An Unbreakable Code - Old School

Topics on Radio (CB, GMRS, Ham, etc), GPS, Smoke Signals, or whatever else you can use to talk to other people who are not within yelling distance.

Moderator: ZS Global Moderators

User avatar
Leckie
* *
Posts: 191
Joined: Tue Jan 22, 2013 2:18 pm
Favorite Zombie Movies: Shaun of the Dead
Location: Hamar, Norway

Re: An Unbreakable Code - Old School

Post by Leckie » Tue Jan 22, 2013 7:09 pm

Ouh, nice one!

However, this is my favorite


2 5 0 8 9 1 3 4 6 7 (if you don't get it, you take your numbers write then down and continue the sequence from one to zero, neglecting the numbers you picked)
1 2 3 4 5 6 7 8 9 0

Combine with a specific book (page, line, word) and then it would look something like this:

13-0-9 Translated "67-3-5"
0-8-3 Translated "3-4-7"

(example, made up book)
67-3-5 Translated "hello"
3-4-7 Translated "guys"



And you have a fairly unbreakable code.. you also need 2 people(preferably) to decode it! Minimizes the risk of exposure if one of the decoders is blackmailed/compromized

Or this one with letters

C I P H E R A B D F G J K L M N O Q S T U V W X Y Z

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Life is about learning; when you stop learning, you die.
- Tom Clancy

My topics:
Mylar bags FAQ and tips
Winter Survival 101
My BOB

User avatar
Sins
* * *
Posts: 572
Joined: Sun Jul 22, 2012 3:58 pm

Re: An Unbreakable Code - Old School

Post by Sins » Tue Jan 22, 2013 7:36 pm

AZiqz bpz cenuxjgu

^that is an unbreakable code I developed for some friends. If anyone wants the code p.m. Me.
Give it a week though. I want to see if anyone can break it. So far nobody has, even though it's simple

If anyone here can break it they are pure genius.
What I did say was a compliment to the thread if you need a hint

User avatar
crypto
ZS Donor
ZS Donor
Posts: 16637
Joined: Sun Oct 08, 2006 7:37 pm
Location: City of Saint Louis

Re: An Unbreakable Code - Old School

Post by crypto » Tue Jan 22, 2013 8:02 pm

Thats a very small ciphertext sample to try to analyze for an attack, to be honest.
MF'N TEAM LEADER

"Some people think that the best way to stop the leopard is to cut the horns off the gazelle. This, my friends, is insane."

Image
Image

User avatar
Sins
* * *
Posts: 572
Joined: Sun Jul 22, 2012 3:58 pm

Re: An Unbreakable Code - Old School

Post by Sins » Tue Jan 22, 2013 8:36 pm

crypto wrote:Thats a very small ciphertext sample to try to analyze for an attack, to be honest.
Alright I will type something up longer.
Also the capitalization of letters doesn't matter just to be fair its how my phone typed it with the "AZ"

azit bicgz ca dkmj etco fy glxnniabd hi imiuifs jpqcw kabf ls mtwrxmlkxjbh nftmy. ov puzhqqf qdjrp rk snruxe txfd ue vommq wha xesmbh yds zmssf.

User avatar
GoSlash27
* * * * *
Posts: 1906
Joined: Wed Apr 26, 2006 4:59 am
Location: Iowegia
Contact:

Re: An Unbreakable Code - Old School

Post by GoSlash27 » Sun Feb 03, 2013 11:16 am

One- time pads are completely invulnerable to brute force cracking, but they are also cumbersome.
If you just want to create a quick and easy cipher that will stand up long enough that by the time it gets deciphered it won't matter, there's an easier way.

It's called keyword transposition with monoalphabetic substitution. So let's say that you and the intended recipient have agreed upon "ZOMBIE" as the keyword, and the message reads "TGT ALPHA SOUTH WALL UNGUARDED ATTACK THURS MORN".

The sender would first attach a new keyword to the end of the message. In this case, say "GERONIMO"*

The message is first placed in a matrix below the keyword

ZOMBIE
_________
TGTALP
HASOUT
HWALLU
NGUARD
EDATTA
CKTHUR
SMORNG
ERONIM
O

Fill in the remaining spaces with a common letter that does not appear in your keyword.

