[CST-2] Security - Concept of Perfect Secrecy

[Matt Shreeve]

Hello
Slide 81 of the Security notes defines perfect secrecy in terms of entropy 
(H(P)=H(P|C)), and then proves Shannon's implication (H(K)>=H(P)).  Does 
anyone know (or, better, provide a proof) that the reverse implication is 
true? ie

H(K)>=H(P) => H(P)=H(P|C)

Cheers,

Matt