Listening In- A Vietnam Vet Talks About Signal Collection in Combat Against the VC

Recently in Bangkok RGP had the privilege of sharing some cold barley soup with a US Vietnam War veteran.  He talked about collecting push-to-talk radio signals against the NVA and VC.

He said that in the very beginning of the war they had some success.  He said that one develops a sixth sense, that something did not feel right.  One night, he was feeling those little hairs on the back of his neck stand up, and so he went and turned on his radios and he noticed a very slight pop on one frequency, and so he waited.  Once in a while he heard a small noise on that one particular frequency and so he just kept waiting, listening.  He was in a small bunker with a candle, and the small noises became more frequent.  Then he heard a word, just one word, but he did not recognize it.  He said it was getting really late, and he just sat waiting, for hours.  The enemy was moving and keying the microphone by accident as they moved up.  He warned his Company Commander.  He said the small noises got clearer and clearer, and then when the attack started the voice was so clear that it sounded like that VC soldier was right there in the bunker with him.

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The ICOM IC-R9500 (Know What is Going on Around You in the RF Spectrum)

44-501377-2

What a beautiful piece of equipment!

This is a radio receiver.  Properly set up it will scan from .005 MhZ to 3.335 GhZ.  This tool will give you a clear idea as to what is going on in the electromagnetic spectrum around you.  Scans can be set up, and an external speaker can be attached.  Signals that you recognize can be ignored, and you can look for suspicious signals that pop up.

If you have something around you that is transmitting, something that you did not know about, then this might represent an invasion of your privacy.  A device like this can be used for many purposes.  The one pictured here is extremely sophisticated.  Others are simple and cheap.  The purpose of this device is not to do a technical survey of a room or series of rooms.  It would only be able to find rudimentary listening devices.  Its purpose is to see a big chunk of the spectrum as to what kinds of transmissions are going on in your area.  Although it is true that this receiver would pick up a radio signal coming from your computer if that signal was between .005 MhZ and 3.335 GhZ.  If your computer is sending out a radio signal (with your information) that you do not know about, then it is time to get a new computer.

This receiver will pick up all kinds of traffic:  am radio, HF signals, aircraft, push-to-talk radio, commercial radio, digital signals of many kinds, analog television (audio), encrypted signals (they will only be seen and a garbled noise will be heard), UHF radio, emergency beacons such as avalanche or downed-aircraft locating devices, etc.

psk_matrix2.jpg          PSK-31

The next step is learning about the electromagnetic spectrum and knowing how waves propagate and how they can be modulated.  Learning about the spectrum tells you what kinds of signals are possible at certain frequencies.

Also, one needs to be diligent because some signals only transmit at odd intervals or on unusual frequencies.

One needs to be aware of the legal aspects of using such a device.  Laws vary, of course, by country.  This device is passive, but one must be aware of, and follow, legal restrictions.  Hobbyists use such devices all over the world, but they usually have sections of the spectrum blocked off.  Make sure to follow your local laws.

There are many situations where a scanner like this would greatly enhance the security of a business or organization in hostile parts of the world, especially when this equipment is operated by attentive, competent personnel.  Small scanners can also reveal enlightening information.

Brochure for ICOM IC-R9500

A Table for Trigraph Code Words and Phrases

Blank Code Phrases Table

It is easy to make a table of words and phrases to make communication easier while completely masking the real meaning.  But one has to keep this table safe, and all correspondents will need to have a copy.  There are many ways to use the table.  Sending Vernam Cipher messages is one use.

Storing this table on a computer hooked to the internet defeats the purpose.

TIARA GNOME- An Episode in the History of Cryptography

TIARA GNOME

Below we can see the captured traffic of a momentous message sent from Tokyo to their Embassy in Washington, DC just prior to the attack at Pearl Harbor.  This HF message was captured, but that did little good to prevent the attack.  “OBESE OVALS” stands for the government office in Tokyo that sent the message.

