eprintid: 10153741 rev_number: 9 eprint_status: archive userid: 699 dir: disk0/10/15/37/41 datestamp: 2023-02-28 16:29:51 lastmod: 2023-02-28 16:37:06 status_changed: 2023-02-28 16:29:51 type: report metadata_visibility: show sword_depositor: 699 creators_name: Abadi, Aydin creators_name: Murdoch, steven creators_name: Zacharias, Thomas title: Recurring Contingent Payment for Proofs of Retrievability ispublished: pub divisions: C05 divisions: F48 divisions: B04 divisions: UCL keywords: Cryptographic protocol, blockchain, smart contracts, fair exchange note: This work is licensed under an Attribution 4.0 International License (CC BY 4.0). abstract: Fair exchange protocols let two mutually distrusted parties exchange digital data in a way that neither can cheat. At CCS 2017, Campanelli et al. proposed two blockchain-based protocols for the fair exchange of digital coins and a certain service, i.e., “proofs of retrievability” (PoR), that take place between a buyer and seller. In this work, we identify two serious issues of these schemes; namely, (1) a malicious client can waste the seller’s resources, and (2) real-time leakage of information to non-participants in the exchange. To rectify the issues, we propose a “recurring contingent PoR payment” (RC-PoR-P). It lets the fair exchange reoccur while ensuring that the seller’s resources are not wasted, and the parties’ privacy is preserved. We implemented the RC- PoR-P. Our cost analysis indicates that the RC-PoR-P is efficient. The RC-PoR-P is the first of its kind that offers all the above features. date: 2021-09-10 date_type: published publisher: Cryptology ePrint Archive official_url: https://eprint.iacr.org/2021/1145 oa_status: green full_text_type: pub language: eng primo: open primo_central: open_green verified: verified_manual elements_id: 1970127 confidential: false lyricists_name: Abadi, Aydin lyricists_id: AKHEI13 actors_name: Abadi, Aydin actors_id: AKHEI13 actors_role: owner full_text_status: public series: Paper 2021/1145 pages: 50 citation: Abadi, Aydin; Murdoch, steven; Zacharias, Thomas; (2021) Recurring Contingent Payment for Proofs of Retrievability. (Paper 2021/1145 ). Cryptology ePrint Archive Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/10153741/1/2021-1145.pdf