RunRyder RC
 1  Topic Subscribe
WATCH
 1 page 591 views POST REPLY
HomeOff Topics › Crack the code...
12-12-2004 11:44 PM  13 years agoPost 1
rchelipilot121

rrNovice

Crap!! I'm here again!!

My Posts: All  Forum  Topic

One of the methods used to encrypt a message is to use the message itself. We begin by providing a secret number that is used for the offset of the first letter and is known only to sender and receiver. This starting value is called a seed. For example, if we encode the word, CAT, we begin by finding the alphabetic value of each letter: 3, 1 and 20; and then use the value of the previous letter as an offset, with the first letter using the seed value.

Suppose the seed is 5:

C (3) ® (3 + 5[seed] = 8) H
A (1) ® (1 + 3[1st letter] = 4) D
T (20) ® (20 + 1[2nd letter] = 21) U

So the encoded message is HDU. It should be clear how, using the seed 5, it is possible to decode it easily.

However, your task is to decode the following message without being told the seed:

X B M W W N B G C U A O O M W N W H C V R Y L S W A Q

Good luck!

PM  EMAIL  Attn:RR  Quote
12-13-2004 05:00 AM  13 years agoPost 2
heliham

rrApprentice

San Jose, CA

My Posts: All  Forum  Topic

I need another rule.

If the message were CATT with a seed of 5
it would encode as:

C (3) ® (3 + 5[seed] = 8) H
A (1) ® (1 + 3[1st letter] = 4) D
T (20) ® (20 + 1[2nd letter] = 21) U
T (20) ® (20 + 20[3rd letter]= 40) ?? maybe N (mod 40,26)

but that gives me a problem when I try to reverse the operation. I can get a ZERO which doesn't equate to any letter. I need the rule for modulo arithmetic and what to do for a ZERO.

Regards,
...paul

PM  EMAIL  GALLERY  Attn:RR  Quote
12-13-2004 05:38 AM  13 years agoPost 3
heliham

rrApprentice

San Jose, CA

My Posts: All  Forum  Topic

NEVER MIND...
I figured out what the rule had to be.

There is no future in time travel.

Regards,
...paul

PM  EMAIL  GALLERY  Attn:RR  Quote
12-13-2004 05:58 AM  13 years agoPost 4
rchelipilot121

rrNovice

Crap!! I'm here again!!

My Posts: All  Forum  Topic

C (3) ® (3 + 5[seed] = 8) H
A (1) ® (1 + 3[1st letter] = 4) D
T (20) ® (20 + 1[2nd letter] = 21) U
T (20) ® (20 + 20[3rd letter]= 40) ?? maybe N (mod 40,26)
...............................................= 14) N

You will never have a zero, or a number higher than 26. The alphabet wraps around.

Hope this helps.

PM  EMAIL  Attn:RR  Quote
12-13-2004 12:16 PM  13 years agoPost 5
Drunk Monk

rrProfessor

Preston, UK

My Posts: All  Forum  Topic

The seed is 4

There is no future in time travel


Wehey, I did 2 now


Stephen

I only open my mouth to change feet.....

PM  EMAIL  GALLERY  Attn:RR  Quote
12-13-2004 09:41 PM  13 years agoPost 6
rchelipilot121

rrNovice

Crap!! I'm here again!!

My Posts: All  Forum  Topic

I don't know what you guys are talking about, that's not the answer......


Just kidding. Way to go!

PM  EMAIL  Attn:RR  Quote
12-13-2004 09:46 PM  13 years agoPost 7
Drunk Monk

rrProfessor

Preston, UK

My Posts: All  Forum  Topic

lol


Stephen

I only open my mouth to change feet.....

PM  EMAIL  GALLERY  Attn:RR  Quote
12-13-2004 09:59 PM  13 years agoPost 8
heliham

rrApprentice

San Jose, CA

My Posts: All  Forum  Topic

Your next challenge is to find a text string that can be encoded like that and which will giveTWO (or more) different outputs depending on what seed you use.
...paul

PM  EMAIL  GALLERY  Attn:RR  Quote
WATCH
 1 page 591 views POST REPLY
HomeOff Topics › Crack the code...
 Print TOPIC  Make Suggestion 

 1  Topic Subscribe

Wednesday, June 20 - 4:26 am - Copyright © 2000-2018 RunRyder   EMAILEnable Cookies

Login Here
 New Subscriptions 
 Buddies Online