Solutions to security problems, particularly ones involving cryptography, have typically been approached through the Inside-Out Threat Model, "this is our solution and whatever it addresses is the threat". Email encryption/signing and SSL/TLS are two examples of the Inside-Out Threat Model, with the existence of a multi-billion dollar global cybercrime industry testifying to the fact that the threat-modelling performed during the design process was aimed more at satisfying the cryptographers' rather than the end users' needs. This paper looks at the application of problem-structuring methods or PSMs, a technique from the field of social planning, to address computer security problems, not so much to define technical solutions but to help analyse the problem so that the most appropriate, rather than simply the most technologically trendy, solution is applied to the problem.

Although there have been various proposals to build large-scale PKIs, there appears to be no research publicly available on the underlying certificate store which will be required to support such a PKI. This paper analyses the requirements for, and presents the design of a general-purpose certificate store which places few constraints on the underlying computer hardware or operating system used, provides a high degree of scalability (from single end users up to the corporate/CA level), and provides the level of reliability, availability and error recovery required of such an application and stipulated in a number of standards which cover CA operation.