The VIGIK system is quite misunderstood overall.
In France, most people live in appartment buildings, so the letter-boxes are not on the street. As such, the post office needs some way to enter the building to deliver mail. Originally, they used a mechanical key, that was universal across the country. The key was copied heavily, which meant that anyone could (and did) get access to buildings.
This mechanical key was replaced by the VIGIK system. "Services", such as the post, power company, etc can get access to buildings using a SERVICE BADGE. The SERVICE BADGES are MIFARE 1K Classic badges.
RESIDENTS of buildings also have badges. These are also based on MIFARE 1k Classic.
Each access control manufacturer (In France, basically: Intratone & Hexact (COGELEC), Comelit, Noralsy, Urmet and some other smaller brands) build their own hardware. Each RESIDENTIAL BADGE uses a data format and keys that are individual to the manufacturer (and make, model, etc of the reader). A RESIDENTIAL BADGE can open just the door it's authorised to open. Contrary to common vernacular, these are NOT VIGIK badges. They are residential badges.
A "VIGIK" badge, or more correctly, a SERVICE BADGE is a temporary badge. There are 1024-byte RSA Public Keys embedded into the access control readers. Each SERVICE has its own public key (La Poste, EDF, Orange, etc). All Access Control Systems in France are loaded with La Poste, EDF, Orange public keys by default.
A SERVICE BADGE has to be written at least every 84 hours, but typically daily. It includes data: (in "clear") the SERVICE ID, date written, any special restrictions, etc. There is signature data: This is the "clear" data which is encrypted via the SERVICE's Private Key.
When a SERVICE BADGE is placed on a reader, the reader checks the data and validates that the SIGNATURE is correct to ensure that the data wasn't forged. If there's a match, the door opens. If there's no match, the door doesn't open. SERVICE badges "expire" after a max of 84 hours, or the time limit included in the data (but never over 84 hours) So, even if someone steals / copies a SERVICE BADGE, they don't have permanent access.
There have been no new VIGIK keys for a long time: the A-key is 314B49474956 / "1KIGIV" for the data blocks, and "A0A1A2A3A4A5" for the other blocks.
TL:DR; Residential badges are not "VIGIK" badges. They're just MF Classic 1k badges that use a data format proprietary to their manufacturer / model / etc. "VIGIK" badges are SERVICE badges. They use RSA encryption in the datablocks to provide secure temporary access to all buildings.
A SERVICE BADGE has to be written at least every 84 hours, but typically daily. except for emergency, they have no time to prepare keys in case of intervention, so there is no 84h limitation
The 84 hours is a hard limit in the protocol. The emergency teams of GDRF scan their badges daily when they get to the office.
You can get more info on that side here : https://www.vigik.com/presentation-de-vigik (in French)
kwx(kwx____) on the Flipper Devices discord: https://discord.com/channels/740930220399525928/954422716138676254/1005012143923535902