Rube Goldberg Fun:
So you need to get through a door in the rear future. The question is, how difficult you want to make opening it. Keys? Seriously? Let's start with a proximity device either implanted or worn by all guards. It might need to work in tandem with another implanted in the prisoner so the door won't open if the prisoner is less than five feet away, but more than ten (no prisoner behind the door, and a prisoner holding a guard hostage is too close and disables door opening).
You might need TWO guards with unique chips to open the door - no one guard should be moving prisoners without another guard to back them up AND watch them so they don't do anything inappropriate. You might disable guards and take their chips, so the chips 'fry' if they can't continuously detect the biorhythms of the guard. Here is where a key might come in handy. Swipe the key so the door knows you want to open it, but the other stuff verifies you are authorized to use the door.
For sensitive steps, like moving high security prisoners or leaving the prison, an additional retinal scan should be needed (again, requiring a matching chip nearby to verify ID) If a retinal scan is too ordinary, use a DNA sampling technique like in GATTACA. Voice recognition software is an option, but it's pretty ordinary. Each guard could have an individual numeric code they enter into a keypad, but the keypad is also scanning fingerprints and thermal imaging the veins in their hands to see if they really are the right person.
The guards should have "panic" codes that still open the doors but alert the security that they are being forced to open doors. So even clever gate crashers might get codes and workarounds that still ultimately trip security and lead to an ambush at the most inopportune time. Forcing guards to let you in may still allow them to betray you and alert security.
Even in all of this, there is still room for deviousness. So if disease is a concern, thermal imaging locks down all doors if anyone has a fever. Micro-PCR tests for both the DNA of the guards AND for the presence of viruses, so at certain steps, they might have to wait 10-20 min for a device to finish testing before allowing passage. Unauthorized access might not be stopped by guards, but instead by lethal doses or radiation from sterilization devices (you don't even know you're dying until you've already escaped, but your prisoner doesn't get far).
So the key is a tiny step for a really high-tech process. Now how about ordinary tech? A guard has to buzz you in. Everything has two independent cameras watching everywhere at all times. Walls have sensors to detect if they are breached (this could be a simple mesh of fine wire that alarms if broken or as complex as vibration sensors, thermal sensors, etc). The appropriate paperwork has to be filed before ANY of these doors are authorized to open, even if the right guards show up with the right chips, DNA and (yes) keys.
