PIATS: A Partially Sanitizable Signature Scheme

In e-government or e-tax payment systems, appropriate alterations on digitally signed documents are required to hide personal information, namely privacy. Standard digital signature schemes do not allow such alternations on the signed documents since there is no means to distinguish appropriate alternations from inappropriate forgeries. The sanitizable signature scheme is a possible solution for such systems in which sanitizings of partial information are possible, after a signature is signed on the original (unsanitized) document. However, in previously proposed schemes, since sanitizers are anonymous, verifiers cannot identify sanitizers, and thus dishonest sanitizings are possible. This paper proposes a new sanitizable signature scheme “PIATS” in which partial information can be sanitized. Moreover, verifiers can identify sanitizers and thus dishonest sanitizings are eliminated.