If the Government promotes or requires the use of an application for personal computing devices the source code for these applications and of any server-side components with which they work should be made available for public scrutiny.
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The public must be confident that any app is secure and not invading their privacy to maximise uptake.
Open sourcing permits Validation of the security of any app(s) by independent experts as well as feedback from the wider community of experts.
The involvement of corporate entities with poor records on data privacy has already resulted in mistrust towards such efforts which can be readily assuaged by open sourcing. Privacy guarantees should be engineered into any such application.