Digital Encryption w/ a standard DES-XL-DVP Module?

TXCAP · Post by **TXCAP** » Wed Nov 17, 2004 1:44 pm

I have a Astro Saber which in which I installed a DES-XL / DVP module. Radio Displays EMC 1: DES-XL EMC 2: DVP. I loaded our DES & DVP keys. When I tested the radio on our mixed-mode EFJ repeater I accidentally left the DES encryption on in P25 Mode and the P25 transmission was encrypted. Non- Key loaded radios received what sounded like a radio under water, and showed that it was receiving coded (Only while using the DES key) . Encrypted radios received the transmission clear. So do we not need to DES-OFB modules? Can we go round just getting DES modules??

mancow · Post by **mancow** » Wed Nov 17, 2004 3:19 pm

My question exactly. I mentioned this earlier when I found the same thing out accidentally in mixed mode operation. However, I could'nt get the other radio to receive the encrypted P25.

mancow

Post by **batdude** » Wed Nov 17, 2004 4:18 pm

this was a huge discussion some time ago.

des-xl will indeed encrypt astro / p25 voice.

the original line of thought was that since DES-OFB was released pretty much at the same time as "astro", that it was REQUIRED to encrypt P25.

this is not the case.

P25 voice can be encrypted using DES-XL, OFB, or AES-256.

doug

fireradio · Post by **fireradio** » Wed Nov 17, 2004 4:56 pm

Is there a significant difference in recovered voice quality compared to using DES-XL and OFB on Astro?

Post by **batdude** » Wed Nov 17, 2004 5:04 pm

negative.

encrypted astro voice sounds the same as plain, unencrypted astro voice.

since the signal is already digital, encrypting it has no impact on the recovered voice quality.

the biggest impact on astro voice quality is dependent upon the DSP revision of the radio. There is a HUGE difference between DSP 6 and DSP 8 - DSP 8 pretty much kicks butt.

for the encryption guru's out there, des (including XL) uses Cipher Feedback, while OFB uses Output Feedback.... who freakin' knows what that means. some of the VERY early astro secure modules were actually labeled "DES-CFB" instead of "XL"

biggest "good deal" here is that your built like a brick $hithouse T3011DX KVL will load XL, plain des, and OFB... it doesn't care.

doug

fireradio · Post by **fireradio** » Wed Nov 17, 2004 5:37 pm

Very cool. Too bad I don't have any secure-ready Astro equipment to play around with!

CTAMontrose · Post by **CTAMontrose** » Thu Nov 18, 2004 7:24 am

so correct me if im wrong, but is the following true (keeping in mind that all the scenarios below are talking about in ASTRO mode and using the same key):

User 1 has DES-XL, and User 2 has DES-XL, they can communicate in digital encrypted?

User 2 has DES-XL and user 2 has DES-OFB, they CANNOT communicate in digital encrypted?

Obviously XL -> XL and OFB -> OFB work in their native modes.

Post by **Wowbagger** » Thu Nov 18, 2004 7:46 am

There are different algorithm IDs for DES-XL, DES-OFB, Triple-DES, AES, and clear.

The transmitting radio puts the algid into the data stream. The receiving radio uses the algid and keyid to select the correct decryption algorithm and key.

So, if your radio is announcing DES-XL, the receiving radio can do DES-XL, and has the appropriate key loaded, you will decrypt the data.

Now, suppose a new algorithm comes out - all that is needed is for that algorithm to be assigned an algid and the radio software updated to know about the algid, and you are set.

There's only a couple of lines of code difference between DES-XL and DES-OFB, but that is enough to make them different.

CTAMontrose · Post by **CTAMontrose** » Thu Nov 18, 2004 7:55 am

ok so as long as both users have the same, they can communicate encrypted in ASTRO... interesting.

The Pager Geek · Post by **The Pager Geek** » Thu Nov 18, 2004 9:15 am

Flashback:
http://batboard.batlabs.com/viewtopic.p ... ight=desxl

tpg

CTAMontrose · Post by **CTAMontrose** » Thu Nov 18, 2004 9:24 am

hahaha tpg called me out on the "use the search button"

LMAO!!

mancow · Post by **mancow** » Thu Nov 18, 2004 6:06 pm

OK, here's another vexing problem. I mentioned this in another thread before but I can't find it.

