4) The tag first verifies whether this message is originated
from the TTP by computing F(PIN) Gn PIN.
If it succeeds, the tag computes G0
n = P(Gn), G00n =P(G0n), K0n= F(Kn), and K00n = F(K0n). Finally, tags
computes the messages K0n
G0
n, K00
n G00
n and Kt =
F(Gn Gn+1), and sends them to the reader.
5) The reader forwards these messages to the TTP.