Lab 07 · Timing & uncertainty · 30–40 minutes
Q-Day: The Migration Window
Use Mosca's inequality to explore how threat assumptions, data secrecy, and migration duration change the time available to act.
Fictional horizons, not Q-Day predictions · No account needed
The date is uncertain. The preparation still takes time.
“Q-Day” is shorthand for when a quantum computer could carry out a relevant cryptographic attack at a useful scale. It is not a known date, and different algorithms and targets need different capabilities. New research can change our assessment of the horizon; moving a slider does not change the actual technology.
X
Secrecy lifetime
How long newly created data must remain confidential. This is not simply how long a file is stored.
Y
Migration duration
Time for discovery, procurement, vendor support, testing, rollout, and retirement of vulnerable protection.
Z
Assumed threat horizon
Time from this scenario's baseline until the relevant quantum attack is assumed possible. An input for planning, not an output prediction.
Mosca's inequality: X + Y > Z
If secrecy lifetime plus migration duration exceeds the assumed threat horizon, the planning window is already too short. For example: data needs 5 years of secrecy, migration needs 3 years, and the assumed horizon is 7 years. That is 8 years of need against 7 years of assumed time.
Why add X after Y? Until migration finishes, the system may still create data protected by vulnerable cryptography. The last such data needs confidentiality for another X years. An adversary may capture it now and decrypt it later.
All values in this lab are fictional assumptions. A later upgrade does not retroactively protect previously captured ciphertext. The inequality is a warning framework, not a security guarantee or permission to wait.