The invention provides a digital contract comprising a sealed package comprising: a header package comprising: rules defining any sealed packages to be included in said contract; a validating party who is to validate said header package; and a sealing party who is to seal said package; a body containing at least a portion of the content of the package; and a validating signature generated from said rules and said body according to a first key belonging to said validating party; any sealed packages defined in said rules; and a sealing signature generated from said header package and any of said sealed packages according to a first key belonging to said sealing party. Further provided is contract management software for generating, validating, exchanging and managing such contracts.