Traditional ciphers are cryptographic techniques used historically to secure messages. They rely on simple mathematical or letter-based manipulations rather than complex algorithms like modern encryption. These ciphers are generally categorized into:
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Substitution ciphers – replace elements of the plaintext with ciphertext (e.g., letters replaced with other letters).
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Transposition ciphers – rearrange the order of characters in the plaintext without changing the actual characters.
1. Substitution Cipher Example: Caesar Cipher
Definition:
In a Caesar cipher, each letter in the plaintext is shifted a fixed number of places down the alphabet.
Example (Shift = 3):
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Plaintext:
HELLO -
Ciphertext:
KHOOR -
H → K
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E → H
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L → O
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L → O
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O → R
Merits:
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Simple to implement and understand.
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Requires minimal computational resources.
Demerits:
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Easily broken using frequency analysis or brute-force (only 25 possible shifts).
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Not secure for modern communication.
2. Transposition Cipher Example: Rail Fence Cipher
Definition:
The letters of the plaintext are written in a zig-zag pattern (rails) and then read row-wise to form the ciphertext.
Example (Depth = 3):
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Plaintext:
WEAREDISCOVERED -
Zigzag writing:
W . . . R . . . D . . .
. E . E . D . C . V . R
. . A . . . I . . . E .
- Ciphertext:
WRDEEDCVREAIE
Merits:
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Preserves letter frequency, making frequency analysis harder.
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Adds confusion by changing the order of letters.
Demerits:
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Still vulnerable to pattern detection.
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Requires knowledge of the transposition key (e.g., number of rails).