I found in the RFC about TLS v1.2 that master_secret is computed this way:
master_secret = PRF(pre_master_secret, "master secret", ClientHello.random + ServerHello.random)
while, subsequently, the needed key blocks composing the key material are generated through
key_block = PRF(SecurityParameters.master_secret, "key expansion", SecurityParameters.server_random + SecurityParameters.client_random);
And here it is my question: is there any difference between SecurityParameters.server_random and ServerHello.random or between the corresponding client's random numbers? And if yes, what is this difference?
My opinion: I think SecurityParameters.master_secret is the one computed with the first PRF shown above: so - supposing this "asymmetry" of notation - maybe, also the random numbers in the second PRF are the same used in the first? But, if so, why this different notation?