Saltzer and Schroeder's design principles

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Saltzer and Schroeder's design principles are design principles enumerated by Jerome Saltzer and Michael Schroeder in their 1975 article The Protection of Information in Computer Systems,[1] that from their experience are important for the design of secure software systems.

The design principles[edit]

  • Economy of mechanism: Keep the design as simple and small as possible.
  • Fail-safe defaults: Base access decisions on permission rather than exclusion.
  • Complete mediation: Every access to every object must be checked for authority.
  • Open design: The design should not be secret.
  • Separation of privilege: Where feasible, a protection mechanism that requires two keys to unlock it is more robust and flexible than one that allows access to the presenter of only a single key.
  • Least privilege: Every program and every user of the system should operate using the least set of privileges necessary to complete the job.
  • Least common mechanism: Minimize the amount of mechanism common to more than one user and depended on by all users.
  • Psychological acceptability: It is essential that the human interface be designed for ease of use, so that users routinely and automatically apply the protection mechanisms correctly.
  • Work factor: Compare the cost of circumventing the mechanism with the resources of a potential attacker.
  • Compromise recording: It is sometimes suggested that mechanisms that reliably record that a compromise of information has occurred can be used in place of more elaborate mechanisms that completely prevent loss.


  1. ^ Smith, R. E. (November 2012). "A Contemporary Look at Saltzer and Schroeder's 1975 Design Principles". IEEE Security Privacy. 10 (6): 20–25. doi:10.1109/MSP.2012.85. ISSN 1540-7993. S2CID 13371996.
  • [1] The resources of the Industrial Internet Consortium – Volume 4 Industrial IoT Chapter 7.9 FROM FUNCTIONAL TO IMPLEMENTATION VIEWPOINT page 58]