diff --git a/study-log.md b/study-log.md
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--- a/study-log.md
+++ b/study-log.md
@@ -21,6 +21,20 @@ Questions:
 
 **Log** (newest first)
 
+**2026-03-20**
+- Lecture 1 — Intro to Cryptography (skimmed notes, pages 2–15)
+
+Notes:
+- Base and recursive construction of natural numbers — the "stepper function" (forgot exact term)
+
+Questions:
+- Most of the content is still unclear. Rather than forcing comprehension, treating this as a "gap survey" — noting what foundational topics I need before this clicks: groups, fields, modular arithmetic, cyclic structures.
+
+Comment:
+- Smart approach. Skim + attend lecture + log gaps = right strategy at this level. Don't fight it — just map the territory.
+
+---
+
 **2026-03-19**
 - Khan Academy: Sets & Their Representations (110 minutes) — https://www.khanacademy.org/math/ka-math-class-11/x0419e5b3b578592a:sets-ncert-new/x0419e5b3b578592a:sets-and-their-representations/v/what-are-sets