The app implements the specifications contained in the ICAO TECHNICAL REPORT: Visible Digital Seals for Non Electronic Documents, v.17, March 2018. A Visible Digital Seal is a digitally signed 2d barcode. This means that the app scans a 2d barcode, extracts the data from the barcode and verifies the digital signatures. It downloads certificates (via HTTP or HTTPS) from a defined certificate repository and uses these certificates to validate the signature. The ICAO TR recommends “ECDSA with a key length of at least 256 bit in combination with SHA-256” for the digital signature (pag. 13 of the ICAO TR).
