Supply chain management is hampered by a lack of information sharing among partners. Information is not shared as organizations in the supply chain do not have direct contact and/or do not want to share competitive and privacy sensitive information. In addition, companies are often part of multiple supply chains and trading partners vary over time. Blockchains are distributed ledgers in which all parties in a network can have access to data under certain conditions. Private blockchains can be used to support parties in making their demand data directly available to all other parties in their supply chain. These parties can use this data to improve their planning and reduce the bullwhip effect. However, the transparency that blockchain technology offers makes it more difficult to protect sensitive data. The dynamics between these properties are not well understood. In this paper, we design and evaluate a blockchain architecture to explore its feasibility for reducing information asymmetry, while at the same time protecting sensitive data. We found that blockchain technology can allow parties to balance their need for inventory management with their need for flexibility for changing partners. However, measures to protect sensitive data lead either to reduced information, or to reduced speed by which the information can be accessed.