University of Paris-Sud 11
Sanitizable signature schemes allow for altering signed data in a signer-controlled way by a semi-trusted third party. This is contrary to standard digital signature schemes, which do not permit any modifications by any party without invalidating the signature. Due to transparency, a strong privacy notion, outsiders cannot see if the signature for a message was created by the signer or by the semi-trusted party. Accountability allows the signer to prove to outsiders if a message was original or touched by the semi-trusted party. Currently, block-level accountability requires to drop transparency. The authors allow for accountability for sanitizable signatures with transparency on the block-level.