2005年に施行された個人情報保護法は，公文書の公開における個人情報の墨塗りを義務づけている．しかし公文書が電子文書として保管·運用され，さらに電子署名が付されている場合，署名生成後に墨塗りを施した文書は検証に失敗する．これは，通常の署名技術が文書に対する正当な変更（墨塗り）と不正な変更（改竄）を区別できないためである．このような問題を解決する手段として，いくつかの墨塗り署名方式が提案されている．しかし従来の墨塗り署名方式では，誰が墨塗りを施したかを特定することが困難であった．本稿は，墨塗り者の特定を可能とする新しい墨塗り署名方式（PIAT署名）を提案する．またいくつかの墨塗り署名方式の比較検討を行う．%When a document is disclosed with hiding privacy information, masking (sanitization) is widely used as a standard technology for paper documents. However, no corresponding technology has not been established for electronic documents. In addition, when digital signature schemes are combined in order to assure the integrity of disclosed information, the verification will be failed because standard digital signature schemes are not able to distinguish appropriate alternations (sanitizations) from inappropriate alternations (forgeries) in the sanitized document. The sanitizable signature scheme is a possible solution in which sanitizings of partial information are possible, after a signature is signed on the original (unsanitized) document. However, in previously proposed schemes, sanitizations by plural sanitizers were impossible, or even if it is possible, it was hard to identify who sanitized which subdocuments. This paper proposes a new sanitizable signature scheme "PIATS" in which plural sanitizations are possible and verifiers can identify sanitizers. Also some sanitizable signature schemes are compared and analyzed in this paper.
展开▼
