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Re: [STDS-802-16-MOBILE] Please clarify section 7.8.4.1.1 from P80216e/D8



Hi,

 

  1. make sure no more than one CTR-encrypted PDU is in a given frame (or else the scheme is insecure)
  2. the counter (the AES (block) counter not the ROC), gets incremented whenever a new AES plaintext block is processed (an AES plaintext block has 16 bytes which is far less than a potential text size in a PDU)
  3. As the last quoted sentence says when the frame number rolls from 0xffffff to 0x000000 the ROC should be incremented

 

Ilan Zohar

Intel

 


From: owner-stds-802-16-mobile@ieee.org [mailto:owner-stds-802-16-mobile@ieee.org] On Behalf Of venkateshwarlu.v
Sent: Wednesday, June 15, 2005 11:01 AM
To: STDS-802-16-MOBILE@listserv.ieee.org
Subject: [STDS-802-16-MOBILE] Please clarify section 7.8.4.1.1 from P80216e/D8

 

Hi all,

I have been looking at the P802.16e/d8 specifications and got a doubt on Encryption notes given in the document, related to 8-bit rollover counter functionality.

 

Copied from standard page Number- 234

NOTE—When we start to deal with a new PDU we have a new frame number and therefore reinitialize the counter.

When the frame number reaches 0x000000 (from 0xFFFFFF), we increment ROC.

 

From the above Notes:

1- Whenever there is a new PDU, how it's possible to have a new frame number?

2- If we re-initialize the counter for every PDU, when this counter will be incremented?

3- When to increment the ROC.

 

I would really appeciate, if some one could clarify this.

 

Regds,

Venkat