Draft: draft-ietf-perc-srtp-ekt-diet

Commentary: , 
 Changes look good , except for few typos . 
 Nothing to add beyond Suhas ' comments . 
 Section 4 Each EKT cipher specifies a value T that is the maximum number of times a given key can be used . An endpoint MUST NOT send more than T Full EKT Field using the same EKTKey . In addition , the EKTKey MUST NOT be used beyond the lifetime provided by the TTL described in Section 3.2 . This document tells the sender to put the same EKT into 3 SRTP packets . This does not count as 3 encryptions . This is 1 encryption , even though the ciphertext is transmitted multiple times . 
 ektttl : The maximum amount of time , in seconds , that this ektkeyvalue can be used . The ektkey_value in this message MUST NOT be used for encrypting or decrypting information after the TTL expires . There is a mismatch between TTL and   says that the key can not be used after a number of seconds , but T says that the key can not be used after a number of encrypt operations . The data to enforce these is very different . This should be discussed in implementation guidance . 
 These functions have the property that  , E(K , P ) ) = ( P concatenated with optional padding ) for all values of K and P. Each cipher also has a limit T on the number of times that it can be used with any fixed key value . The EKTKey MUST NOT be used more that T times . Where is the counter kept to enforce T ? It does not seem to be one of the parameters associated with the SPI for outbound processing . Also , what does an implementation do if it reaches the limit imposed by T ?
Paragraph (version B):
When receiving a new EKTKey, implementations need to use the ekt_ttl
to create a time after which this key cannot be used and they also
need to create a counter that keeps track of how many times the keys
has been used to encrypt data to ensure it does not exceed the T
value for that cipher.  If either of theses limits are exceeded, the
key can no longer be used for encryption.  At this point
implementation need to either use the call signaling to renegotiation
a new session or need to terminate the existing session.  Terminating
the session is a reasonable implementation choice because theses
limits should not be exceeded except under an attack or error
condition.
Paragraph (version A):
These functions have the property that D(K, E(K, P)) = ( P
concatenated with optional padding) for all values of K and P.  Each
cipher also has a limit T on the number of times that it can be used
with any fixed key value.  The EKTKey MUST NOT be used more that T
times.
Paragraph (version B):
These functions have the property that D(K, E(K, P)) = ( P
concatenated with optional padding) for all values of K and P.  Each
cipher also has a limit T on the number of times that it can be used
with any fixed key value.  The EKTKey MUST NOT be used for encryption
more that T times.  Note that if the same EKT packet is retransmitted
3 times, that only counts as 1 encryption.
Paragraph (version A):
Each EKT cipher specifies a value T that is the maximum number of
times a given key can be used.  An endpoint MUST NOT send more than T
Full EKT Field using the same EKTKey.  In addition, the EKTKey MUST
NOT be used beyond the lifetime provided by the TTL described in
dtls-srtp-extensions.
Paragraph (version B):
Each EKT cipher specifies a value T that is the maximum number of
times a given key can be used.  An endpoint MUST NOT encrypt more
than T different Full EKT Field using the same EKTKey.  In addition,
the EKTKey MUST NOT be used beyond the lifetime provided by the TTL
described in dtls-srtp-extensions.