title: A secure protocol for protecting the identity of providers when disclosing data for disease surveillance.
abstract: BACKGROUND
  Providers have been reluctant to disclose patient data for public-health purposes. Even if patient privacy is ensured, the desire to protect provider confidentiality has been an important driver of this reluctance.
  
  
  METHODS
  Six requirements for a surveillance protocol were defined that satisfy the confidentiality needs of providers and ensure utility to public health. The authors developed a secure multi-party computation protocol using the Paillier cryptosystem to allow the disclosure of stratified case counts and denominators to meet these requirements. The authors evaluated the protocol in a simulated environment on its computation performance and ability to detect disease outbreak clusters.
  
  
  RESULTS
  Theoretical and empirical assessments demonstrate that all requirements are met by the protocol. A system implementing the protocol scales linearly in terms of computation time as the number of providers is increased. The absolute time to perform the computations was 12.5&emsp14;s for data from 3000 practices. This is acceptable performance, given that the reporting would normally be done at 24&emsp14;h intervals. The accuracy of detection disease outbreak cluster was unchanged compared with a non-secure distributed surveillance protocol, with an F-score higher than 0.92 for outbreaks involving 500 or more cases.
  
  
  CONCLUSIONS
  The protocol and associated software provide a practical method for providers to disclose patient data for sentinel, syndromic or other indicator-based surveillance while protecting patient privacy and the identity of individual providers.
authors.affiliation: Children's Hospital of Eastern Ontario Research Institute, Ottawa, Ontario, Canada. kelemam@uottawa.ca
authors.forename: Khaled
authors.initials: K
authors.lastname: El Emam
authors.forename: Jun
authors.initials: J
authors.lastname: Hu
authors.forename: Jay
authors.initials: J
authors.lastname: Mercer
authors.forename: Liam
authors.initials: L
authors.lastname: Peyton
authors.forename: Murat
authors.initials: M
authors.lastname: Kantarcioglu
authors.forename: Bradley
authors.initials: B
authors.lastname: Malin
authors.forename: David
authors.initials: D
authors.lastname: Buckeridge
authors.forename: Saeed
authors.initials: S
authors.lastname: Samet
authors.forename: Craig
authors.initials: C
authors.lastname: Earle
mesh_terms: D016494:Computer Security; D003219:Confidentiality; D018563:Disease Notification; D004196:Disease Outbreaks / Q000517:prevention & control*; D006801:Humans; D011159:Population Surveillance