{"publisher":"Springer","author":[{"last_name":"Abusalah","full_name":"Abusalah, Hamza M","id":"40297222-F248-11E8-B48F-1D18A9856A87","first_name":"Hamza M"},{"id":"46B4C3EE-F248-11E8-B48F-1D18A9856A87","full_name":"Fuchsbauer, Georg","first_name":"Georg","last_name":"Fuchsbauer"},{"last_name":"Pietrzak","first_name":"Krzysztof Z","id":"3E04A7AA-F248-11E8-B48F-1D18A9856A87","orcid":"0000-0002-9139-1654","full_name":"Pietrzak, Krzysztof Z"}],"file":[{"access_level":"open_access","checksum":"34fa9ce681da845a1ba945ba3dc57867","creator":"system","file_id":"5273","file_size":515000,"date_updated":"2020-07-14T12:44:39Z","relation":"main_file","file_name":"IST-2017-765-v1+1_838.pdf","date_created":"2018-12-12T10:17:20Z","content_type":"application/pdf"}],"related_material":{"record":[{"id":"83","status":"public","relation":"dissertation_contains"}]},"oa_version":"Submitted Version","month":"06","publication_status":"published","date_published":"2016-06-09T00:00:00Z","has_accepted_license":"1","status":"public","day":"09","_id":"1229","scopus_import":1,"date_created":"2018-12-11T11:50:50Z","ddc":["005","600"],"page":"285 - 303","language":[{"iso":"eng"}],"quality_controlled":"1","abstract":[{"lang":"eng","text":"Witness encryption (WE) was introduced by Garg et al. [GGSW13]. A WE scheme is defined for some NP language L and lets a sender encrypt messages relative to instances x. A ciphertext for x can be decrypted using w witnessing x ∈ L, but hides the message if x ∈ L. Garg et al. construct WE from multilinear maps and give another construction [GGH+13b] using indistinguishability obfuscation (iO) for circuits. Due to the reliance on such heavy tools, WE can cur- rently hardly be implemented on powerful hardware and will unlikely be realizable on constrained devices like smart cards any time soon. We construct a WE scheme where encryption is done by simply computing a Naor-Yung ciphertext (two CPA encryptions and a NIZK proof). To achieve this, our scheme has a setup phase, which outputs public parameters containing an obfuscated circuit (only required for decryption), two encryption keys and a common reference string (used for encryption). This setup need only be run once, and the parame- ters can be used for arbitrary many encryptions. Our scheme can also be turned into a functional WE scheme, where a message is encrypted w.r.t. a statement and a function f, and decryption with a witness w yields f (m, w). Our construction is inspired by the functional encryption scheme by Garg et al. and we prove (selective) security assuming iO and statistically simulation-sound NIZK. We give a construction of the latter in bilinear groups and combining it with ElGamal encryption, our ciphertexts are of size 1.3 kB at a 128-bit security level and can be computed on a smart card."}],"department":[{"_id":"KrPi"}],"file_date_updated":"2020-07-14T12:44:39Z","year":"2016","volume":9696,"user_id":"2DF688A6-F248-11E8-B48F-1D18A9856A87","oa":1,"ec_funded":1,"date_updated":"2023-09-07T12:30:22Z","publist_id":"6105","acknowledgement":"Research  supported  by  the  European  Research  Council,  ERC  starting  grant (259668-PSPC) and ERC consolidator grant (682815 - TOCNeT).","alternative_title":["LNCS"],"conference":{"start_date":"2016-06-19","location":"Guildford, UK","name":"ACNS: Applied Cryptography and Network Security","end_date":"2016-06-22"},"pubrep_id":"765","citation":{"mla":"Abusalah, Hamza M., et al. <i>Offline Witness Encryption</i>. Vol. 9696, Springer, 2016, pp. 285–303, doi:<a href=\"https://doi.org/10.1007/978-3-319-39555-5_16\">10.1007/978-3-319-39555-5_16</a>.","chicago":"Abusalah, Hamza M, Georg Fuchsbauer, and Krzysztof Z Pietrzak. “Offline Witness Encryption,” 9696:285–303. Springer, 2016. <a href=\"https://doi.org/10.1007/978-3-319-39555-5_16\">https://doi.org/10.1007/978-3-319-39555-5_16</a>.","ista":"Abusalah HM, Fuchsbauer G, Pietrzak KZ. 2016. Offline witness encryption. ACNS: Applied Cryptography and Network Security, LNCS, vol. 9696, 285–303.","short":"H.M. Abusalah, G. Fuchsbauer, K.Z. Pietrzak, in:, Springer, 2016, pp. 285–303.","apa":"Abusalah, H. M., Fuchsbauer, G., &#38; Pietrzak, K. Z. (2016). Offline witness encryption (Vol. 9696, pp. 285–303). Presented at the ACNS: Applied Cryptography and Network Security, Guildford, UK: Springer. <a href=\"https://doi.org/10.1007/978-3-319-39555-5_16\">https://doi.org/10.1007/978-3-319-39555-5_16</a>","ieee":"H. M. Abusalah, G. Fuchsbauer, and K. Z. Pietrzak, “Offline witness encryption,” presented at the ACNS: Applied Cryptography and Network Security, Guildford, UK, 2016, vol. 9696, pp. 285–303.","ama":"Abusalah HM, Fuchsbauer G, Pietrzak KZ. Offline witness encryption. In: Vol 9696. Springer; 2016:285-303. doi:<a href=\"https://doi.org/10.1007/978-3-319-39555-5_16\">10.1007/978-3-319-39555-5_16</a>"},"doi":"10.1007/978-3-319-39555-5_16","intvolume":"      9696","title":"Offline witness encryption","type":"conference","project":[{"grant_number":"259668","_id":"258C570E-B435-11E9-9278-68D0E5697425","name":"Provable Security for Physical Cryptography","call_identifier":"FP7"},{"_id":"258AA5B2-B435-11E9-9278-68D0E5697425","grant_number":"682815","name":"Teaching Old Crypto New Tricks","call_identifier":"H2020"}]}