DES vs. DES OFB

[ASTROMODAT]

Our existing UHF conventional XTS Model III portables and ASTRO Spectra mobile radios are currently running DES and are "ASTRO Ready" (analog operation). We are using RSS 6.50, and I suppose we should upgrade to the latest CPS.

We plan to FLASH upgrade to ASTRO Digital operation, and we must be APCO 25 compliant. I understand that that this will entail the Q806 and G806 FLASH upgrades, respectively (not cheap---$500 for ea XTS, and $550 for ea Spectra mobile).

I also understand that we will need to change from DES to DES-OFB, so we can run DES on ASTRO digital and be APCO/Project 25 compliant.

My question is: Must we make hardware changes? The current R3 pricebook shows a price of $749 for the XTS and $749 for Spectra DES-OFB operation. I can't tell if this means we need new encryption hardware modules, or whether we can simply (but expensively!) FLASH upgrade our existing DES hardware modules to DES-OFB. Do we need to open the radios and replace the encryption modules, or can we simply FLASH upgrade from DES to DES-OFB? We do NOT have Multikey nor OTAR options.

I assume that our T3011DX key loaders (with DES/DES XL) will NOT be able to have just a module change to DES-OFB, and we will need to go to the new KVL 3000?

Thanks, in advance, for any help on this!

Larry

[Pj]

We are currently doing upgrades like you are doing, except I think we were quoted a little more from analog to IMBE.

You can use DES, DES-XL, DVP/XL etc in the ASTRO mode. It won't be APCO25 compliant, but you can use it. All the -OFB modules will do is bring your radio system into the APCO25 standard when encrypted.

You cannot FLASHupgrade the modules, but you may be able to get a trade in credit. We have DVP-XL modules, and we are sticking with them. They will work 100% in the Astro mode and in Astro encrypted mode.

Unless there is another agency that needs to transmit on your channel WITH encyption on their radio's, I wouldn't worry about it.

Again, acording to Motorola and the APCO standard, the -OFB is only required to meet the standard while transmitting encrypted.

[ASTROMODAT]

Thanks for the clarification and info, Pj! Makes good sense.

Larry

[XDCLabs.COM]

I assume that our T3011DX key loaders (with DES/DES XL) will NOT be able to have just a module change to DES-OFB, and we will need to go to the new KVL 3000?

Your DX KVLs will load DES-OFB keys with any changes. The same DES key can be used in CFB, XL and OFB modes. Of couse they won't interoperate, but it is the samy keying material.

[ASTROMODAT]

Is it necessary that I change my encryption modules in my T3011DX keyloaders from their current DES/DES-XL to DES-OFB, so that I can load ASTRO radios with DES-OFB? If the answer is "Yes," I have never seen a DES-OFB encryption module for a T3011DX KVL.

Larry

[XDCLabs.COM]

You don't have to do anything to your KVL. Both DES-XL and DES-OFB use the same DES key. XL and OFB are just different implementations of the DES algorithm and use the same type of key.

[Pj]

Unless I am thinking of something else, isnt' there a DES/-XL loader and a DVP/-XL loader? I thought there were two different loaders for the two.

[ASTROMODAT]

Pj, I believe you are talking about a different issue in that DES schemes use a 56 bit key, whereas DVP is a 32 bit key. So, I believe this would require a module change.

Larry