  Individuals lack oversight over systems that process their data. This can
lead to discrimination and hidden biases that are hard to uncover. Recent data
protection legislation tries to tackle these issues, but it is inadequate. It
does not prevent data misusage while stifling sensible use cases for data. We
think the conflict between data protection and increasingly data-based systems
should be solved differently. When access to data is given, all usages should
be made transparent to the data subjects. This enables their data sovereignty,
allowing individuals to benefit from sensible data usage while addressing
potentially harmful consequences of data misusage. We contribute to this with a
technical concept and an empirical evaluation. First, we conceptualize a
transparency framework for software design, incorporating research on user
trust and experience. Second, we instantiate and empirically evaluate the
framework in a focus group study over three months, centering on the user
perspective. Our transparency framework enables developing software that
incorporates transparency in its design. The evaluation shows that it satisfies
usability and trustworthiness requirements. The provided transparency is
experienced as beneficial and participants feel empowered by it. This shows
that our framework enables Trustworthy Transparency by Design.