S352/6 1000S GR265
OBESE OVALS TIARA ..OME
62527 ZTXOD NWKCC MAVNZ XYWEE TUQTC IMNVE UVIWB LUAXR RTLVA
RGNTP CNOIU PJLCI VRTPJ KAUHV MUDTH KTXYZ ELQTV WGBUH FAWSH
ULBFB HEXMY HFLOW D-KWH KKNXE BVPYH HGHEK XIOHQ HUHWI KYJYH
PPFEA LNNAK IBOOZ NFRLQ CFLJT TSSDD OIOCV T-ZCK QTSHX TIJCN
WXOKU FNQR- TAOIH WTATW VHOTG CGAKV ANKZA NMUIN
YOYJF SRDKK SEQBW KIOOR JAUWK XQGUW PDUDZ NDRMD HVHYP NIZXB
GICXR MAWMF TIUDB XIENL ONOQV QKYCO TVSHV NZZQP DLMXV NRUUN
QFTCD FECZD FGMXE HHWYO NHYNJ DOVJU NCSUV KKEIW OLKRB UUSOZ
UIGNI SMWUO SBOBL JXERZ JEQYQ MTFTX BJNCM JKVRK OTSOP BOYMK
IRETI NCPSQ JAWVH UFKRM AMXNZ UIFNO PUEMH GLOEJ HZOOK HHEED
NIHXF XFXGP DZBSK AZABY EKYEP NIYSH VKFRF PVCJT PTOYC NEIQB
FEXME RMIZL GDRXZ ORLZF SQYPZ FATZC HUGRN HWDDT AIHYO OCOOD
UZYIW JROOJ UMUIH RBEJF ONAXG NCKAO ARDIH CDZKI XPR– DIMUW
OMHLT JSOUX PFKGE PWJOM TUVKM WRKTA CUPIG AFEDF VRKXF XLFGU
RDETJ IYOLK BHZKX OJDDO VRHMM UQBFO WRODM RMUWN AYKYP ISDLH
ECKIN LJORK WNWXA DAJOL ONOEV MUQDF IDSPE BBPWR OFBOP AZJEU
USBHG IORCS UUQKI IEHPC TJRWS OGLET ZLOUK KEOJO SMKJB WUCDD
CPYUU WCSSK WWVLI UPKYX GKQOK AZTEZ FHGVP JFEWE UBKLI ZLWKK
OBXLE PQPDA TWUSU UPKYR HNWDZ XXGTW DDNSH DCBCJ XAOOE EPUBP
WFRBQ SFXSE ZJJYA ANMG- WLYMG WAQDG IVNOH KOUTI XYFOK NGGBF

Symmetric Warfare: Using Code Words to Send Unobservable Messages

Using code words in a normal-looking message is a cheap and effective way to communicate. 


Scenario:

Several American businessmen are in Kuala Lumpur, Malaysia trying to get a contract signed for a lucrative mining deal. Mike, the head negotiator, communicates with his iPhone over a 3G GSM network, and he uses his corporate e-mail account via his laptop.

Before he left home he came up with a series of code words to use when he communicates with his boss. This simple and cheap method defeats and misleads national-level eavesdropping, hackers, competitors who eavesdrop, and everyone else who wants to spy on him. Just keep your special word list safe. Beware of thinking that old school is somehow wrong, or that it offers flimsy security. The opposite is true. Flying under the radar is a very good idea these days, and simple is good.  He printed his little code word table on a piece of paper and he hid that paper inside his wallet.

Here is the code word list for the above scenario:

SPECIAL WORD(s)                                           MEANING

NORTH                                          THE BUSINESS DEAL DID NOT GO THROUGH

SOUTH                                          THE BUSINESS DEAL DID GO THROUGH

EAST                                             THINGS LOOK PROMISING BUT NOT YET COMPLETE

WEST                                             HUGE SUCCESS

NORTHEAST                                 UTTER FAILURE

NORTHWEST                                 WE NEED MORE TIME

NICE PLACE                                   WE ARE BEING WATCHED

GOOD RESTAURANT                    PROBABLY WE ARE NOT WATCHED

CHINESE                                        THEY SIGNED THE CONTRACT SECRETLY WITH US

JAPANESE                                      THEY REFUSED TO SIGN THE CONTRACT

INDIAN                                            THEY SIGNED THE CONTRACT WITH US OPENLY

THAI                                                THEY ARE NOT CORRUPT

WRITE YOU TOMORROW             OTHERS ARE OFFERING PERKS

CALL YOU TOMORROW                WE HAD TO OFFER SOME PERKS

One can then write a misleading message containing special words with special meanings.   So here is the letter Mike writes:

John,

I am very sorry to say that the deal did not go through. We are extremely disappointed by the behavior of their people. Tonight we are going to take a break after all these days of hard work. We are going to that Chinese restaurant west of here that you said is a nice place. Call you tomorrow.

Mike


Come up with traffic that sounds reasonable given the realities of the context. In the scenario above one could expect that a Chinese, Thai, Japanese, or Indian restaurant really does exist west of the speaker’s location. Tell everyone else involved in the business transaction to stay mum over the deal, and tell them to be especially careful over the phone or on the internet. Best practice would be to assure that as few people know about it as possible. Only those who need to know should be told about it.

The message and code word table above is for a specific purpose.  A longer table can be the basis for extended conversations on varying subjects.  Keeping the code word table secret is a priority.  One can write it down, one can print it at home on a small piece of paper, or one could encrypt it with a 4096 bit PGP key and use it on a computer that is never attached to the internet.  This last course of action is the least recommended.

