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A trusted app that only you can control (e.g. your mobile bank app or a Govt ID app) to produce a committed value. This committed value holds the key information about your income statement (which this agency warrant is true) and you use this value to prove via the zero-knowledge proof system to the verifier (i.e. the housing agency) that you are eligible for the house. There’s so much more we can do with this powerful privacy-technology!