diff --git a/second-edition/dictionary.txt b/second-edition/dictionary.txt
index 6147d8f7b2..1abbb31604 100644
--- a/second-edition/dictionary.txt
+++ b/second-edition/dictionary.txt
@@ -75,6 +75,7 @@ CPUs
 cratesio
 CRLF
 cryptocurrencies
+cryptographic
 cryptographically
 CStr
 CString
@@ -227,6 +228,7 @@ libreoffice
 libstd
 lifecycle
 LimitTracker
+LLVM
 lobally
 locators
 LockResult
@@ -272,6 +274,7 @@ namespace
 namespaced
 namespaces
 namespacing
+natively
 newfound
 NewJob
 NewsArticle
diff --git a/second-edition/src/appendix-06-newest-features.md b/second-edition/src/appendix-06-newest-features.md
index 3f2e1ac3ae..841eb5a436 100644
--- a/second-edition/src/appendix-06-newest-features.md
+++ b/second-edition/src/appendix-06-newest-features.md
@@ -112,3 +112,18 @@ fn main() {
 
 The `...` syntax is still accepted in matches, but it is not accepted in
 expressions. `..=` should be preferred.
+
+## 128-bit integers
+
+Rust 1.26.0 added 128-bit integer primitives:
+
+- `u128`: A 128-bit unsigned integer with range [0, 2^128 - 1]
+- `i128`: A 128-bit signed integer with range [-(2^127), 2^127 - 1]
+
+These primitive are implemented efficiently via LLVM support. They
+are available even on platforms that don't natively support 128-bit
+integers and can be used like the other integer types.
+
+These primitives can be very useful for algorithms that need to use
+very large integers efficiently, such as certain cryptographic
+algorithms.