ZOMBIE
_________
TGTALP
HASOUT
HWALLU
NGUARD
EDATTA
CKTHUR
SMORNG
ERONIM
OTTTTT

Next, you number the alphabetical order of the keyword.
ZOMBIE
654132
______
TGTALP
HASOUT
HWALLU
NGUARD
EDATTA
CKTHUR
SMORNG
ERONIM
OTTTTT

Then you Read the columns downwards in the order of the number above it.
AOLATHRNTPTUDARGMTLULRTUNITTSAUATOOTGAWGDKMRTTHHNECSEO

This scrambling makes it impossible to crack the code by looking for word patterns.

Next, you do an alphabetic substitution as described above
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Z O M B I E A C D FG H J K L N P Q R S T U V W X Y

AOLATHRNTPTUDARGMTLULRTUNITTSAUATOOTGAWGDKMRTTHHNECSEO
ZLHZSCQKSNSTBZQAJSHTHQSTKDSSRZAZSLLSAZVABGJQSSCCKIMRIL

This substitution safeguards the code from frequency analysis. Decryption on the other end is the reverse, with the added step that the recipient must count the number of characters in order to know how many rows to put in the decode matrix.
In this case 45 characters in the message divided by 6 letters in the code word means that there are 9 rows.

The reply message would be encoded by the keyword "GERONIMO"* and contain a new keyword, such as "AVALON"*. The beauty of this system is that even if the code is compromised, it only decodes the one message. To stay in the loop, it requires intercepting both sides of the conversation.

This system is sufficiently secure that our own military used it regularly throughout the cold war. It is believed that the Zodiac killer used a variant of this for his Z340 message, and it remains uncracked to this day.

* Note When using keywords with repeating letters, the alphabetical order for the matrix is the order that the letter appears in the word. Ex. "AVALON" would be 162354. When decoding messages, you omit excess characters from the end of the cryptogram alphabet and the doubled character has a doubled meaning. For an AVALON alphabet, "A" in the encrypted message could mean A or C, and the letter Z will not appear.
Image
R.A.S.P!
.. ... . . .,, .... ., , ,.,, ,,, .., ,.. .. ,.. , .... . .,. . ,,..,, ,.,. .,. ,.,, .,,. , ,,, .,.,.,

00dlez
ZS Member
ZS Member
Posts: 471
Joined: Mon Jan 14, 2013 3:20 pm

Re: An Unbreakable Code - Old School

Post by 00dlez » Fri Mar 01, 2013 11:41 am

neat post

If anyone was wanting some practice - decipher this:
Key - 54984
69250 61377 09252 63339 69531 71277

(Hope I didn't make any errors.... :oops: )

Edit: I thought about my previous question and answered it myself :)
Batman has a pretty good EDC. - Purple_Mutant

User avatar
Spookadelic
* *
Posts: 102
Joined: Thu Sep 16, 2010 8:47 am
Location: Central Illinois

Re: An Unbreakable Code - Old School

Post by Spookadelic » Wed Feb 12, 2014 7:31 pm

Hope I don't get into trouble for necromancy....

An easier one time pad.

An easier way to use a one time pad is to randomly generate a lot of characters you would normally use for your messages.
Such as this:
W I L A Y B T Q G J E
and use it to encrypt this:
S P O O K A D E L I C
using a tabula recta http://en.wikipedia.org/wiki/Tabula_recta
To generate the following cipher text:
O X Z O I B W U R R G

this method gets rid of the lengthy nuisance of the arithmetic of the other methods.

About randomness
normal random number generator on a computer is fine for most general uses of short messages.
however if you want to be very secure you need to use a Cryptographically Secure Pseudo Random Number Generator.
http://en.wikipedia.org/wiki/Cryptograp ... _generator

Why is a one time pad so secure?

Because you can make it say anything with the right key.
For example using the cipher text above and the following key:
K T Z H B B Y E E F C
you get the plain text below.
W E A T T A C K N O W
so brute forcing a one time pad looking for words is pointless.

Post Reply

Return to “Communications”