Pebbling and Proofs of Work

  • Cynthia Dwork
  • Moni Naor
  • Hoeteck Wee
Part of the Lecture Notes in Computer Science book series (LNCS, volume 3621)


We investigate methods for providing easy-to-check proofs of computational effort. Originally intended for discouraging spam, the concept has wide applicability as a method for controlling denial of service attacks. Dwork, Goldberg, and Naor proposed a specific memory-bound function for this purpose and proved an asymptotically tight amortized lower bound on the number of memory accesses any polynomial time bounded adversary must make. Their function requires a large random table which, crucially, cannot be compressed.

We answer an open question of Dwork et al. by designing a compact representation for the table. The paradox, compressing an incompressible table, is resolved by embedding a time/space tradeoff into the process for constructing the table from its representation.


Hash Function Memory Access Main Memory Random Oracle Cache Size 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2005

Authors and Affiliations

  • Cynthia Dwork
    • 1
  • Moni Naor
    • 2
  • Hoeteck Wee
    • 3
  1. 1.Microsoft Research
  2. 2.Weizmann Institute of Science 
  3. 3.University of CaliforniaBerkeley

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