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Succinct Start Schedule (Posted on 2009-01-19) Difficulty: 2 of 5
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.

Decode this 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

See The Solution Submitted by K Sengupta    
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Hints/Tips If only... | Comment 1 of 4
If only I could visit the future and look at the posted answer and bring it back here to the present, and post it myself.
  Posted by Charlie on 2009-01-19 12:32:58
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