135cf1ff01
- Expand instructions.md with step-by-step manual encryption/decryption example using modular addition. - Add padgen.py script to generate random one-time pads from /dev/urandom, formatted in groups. - Add cleanup of temporary audio file in numbers_station.sh. - Minor title update in site/index.html for clarity.
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HOW TO DECRYPT — STEP BY STEP (by hand)
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Key Generation
- You generate a truly random key that is exactly as long as the plaintext message.
- The key must be purely random (each bit or character has equal probability and no patterns).
- The key is shared securely between sender and receiver in advance (this is the hard part in practice).
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Encryption
- Take the plaintext message.
- Combine it with the key using a reversible operation. The two most common methods are:
- Bitwise XOR (for binary data — the standard modern way)
- Modular addition (for letters, e.g., A=0, B=1, ..., Z=25 — the classic "pad" method)
Example with letters (Vigenère-style addition mod 26):
Plaintext:
H E L L O
→ Numbers:7 4 11 11 14One-time pad:
X M C K L
→ Numbers:23 12 2 10 11Ciphertext:
(7+23) (4+12) (11+2) (11+10) (14+11) mod 26
→4 16 13 21 25
→ Letters:E Q N V Z -
Decryption
- The receiver does the inverse operation with the same key.
- For modular addition: subtract the key (mod 26).
- For XOR: XOR the ciphertext with the key again (XOR is its own inverse).
Ciphertext:
E Q N V Z
Key:X M C K L
Plaintext:H E L L O
HOW TO DECRYPT — STEP BY STEP (using your 8-bit machine)
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Type in the NERDLETTER DECRYPTOR BASIC program (provided with your subscription)
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RUN
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When it asks, type the PAD groups from the appropriate page:
VLGKUthenJXCYHthenLYMDCthenETLUB -
Then type the CIPHERTEXT groups:
HLXIBthenJACJPthenERXHNthenEFM -
The machine will instantly print the plaintext!
RESULT YOU SHOULD SEE:
MARYHADALITTLELAMB
(Add spaces by hand: “Mary had a little lamb”)
This is perfect secrecy — no computer on Earth can read it without this exact Day Book page.