The document discusses the rail fence cipher technique for encryption and decryption of text. It explains that the rail fence cipher arranges the characters of a plaintext message in a diagonal pattern, alternating between moving down and up in rows. It also uses two counters, one starting at the beginning and looping once, and the other starting after the first and looping to the end, to encrypt the message by reading down the columns.

1. What is this line doing?
What are the two 26s for?

2. This is where we use the ApplyShifttoASCIICodeForCharacter function
To get the encrypted text.
How do we decrypt?

3. The “rail fence”
T t a Jh i h r M oi s e m r ns y e s
Size = 4

4. The “rail fence”
T t a Jh i h r M oi s e m r ns y e s
Size = 4

5. The “rail fence”
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Size = 4

6. The “rail fence”
T t a J
h i h r M o
i s e m r n
s y e
s
Size = 4

7. How the algorithm works
2 Counters
T t a Jh i h r M oi s e m r ns y e s
Counter one starts at the beginning and loops once only
Counter two starts at counter one and loops to the end

8. T t a Jh i h r M oi s e m r ns y e s

9. T t a J
h i h r M oi s e m r ns y e
s
For Count1 = 1 To SizeOfRailFence
While Count2 < OriginalText.Length
Count2 = Count2 + SizeOfRailFence