Rot13
ROT13 is a substitution cipher that rotates each letter of the Latin alphabet thirteen positions, making encryption and decryption identical.
Functional Programming in JavaScript
A simple substitution cipher that rotates alphabetic characters by 13 positions.
- How it is used
- Demonstrates memoization on a referentially transparent function with the same input-output result.
- How deep it goes
- Defines ROT13 briefly and stops short of the full cipher details, using it mainly as a performance example.
- Examples
- Uses a discount-code string and repeated calls to show encoded output and cache reuse.
- What you can do after
- Apply it via memoization and get faster repeated calls from cached results.
Read how Functional Programming in JavaScript explains rot13 →
Natural Language Processing in Action, Second Edition
A Caesar cipher is a substitution cipher that shifts each letter by a fixed position in an ordered alphabet.
- How it is used
- Uses ROT13 to recognize and decode an encoded secret message through letter shifts, frequency patterns, or Python utilities.
- How deep it goes
- Demonstrates the cipher’s intuition, frequency-based shift discovery, character-level implementation, and library-based decoding.
- Examples
- Uses the encoded Zen of Python, character-count tables, frequency histograms, and Python decoding commands.
- What you can do after
- Apply it via Python’s codecs package to decode ROT13 messages.
Read how Natural Language Processing in Action, Second Edition explains rot13 →
Learn Haskell by Example
ROT13 is a Caesar cipher that rotates letters by 13 positions in the basic Latin alphabet, making the same transformation serve as encryption and decryption.
- How it is used
- Uses reversible letter scrambling to introduce Caesar ciphers, character transformations, and Haskell's `map`.
- How deep it goes
- Explains the symmetry, implementation structure, digit handling, and frequency-analysis weakness, but stops short of secure cryptography.
- Examples
- Demonstrates ROT13 text scrambling, a letter-substitution wheel, and reversible ROT13-plus-ROT5 digit encoding.
- What you can do after
- Build it from scratch in Haskell using a parameterized Caesar function and `map`, then test reversibility.
Related concepts
- Caesar cipherkind of · A Caesar cipher is a substitution cipher that shifts each alphabetic letter by a fixed number of positions with wrap-around.
- encryptionuses · Encryption is the cryptographic transformation of readable data into ciphertext to conceal its contents, reversible through decryption with appropriate information.
- property-based testingused by · Property-based testing is a software-testing technique that generates varied inputs and checks whether specified general properties of the software’s behavior hold across them.
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