Erratum 5127

Addresses issue #1

section-5.md

@@ -47,15 +47,21 @@
    length is 64 octets.  Optional data parameter is not used in the
    derivation.
 
-     IMSK = First 32 octets of TLS-PRF(EMSK, "TEAPbindkey@ietf.org" |
-     "\0" | 64)
-
-     where "|" denotes concatenation, EMSK is the EMSK from the inner
-     method, "TEAPbindkey@ietf.org" consists the ASCII value for the
-     label "TEAPbindkey@ietf.org" (without quotes), "\0" = is a NULL
-     octet (0x00 in hex), length is the 2-octet unsigned integer in
-     network byte order, and TLS-PRF is the PRF negotiated as part of
-     TLS handshake [RFC5246].
+     IMSK = First 32 octets of TLS-PRF(EMSK, "TEAPbindkey@ietf.org",
+     0x00 | 0x00 | 0x40)
+
+     where "|" denotes concatenation and the TLS-PRF is defined in
+     [RFC5246] as 
+     
+     PRF(secret, label, seed) = P_<hash>(secret, label | seed).
+
+     the secret is the EMSK from the inner method, the label is 
+     "TEAPbindkey@ietf.org" consisting of the ASCII value for the
+     label "TEAPbindkey@ietf.org" (without quotes),  the seed 
+     consists of the "\0" null delimiter (0x00) and 2-octet unsigned 
+     integer length in network byte order (0x00 | 0x4) specified 
+     in [RFC5295].
+
 
    If an inner method does not support export of an Extended Master
    Session Key (EMSK), then IMSK is the MSK of the inner method.  The