original work by Brzuska et al. did not allow for transparency. We derive a provably secure construction, achieving the new notion. Second, a modification of our construction sacrifices transparency, but efficiently achieve Brzuska et al.’s stronger accountability notion also on the level of blocks. Our modified construction only requires a constant amount of signature generations to achieve block-level non-interactive public accountability property, which is a significant improvement over Brzuska et al.’s construction from EuroPKI ’12. We have implemented our constructions and the scheme introduced by Brzuska et al. at PKC ’09 to provide a detailed performance analysis.