# One Time Pad proof for Perfect Secrecy

In the book "Introduction to Cryptography with Coding Theory" by Trappe, in the paragraph about the security of the One Time Pad, is it told that given the set of possible plaintexts $$P$$, the set of possible keys $$K$$ and the set of possible ciphertext $$C$$, then:

$$H(P,K,C)=H(P,K)=H(P,C)$$

However, he doesn't explain why. Can you show me ? If possible also formally

• What does the function $H$ represent? – Maarten Bodewes Nov 24 '19 at 10:44