I have a racal radio that absolutely refuses to talk to a saber in analog des "securenet" mode UNLESS the key is all numerals. If any A-F characters are used in the key it won't work.

Ponder that one.

mancow

TXCAP · Post by **TXCAP** » Fri Nov 19, 2004 2:34 pm

Still havent got them talking' when you use those characters? After you told me bout it I tried it on the EFJ 5300 & 5100 and it worked great..... Must be something w/ Thales... Bye the way how's the portable........
MC

Post by **wavetar** » Fri Nov 19, 2004 2:40 pm

mancow wrote:OK, here's another vexing problem. I mentioned this in another thread before but I can't find it.

I have a racal radio that absolutely refuses to talk to a saber in analog des "securenet" mode UNLESS the key is all numerals. If any A-F characters are used in the key it won't work.

Ponder that one.

mancow

Assuming your Saber is ok with other radios, I'd say it's a question for Thales/Racal support.

Todd

vr2xst · Post by **vr2xst** » Tue Dec 21, 2004 6:17 pm

My Astro Saber II with DES loaded/Encrypted cannot communicate with regular Saber III with DES module. Anyone know why ?

73

fireradio · Post by **fireradio** » Tue Dec 21, 2004 8:11 pm

Maybe one of them has DES-XL enabled in the RSS while the other does not have -XL enabled?

The Pager Geek · Post by **The Pager Geek** » Tue Dec 21, 2004 8:17 pm

You must make sure the channel you are using is 100% non-astro in the astro saber's programming. You can't have "Mixed mode" RX on that channel, otherwise it defaults to secure astro as it's secure TX mode of TX'ing.

tpg

firemedic · Post by **firemedic** » Wed Dec 22, 2004 10:33 am

Ok, another question along these lines. We have 10 astro sabers with DES-XL/DES-OFB, and 6 more with just DES-XL. Can they talk to each other encrypted on the astro channels with just the DES-XL or am I screwed because of the OFB module and the radios will default to that? How do you select which it uses or can you? Just wondering as I'm still a little confused.

Post by **batdude** » Wed Dec 22, 2004 12:11 pm

no you are not "SCREWED"

enable this option in the OFB/XL equipped radios:

"ENABLE XL TRANSMIT"

this is in the SECURE tab of the conventional personality.

this forces XL to be the algo used on that channel.

doug

vr2xst · Post by **vr2xst** » Wed Dec 22, 2004 7:08 pm

Thanks all guys.

I hv check the RSS for my ASTRO Saber and Saber III asf:

1) both XL is disabled
2) non-astro mode is programmed in ASTRO Saber

But the problem still not 100% solved, i.e. my Saber III can heard my ASTRO Saber, on contrary my ASTRO Saber cannot heard any voice except the first MDC Signalling then keep silent ?

Anyone who hv same symtom and how to cure it ?

Thanks a lot

73

Post by **wavetar** » Wed Dec 22, 2004 7:25 pm

vr2xst wrote:Thanks all guys.

I hv check the RSS for my ASTRO Saber and Saber III asf:

1) both XL is disabled
2) non-astro mode is programmed in ASTRO Saber

But the problem still not 100% solved, i.e. my Saber III can heard my ASTRO Saber, on contrary my ASTRO Saber cannot heard any voice except the first MDC Signalling then keep silent ?

Anyone who hv same symtom and how to cure it ?

Thanks a lot

73

I've seen several posts in the past where one of the radios was either off frequency by 1 or 2 KHz, or the transmit deviation wasn't set properly in one of the radios...is the Astro Saber programmed with out-of-band frequencies?

Todd

vr2xst · Post by **vr2xst** » Thu Dec 23, 2004 2:47 am

Dear wavetar,

I HAVE NOT CHANGE ANY TRANSMIT DEVIATION ON BOTH HT'S BUT ONLY VCO DEVIATION TO INCREASE THE VALUE A LITTLE BIT FOR MY SABER III.

ANY COMMENT ?

73

vr2xst · Post by **vr2xst** » Sat Dec 25, 2004 1:10 am

NOW, I RE-CONFIG THE FLWG AND EVERYTHING OK !

SECURE DEV OFFSET CHANGED TO: 03
VCO DEV CHANGED TO: 0F

THANKS ALL GUYS

73

Post by **batdude** » Sat Dec 25, 2004 2:54 am

merry xmas (if you are christian)

NOW STOP YELLING AT US

that's what typing in all caps means

doug