My question is about how difficult is for someone having compromised the PSK and sniff all (DT)LS handshake, (so getting the NONCE), to get the encryption keys?
I understand :
getting the pre-master secret is straight forward
but then, what about the master secret MS?
because MS is calculated with PRF_HMAC_SHA256 which generates different MS for each sessions , how easy can it be for an attacker to re-calculate the right MS, then the encryption keys?