Situation: Information management enables humanitarian organizations to make adequate interventions based on timely, appropriate and trustworthy information. A crucial type of information are identities, because they can be used to assess vulnerability and efficiently manage aid distribution. Vulnerability determines who receives aid first because resources are always limited. This information is increasingly being stored and processed in identity systems. Complication: Most identity systems are centralized and produce analogue proofs of identity such as passports or ID cards. These systems are susceptible to privacy and data breaches. Centralization leads to single-points-of-failure and could lead to fraudulent behavior resulting in people lacking formal proofs of identity. In general there is limited interoperability between identity systems and limited collaboration between the owners of these systems. Approach: To create an interoperable and shared digital identity system using a Design Science Research strategy and systems engineering approach. This system must be distributed, protect privacy and put the identity owner in control of his or her data. The foundation of the system consists of Humanitarian Information Management principles, Privacy-by-Design principles and Self-Sovereign Identity principles. This research creates a functional blockchain based system, that enables identities for the use-case of Cash Transfer Programs. Results: We present a validated set of ten design decisions that represent the trade-offs that have been made and prescribe a blueprint for a technical design. Next steps:Future research should be done on how such a system could be implemented and used. This would require a process design approach that has to be developed, Also, elaborate research into user experience and user interfaces should be conducted.