Einstein, in his 1905 paper On the Electrodynamics of Moving Bodies, famously uses two postulates to derive the Lorentz transformations:

1. The relativity postulate: the laws of physics are invariant in all inertial frames.
2. The light-speed postulate: that the speed of light in vacuum is the same in all inertial frames.

How are these postulates used to show that no signal may propagate faster than light?