Wimax standards and Security The Wimax

Appendix IV: Dot16KDF for PKMv2
The Dot16KDF algorithm is a counter mode encryption (CTR) construc- tion that may be used to derive an arbitrary amount of secret key from source keying material. The algorithm to acquire HMAC is defined by the following:
Dot16KDF(key, astring, keylength) // generate a keylength-bit long secret key from astring
// encrypted with key
{
result = null;
Kin = Truncate (key, 160);
For (i = 0; i <= int( (keylength-1)/160 ); i++){
result = result | SHA-1( i| astring | keylength | Kin); //encrypted astring with key using SHA-1

return Truncate (result, keylength);
}

The key is a cryptographic key that is used by the underlying digest algo- rithm SHA-1; astring is an octet string used to generate the secret key; and keylength is the length of the secret key to be generated.

Truncate (key, y) is to retrieve the rightmost y bits (y LSBs) of the key only if y is less than or equal to the length of the key.





References

1. 
   IEEE Std. 802.16-2001, IEEE Standard for Local and Metropolitan Area Networks— Part 16: Air Interface for Fixed Broadband Wireless Access Systems, IEEE, 2001.
   
2. 
   IEEE Std. 802.16-2004, IEEE Standard for Local and Metropolitan Area Networks— Part 16: Air Interface for Fixed Broadband Wireless Access Systems, IEEE, 2004.
   
3. 
   IEEE Std. 8802.16e-2005, IEEE Standard for Local and Metropolitan Area Networks—