diff --git a/readme.md b/readme.md
index 201b875..451bd60 100644
--- a/readme.md
+++ b/readme.md
@@ -4,12 +4,17 @@ Ed25519
 This is a portable implementation of [Ed25519](http://ed25519.cr.yp.to/). All
 code is in the public domain.
 
+No code uses libc, except for the random seed generation which uses standard
+OS cryptography APIs. If you wish to be entirely portable define
+`ED25519_NO_SEED`. This does disable the `ed25519_create_seed` function
+however.
+
 Usage
 -----
 
 Simply add all .c and .h files in the src/ folder to your project and include
-ed25519.h. If you prefer to use a dll, only copy ed25519.h and define
-ED25519_DLL before importing.
+ed25519.h. If you prefer to use a shared library, only copy `ed25519.h` and define
+`ED25519_DLL` before importing. A windows DLL is pre-built.
 
 The API is simple: