A disclosed method is implemented by a voucher server for distributing digital vouchers. The voucher server stores a plurality of encrypted digital vouchers, each being encrypted with a respective one of a plurality of encryption keys and each having an associated identifier. The voucher server receives, from a computing device, a request for a digital voucher, the request including an identifier. The voucher server determines if the received identifier matches an identifier of any of the plurality of encrypted digital vouchers. If the received identifier matches an identifier for a given one of the encrypted digital vouchers, the voucher server transmits the given encrypted digital voucher to the computing device. The voucher server does not have access to the encryption key used to encrypt the given encrypted digital voucher.