In the current 1.3 draft, section 6.3.4.3 specifies the content of the Finished
message. It contains this specification for key computation:
client_finished_key =
HKDF-Expand-Label(BaseKey, "client finished", "", L)
server_finished_key =
HKDF-Expand-Label(BaseKey, "server finished", "", L)
I wonder what the zero length string actually means. Is it a null-terminated
string that would encode in binary as a one octet byte string of value 0, or an
empty string that would encode in binary as a zero length string?
There is one example of encoding a string in section 4.8.1, and the binary
representation shows the encoding of the final null byte. Is that a common
assumption?
Similarly, in the HKDF-Expand-Label, do we assume a final null byte for the
"label"?
-- Christian Huitema
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