To automate the time-consuming invoice verification process, a large number of complex matching algorithms have been developed and networked for VESTIGAS. Using advanced fuzzy approaches, these check not only factual invoice features (invoice addressee, tax key, etc.), but all invoice items. In an expansion stage, the check can even be extended to a complete price comparison and pre-assignment.
In order to be able to perform an automated invoice verification, it requires important meta data for legal certainty as part of the signature. Ordinary screen signatures are not sufficient for this purpose. For this reason, VESTIGAS relies on a cryptographic electronic signature based on future-proof X.509 certificates for ECDSA prime256v1 signatures. Each user receives a personal certificate issued by VESTIGAS on the mobile application. This procedure is in line with the applicable eIDAS regulations.
To guarantee the integrity of the delivery bills beyond any doubt, VESTIGAS uses blockchain technology, which is gaining in importance. Each individual delivery bill represents a separate series of data blocks, which are serially linked via hashes (SHA-3). A new block is generated for each adjustment of the delivery bill. In addition to the actual change, this also contains a hash of the previous block and the tamper-proof signature of the creator. Since this links all blocks together, the integrity of the entire block chain can be ensured and manipulations can be detected.
The VESTIGAS app supports the use of Bluetooth Low Energy (BLE) to further simplify the transfer of delivery bills between process participants. In contrast to classic solutions such as QR codes or NFC, handover can take place contactlessly over a range of up to 30 meters, even at construction sites without Internet. Intensive development has made it possible to fully automate the device coupling and transmission process without having to involve manual steps.