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Lesson 6
XENOCRYPT
Aristocrat in Spanish — foreign letter frequencies
What is a Xenocrypt?
- A monoalphabetic substitution cipher — just like Aristocrat
- Key difference: the plaintext is in Spanish (in Science Olympiad)
- Word spaces are preserved (like Aristocrat, not Patristocrat)
- Appears as DC at all levels — can be Decrypt or Cryptanalysis
- The test will indicate it's a Xenocrypt
Why Spanish Matters
- Spanish has different letter frequencies than English
- Spanish top letters: E A O S R N I D L C T U M P
- Most common word: DE, LA, EL, EN, LOS
- Common endings: -CIÓN, -MENTE, -ANDO, -IENDO
- Letters Q, K, W, X are very rare in Spanish
If the test says Xenocrypt — switch to Spanish frequency tables immediately.
Spanish Frequency Table
| Rank | Letter | Freq % | Rank | Letter | Freq % |
|---|
| 1 | E | 13.7 | 6 | N | 6.7 |
| 2 | A | 11.5 | 7 | I | 6.3 |
| 3 | O | 8.7 | 8 | D | 5.9 |
| 4 | S | 7.9 | 9 | L | 5.0 |
| 5 | R | 6.9 | 10 | C | 4.6 |
- E is still #1 but A and O are much higher than in English
Useful Spanish Words to Know
- DE — of / from
- LA / LAS — the (fem.)
- EL / LOS — the (masc.)
- EN — in
- QUE — that / which
- UNA / UN — a / an
- ES — is
- SE — reflexive particle
- CON — with
- POR — for / by
- NO — no / not
- SU — his / her / their
Worked Example
Ciphertext
QT WMBQF MTH JMHQF XW QHDMSQWBAR
- 2-letter word QT — try EL, LA, DE, EN
- Repeated Q in QT and WMBQF and JMHQF → Q is probably E
- With Q=E: QT = E? → try EL, ES, EN
- T=L → check XW → fill in and iterate
Strategy Summary
- Confirm it's Spanish (test label says Xenocrypt)
- Count cipher letter frequencies → map to E A O S R N …
- Find 1-letter words: only A or Y in Spanish
- Find 2-letter words: DE, LA, EL, EN, ES, UN, NO
- Use common endings: -CIÓN, -ANDO, -MENTE
The test always provides a Spanish frequency guide — use it!
Key Takeaways
- Xenocrypt = Aristocrat with Spanish plaintext
- Use Spanish letter frequencies (E A O S R N …), not English
- Learn 10–15 common Spanish words for pattern matching
- Appears as DC at all levels
- Next class: Fractionated Morse — Morse code + substitution
Homework: memorize the top 10 Spanish letter frequencies and 10 common 2-letter Spanish words.