Can we use Ke or Kd forever? How long then? How do we determine it?
Unicity distance tells us it is ‘breakable’ after 2.6 times the key length
Other methods of assessing exposure associated with a key:
- Potential damage from one key’s theft?
- Number of exposures encountered?
- Time to guess the key by exhaustion?
- Change in keyholders?
- Number of missing keys and their import?