{"id":2433,"date":"2018-03-05T12:24:22","date_gmt":"2018-03-05T12:24:22","guid":{"rendered":"https:\/\/prismacloud.eu\/?p=2433"},"modified":"2018-09-10T11:46:20","modified_gmt":"2018-09-10T11:46:20","slug":"chameleon-hashes-with-dual-long-term-trapdoors-and-their-applications","status":"publish","type":"post","link":"https:\/\/prismacloud.eu\/chameleon-hashes-with-dual-long-term-trapdoors-and-their-applications\/","title":{"rendered":"Chameleon-Hashes with Dual Long-Term Trapdoors and Their Applications"},"content":{"rendered":"<p style=\"text-align: justify;\"><strong>Title<\/strong><\/p>\n<p style=\"text-align: justify;\">Chameleon-Hashes with Dual Long-Term Trapdoors and Their Applications<\/p>\n<p style=\"text-align: justify;\"><strong>Authors<\/strong><\/p>\n<p style=\"text-align: justify;\">Stephan Krenn, Henrich C. P\u00f6hls, Kai Samelin and Daniel Slamanig<\/p>\n<p style=\"text-align: justify;\"><strong>Abstract\u00a0<\/strong><\/p>\n<p style=\"text-align: justify;\">A chameleon-hash behaves likes a standard collision-resistant hash function for outsiders. If, however, a trapdoor is known, arbitrary collisions can be found. Chameleon-hashes with ephemeral trapdoors (CHET; Camenisch et al., PKC 17) allow prohibiting that the holder of the long-term trapdoor can find collisions by introducing a second, ephemeral, trapdoor. However, this ephemeral trapdoor is required to be chosen freshly for each hash. We extend these ideas and introduce the notion of chameleon-hashes with dual long-term trapdoors (CHDLTT). Here, the second trapdoor is not chosen freshly for each new hash; Rather, the hashing party can decide if it wants to generate a fresh second trapdoor or use an existing one. This primitive generalizes CHETs, extends their applicability and enables some appealing new use-cases, including three-party sanitizable signatures, group-level selectively revocable signatures and break-the-glass signatures. We present two provably secure constructions and an implementation which demonstrates that this extended primitive is efficient enough for use in practice.<\/p>\n<p style=\"text-align: justify;\"><strong>Venue<\/strong><\/p>\n<p style=\"text-align: justify;\">1Oth International Conference on Cryptology, AFRICACRYPT 2018<\/p>\n<p style=\"text-align: justify;\"><strong>Place and Date<\/strong><\/p>\n<p style=\"text-align: justify;\">Marrakesh, Morocco,\u00a0May 7-9, 2018.<\/p>\n<p>[<a href=\"https:\/\/prismacloud.eu\/wp-content\/uploads\/2018\/09\/Chameleon-Hashes-with-Dual-Long-Term-Trapdoors-and-Their-Applications.pdf\">Download<\/a>]<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>A chameleon-hash behaves likes a standard collision-resistant hash function for outsiders. If, however, a trapdoor is known, arbitrary collisions can be found. Chameleon-hashes with ephemeral trapdoors (CHET; Camenisch et al., PKC 17) allow prohibiting that the holder of the long-term trapdoor can find collisions by introducing a second, ephemeral, trapdoor. However, this ephemeral trapdoor is required to be chosen freshly for each hash. We extend these ideas and introduce the notion of chameleon-hashes with dual long-term trapdoors (CHDLTT). Here, the second trapdoor is not chosen freshly for each new hash; Rather, the hashing party can decide if it wants to generate a fresh second trapdoor or use an existing one. This primitive generalizes CHETs, extends their applicability and enables some appealing new use-cases, including three-party sanitizable signatures, group-level selectively revocable signatures and break-the-glass signatures. We present two provably secure constructions and an implementation which demonstrates that this extended primitive is efficient enough for use in practice.<\/p>\n","protected":false},"author":2,"featured_media":1575,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7,8],"tags":[],"_links":{"self":[{"href":"https:\/\/prismacloud.eu\/wp-json\/wp\/v2\/posts\/2433"}],"collection":[{"href":"https:\/\/prismacloud.eu\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/prismacloud.eu\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/prismacloud.eu\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/prismacloud.eu\/wp-json\/wp\/v2\/comments?post=2433"}],"version-history":[{"count":10,"href":"https:\/\/prismacloud.eu\/wp-json\/wp\/v2\/posts\/2433\/revisions"}],"predecessor-version":[{"id":3177,"href":"https:\/\/prismacloud.eu\/wp-json\/wp\/v2\/posts\/2433\/revisions\/3177"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/prismacloud.eu\/wp-json\/wp\/v2\/media\/1575"}],"wp:attachment":[{"href":"https:\/\/prismacloud.eu\/wp-json\/wp\/v2\/media?parent=2433"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/prismacloud.eu\/wp-json\/wp\/v2\/categories?post=2433"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/prismacloud.eu\/wp-json\/wp\/v2\/tags?post=2433"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}