How to Decrypt Message in Covert Action

A quick explanation and some tips on solve the decryption mini-game

How Decryption Mini-Game Works

In Covert Action, one of the mini-games you need to play is decryption, where you intercepted a message between two enemy agents and you need to decrypt it to figure out what they said, which will give you a ton of information.

In CA, the codes are relatively simple substitution cipher, which basically means one letter was substituted for another letter through some sort of a table or formula. To be accurate this is called simple substitution monoalphabetic cipher where each letter only stands for one other letter.

The difficult level (there are 4) are as follows:

Local Disturbance (i.e. easy): not only you get all the spaces and punctuations, you also get one free letter solved for you. (it's as if you get one free press of the F1 hint)

National Threat (i.e. Medium): no more free letter, but still the punctuations and spaces

Regional Conflict (i.e. Hard): all punctuations have been removed

Global Crisis (i.e. Elite): no spaces, just punctuations

For illustration purposes, I'll use the easiest difficult level, but the principle to solve them is the same.

Decrypting the Message

How Messages are Generated

Message generally follow some common templates and as you play this game you will recognize the templates more and more as you see the same phrases over and over, only the city names and organization names change.

There's a list of such phrases at the end of the guide. Obviously this is not a comprehensive list, but it should give you some ideas.


Things you need to remember or memorize BEFORE you start decryption:
1) Have a list of ALL the city names in the game. Yes, ALL of them. Print it out in big letters and have it next to you. You will be referring to it.

2) Have a list of ALL the organization names in the game, exactly as the game spelled them. You will be referring to this as well.

3) The most common letter in English ie E, followed by R S T L N

4) on a sticky note or such, note the suspected organization(s) involved in the message, as well as the city sent from or to, if you know them.


Solving the Encryption

First thing you need to start is assume the letter with the highest count is E, enter that.

Then look for the city name or organization name or city name with E in it and look for patterns that can fit in the message. Those are often quite long and can give you a LOT of letters solved. You can search for the shorter words like ARE or THE but those don't help much.

If none seem to fit, pick the next two most frequent letters and try them with S and T (or T and S if that doesn't seem to work). Again, try to fit organization or city names.



When to Use a Hint (and lose 1 hour of game time)

The game runs at an accelerated time, but most puzzles can be solved, at least on easy, in less than 10 minutes gametime (2-3 minutes real-time). However, if you fail to make much progress by game timer of 20-30 minutes, it may be time to sacrifice 1 hour of gametime for a hint (i.e. have the computer solve a letter for you). However, remember, if you are thoroughly lost, you can hit F10 to reset the board (which erases all YOUR guesses, but not the computer solved letters).


Hints for solving higher-difficult levels
As you no longer get spaces figuring out where word begins and ends becomes extra difficult. Thus, it becomes even more necessary to remember at least SOME of the phrases (check the end) so you can insert them when noted. Keep in mind that some of those phrases do occur near the beginning of sentences, and thus can be exploited. For example, if the second letter is E, there's a good chance first letter is W. Note the patterns, not just words.


Practice, practice, practice

You can do the practice sessions on whatever difficulty level you want. The catch is the messages are randomly generated therefore there is no contextual clue (i.e. which cities or organizations are involved) which makes things much harder.

Examples of Decryption, all difficulty levels

Some of the more common phrases

Some of the other common phrases that pop up quite often includes (in no particular order):

DEDICATED BRETHREN
WE SALUTE YOU
WE WELCOME COOPERATION
WE ARE CONFIDENT
YOUR SUCCESS ASSURES
VICTORY TO OUR COLLEAGUES
ALL TRUE COMRADES
ADMIRE YOUR WORK
COMMEND YOU FOR EXCELLENT WORK
DEVIATIONS FROM THIS PLAN ARE NOT ACCEPTABLE
REQUIRES TOTAL COOPERATION
REMEMBER WHO YOU ARE DEALING WITH HERE
ENEMY ACTIVITY
THIS OPERATION HAS THE APPROVAL OF
HIGH COMMAND
THOSE WHO SERVE
SOME ASPECTS OF THE SITUATION REMAIN UNCLEAR
ARE WELL REWARDED
ECHOES WITH PRAISE OF YOUR SUCCESSES
COMRADES
FELLOW WARRIORS
NOW IS THE TIME FOR ACTION
TIME IS OF THE ESSENCE
READY TO REWARD YOU FOR YOUR SUCCESS
OUR CAUSE CANNOT FAIL
WONDERFUL TIME
OUR SYMPATHIZERS CAN BE FOUND EVERYWHERE
WISH YOU WERE HERE
CURRENT SITUATION
HAS BEEN MODERATE
THANKS FOR YOUR ASSISTANCE
YOUR EFFORTS ARE NOTED
WE NOTE THE HEROIC ACTION
TAKE PRECAUTIONS
OUR POWER INCREASES WITH EACH PASSING DAY
PROCEEDING ON SCHEDULE
WE WELCOME COOPERATION WITH

Obviously this is not a comprehensive list, but you should recognize them when you see them.

[Virtue Power]

List of cities:

BOGOTA
WASHINGTON
CARACAS
HAVANA
KINGSTON
LONDON
LOS ANGELES
MANAGUA
MEDELLIN
MEXICO CITY
MIAMI
NASSAV
PANAMA
RIO
SAN JUAN
TEL AVIV

[kschang77]

From what I can tell, it acts as a "modifier" toward the respective minigame. A Crypto skill point makes your crypto 1 level "easier". Similar for other minigames. So if you have 4 points, and apply it all to crypto, all your OTHER minigames will get harder, but crypto becomes every easy even as hardest threat level. But that's mainly a guess.

[Webmonkey]

How does the crypto skills during character creation affect this puzzle??

[KMickle]

Not polyalphabetic, but homophonic (it might as well be near-trivial polyalphabetic). The shorter the message, the higher the probability of getting an unbijective link. My observations show that most ciphertexts have 1 plaintext letter with two images. I also briefly recall seeing 2 letters with two images. It seems, that the game tends to "split" letters with higher probabilities (the last example I remember was with ~29 'E' split into two ciphertext letters with 14~15 entries each), but this might have been a coincidence.

I haven't played much on max difficulty, though.

[kschang77]

I dont' recall seeing polyalphabetic ciphers at higher difficult levels. I'll double check.

[KMickle]

My experience says, that variation rows (letter frequencies) are totally ineffective. The reasons are (1) tme message is way too short and, most importantly, the cipher is not a classic substitution cipher — some letter of the plaintext may have two different representations in the cipher. The 'E' letter is often "split" in such way; so, plaintext 'E' may be represtented by ciphertext 'A' and 'B'. So a word **EE* may look like **AB* or **AA* or **BA* or whatever. In most cases the cipher has 1 such letter and it is often 'E'.

What you CAN use:
1. Get as much info as possible about the message: sender and recepient organizations, source city and destination city. These words are extermely likely to be in the message;
2. If there are spaces in the message, pay attention to 2~3 letter words. **AA may stay for WILL; ABC & DBC may represent WAS and HAS. Along with city guesses, that is often enough.

[KMickle]

3. If there is a word with one letter, it is 'A'.
4. Whenever anything else fails, identify letter repeat patterns. Example: Stassi = A**AA*; THE HEROIC = *ABAB****; and so on — make observations as you play on easier levels (start with cities and organization names);
5. If even 4 is of no use, take F1 hints. You may have to take several, if you have had bad luck. After you get a hint, repeat repetition analysis and 2-3 letter word analysis.

On difficulty levels with spaces, steps 3 --> 1 --> 2 typically yield a solution quickly.