And yes, if the situation is that bad, find a Chinese restaurant west of you and have dinner after you send your fake message.

The point of all this is that simple human means can defeat elaborate mechanical threats.  It does not take high technology to defeat the masters of high technology.  It simply takes a little thoughtful effort.

Symmetric Warfare

Simple Means Can Succeed Against Incredibly Sophisticated Technology

Symmetric systems can sometimes offer unobservability. Sending hidden messages in routine traffic is always going to be possible. Imitating the whole system of routine traffic does not work because the task is too complex for the imitator. For example, a nearly perfect imitation of Skype can be detected very easily. Do not trust providers who promise you security based on the notion that their system fully imitates another system without being subject to attack.  It is better to send an encrypted message via a normal high-volume traffic route, like Skype, instead of using a service that tries to imitate a whole system with its immense complexities. Also, Skype is easy to use. Yahoo! is easy to use too.


Read the following message and try to guess if it holds hidden information:

Dear John and Teresa,
      How are you? I hope everything is going well.  Thanks for having us over! It was really nice to see you. Wow! That was the best barbecued chicken ever. An amazing dinner! I hope we can come back in October. Right now my work is a real headache. Fran is busy too. The kids keep our hands full. Especially Tommy. I hope the kids were not too much problem at dinner. And I am sorry Tommy broke that vase.
      Fran just got a new one. Please accept it. OK? She is going to bring it over next week. Please don’t worry. She is going to be in town for two days next week because of a conference, and it is easy for her to stop by. So give us a call this week if you can.
      Again, it was so fun to see you two again and I am really sorry about the vase. Hope to see you soon myself when work slows down. Things have been hectic. You can imagine. I have to work late just about every night. No time to do anything except get some sleep and show up back at work.
      Gotta run! Take care and see you both soon.

Adolf

There is a plaintext message inside the letter. Count the number of words in each sentence (after the greeting).

36571738846218631935080439527 (Plaintext)
In this system a sentence with 13 words resolves to a three. Ten words resolves to a 0.
Using a code pad somewhat similar to the STASI “TAPIR” the plaintext resolves to the following message:
MINEOWNERWANTSBRIBE
Mine owner wants bribe

So this message was sent in the clear (in plaintext).  That is not the best lifestyle decision.  Someone clever could guess you are communicating this way, and he could go to work to resolve your message by guessing the format of the code pad.  In fact, come to think of it, such an effort could be automated.  Simple code pads would be the most vulnerable.  But there is a solution.

The best way to send this message is to not send plaintext.  Send ciphertext.


Send an unobserved and unbreakable message with a random symmetric key

Gestapo 2.0 has arrived to your world, and you want to foil them.

1.  Decide on your message.

Message:        Go to the synagogue

2.  Use a code pad like the one below:

Gnome Code Pad 2

3.  Convert your message into numbers using the code pad.

65378378667557106536541

4.  Use a one-time-pad key designated by the greeting:

“Hey!”

“Hey!” equals key:

15423 89479 30985 95704 35770 95893 07814 10585 98524 24782 94553 89265 84302 52941

Both you and your correspondent have this key prior to the message being sent.  So you want to hide your one-time-pad keys.  You have to be careful that the Gestapo does not find your keys, but the huge advantage is that your message is not subject to computational attack.  They can look at it forever with a planet full of computers, but this will do no good at all.

5.   Add the plaintext to the key without carrying over.

Here is your ciphertext:

70791 16235 05456 91230 898

6.  Write your letter (Each sentence will have the number of words as in the ciphertext. Seven words, then 10 or 20, seven again, etc.  Contractions count as one word):

Hey!

My trip to Berlin was really fun.  The people there are so sophisticated and friendly and relaxed.  I walked around downtown all day long.  I have to tell you that it is beautiful.  Really!

Gosh.  Berlin has so many good restaurants.  Cheap too.  It was fun.  I want to go back.  One thing that stood out to me was how clean everything was, not just the restaurants, but the streets too. It is a vibrant city. I just love it. Maybe we can go together? I really enjoy the cosmopolitan atmosphere.

How have you been doing with your new studies?  Ok?  How’s Ben?  He’s so funny.  I hope that he can help you with your school.  I know he is a bright, diligent student.  Why not ask him again to help you out?

Maybe I’ll see you in a couple weeks!

Arthur


So you see that this method takes some time to create the story, to encrypt the message hidden in the story, and then to decrypt it.  Using a code table might be faster and easier for some messages.  Also, one can come up with one’s own methods based on the idea of hiding ciphertext in a normal-looking letter.  Both you and your correspondent need to have the prearranged set of keys, and the code pad.

One of the lessons here is that low-tech means can achieve high-end results.  If both correspondents destroy their key to this message after it is used, destroy it completely, then that is another plus.