{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,22]],"date-time":"2026-10-22T16:04:23Z","timestamp":1792685063381,"version":"4.5.0"},"reference-count":24,"publisher":"Association for Computing Machinery (ACM)","issue":"2","content-domain":{"domain":["dl.acm.org"],"crossmark-restriction":true},"short-container-title":["ACM Trans. Internet Technol."],"published-print":{"date-parts":[[2005,5]]},"abstract":"<jats:p>A resource may be abused if its users incur little or no cost. For example, e-mail abuse is rampant because sending an e-mail has negligible cost for the sender. It has been suggested that such abuse may be discouraged by introducing an artificial cost in the form of a moderately expensive computation. Thus, the sender of an e-mail might be required to pay by computing for a few seconds before the e-mail is accepted. Unfortunately, because of sharp disparities across computer systems, this approach may be ineffective against malicious users with high-end systems, prohibitively slow for legitimate users with low-end systems, or both. Starting from this observation, we research moderately hard functions that most recent systems will evaluate at about the same speed. For this purpose, we rely on memory-bound computations. We describe and analyze a family of moderately hard, memory-bound functions, and we explain how to use them for protecting against abuses.<\/jats:p>","DOI":"10.1145\/1064340.1064341","type":"journal-article","created":{"date-parts":[[2005,8,3]],"date-time":"2005-08-03T08:30:55Z","timestamp":1123057855000},"page":"299-327","update-policy":"https:\/\/doi.org\/10.1145\/crossmark-policy","source":"Crossref","is-referenced-by-count":102,"title":["Moderately hard, memory-bound functions"],"prefix":"10.1145","volume":"5","author":[{"given":"Martin","family":"Abadi","sequence":"first","affiliation":[{"name":"University of California at Santa Cruz, Santa Cruz, CA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mike","family":"Burrows","sequence":"additional","affiliation":[{"name":"Google, Mountain View, CA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mark","family":"Manasse","sequence":"additional","affiliation":[{"name":"Microsoft Research, Mountain View, CA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ted","family":"Wobber","sequence":"additional","affiliation":[{"name":"Microsoft Research, Mountain View, CA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"320","published-online":{"date-parts":[[2005,5]]},"reference":[{"key":"e_1_2_1_1_1","volume-title":"Lecture Notes in Computer Science","volume":"2896","author":"Abadi M."},{"key":"e_1_2_1_2_1","volume-title":"Proceedings of NDSS 2003 (Networks and Distributed Systems Security). 25--39","author":"Abadi M."},{"key":"e_1_2_1_3_1","unstructured":"Abadi M. Lomas T. M. A. and Needham R. 1997. Strengthening passwords. SRC Technical Note 1997--033 Digital Equipment Corporation Systems Research Center. September\/December.  Abadi M. Lomas T. M. A. and Needham R. 1997. Strengthening passwords. SRC Technical Note 1997--033 Digital Equipment Corporation Systems Research Center. September\/December."},{"key":"e_1_2_1_4_1","volume-title":"Proceedings of the Nineteenth Annual ACM Symposium on Theory of Computing. 305--314","author":"Aggarwal A."},{"key":"e_1_2_1_5_1","volume-title":"CAPTCHA: Using hard AI problems for security. In Advances in Cryptology---EUROCRYPT","author":"Ahn L.","year":"2003"},{"key":"e_1_2_1_6_1","unstructured":"Astley M. R. 2001. Repost of private mail re: No free spam. Posting available on the web at URL www.camram.org\/mhonarc\/spam\/msg00030.html.  Astley M. R. 2001. Repost of private mail re: No free spam. Posting available on the web at URL www.camram.org\/mhonarc\/spam\/msg00030.html."},{"key":"e_1_2_1_7_1","unstructured":"Back A. 1997. HashCash. Available on the web at URL www.cypherspace.org\/~adam\/hashcash.  Back A. 1997. HashCash. Available on the web at URL www.cypherspace.org\/~adam\/hashcash."},{"key":"e_1_2_1_8_1","unstructured":"CAMRAM 2002. Welcome to CAMRAM. Available on the web at URL www.camram.org.  CAMRAM 2002. Welcome to CAMRAM. Available on the web at URL www.camram.org."},{"key":"e_1_2_1_9_1","doi-asserted-by":"publisher","DOI":"10.1145\/280324.280336"},{"key":"e_1_2_1_10_1","volume-title":"Lecture Notes in Computer Science","volume":"2729","author":"Dwork C."},{"key":"e_1_2_1_11_1","volume-title":"Advances in Cryptology---CRYPTO '92","author":"Dwork C."},{"key":"e_1_2_1_12_1","doi-asserted-by":"publisher","DOI":"10.1137\/S0097539795280512"},{"key":"e_1_2_1_13_1","volume-title":"Eds. 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