  A marketplace is defined where the private data of suppliers (e.g.,
prosumers) are protected, so that neither their identity nor their level of
stock is made known to end customers, while they can sell their products at a
reduced price. A broker acts as an intermediary, which takes care of providing
the items missing to meet the customers' demand and allows end customers to
take advantages of reduced prices through the subscription of option contracts.
Formulas are provided for the option price under three different probability
models for the availability of items. Option pricing allows the broker to
partially transfer its risk on end customers.

Cryptography and Security