Paper 2018/300

Outsourcing Modular Exponentiation in Cryptographic Web Applications

Pascal Mainini and Rolf Haenni


Modern web applications using advanced cryptographic methods may need to calculate a large number of modular exponentiations. Performing such calculations in the web browser efficiently is a known problem. We propose a solution to this problem based on outsourcing the computational effort to untrusted exponentiation servers. We present several efficient outsourcing protocols for different settings and a practical implementation consisting of a JavaScript client library and a server application. Compared to browser-only computation, our solution improves the overall computation time by an order of magnitude. This is an extended version of a paper accepted and presented at the Voting’18 workshop of the Financial Cryptography and Data Security 2018 conference. It will be included in the conference’s LNCS proceedings and available on the Springer web site.

Available format(s)
Cryptographic protocols
Publication info
Published elsewhere. Major revision. 22th International Conference on Financial Cryptography and Data Security (FC 2018)
Internet votingModular exponentiationsJavaScript cryptographyOutsourcing algorithms
Contact author(s)
pascal mainini @ bfh ch
2018-04-02: received
Short URL
Creative Commons Attribution


      author = {Pascal Mainini and Rolf Haenni},
      title = {Outsourcing Modular Exponentiation in Cryptographic Web Applications},
      howpublished = {Cryptology ePrint Archive, Paper 2018/300},
      year = {2018},
      note = {\url{}},
      url = {}
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