Added link to ecc64.
diff --git a/index.md b/index.md
index 4ace531..e0b01e7 100644
--- a/index.md
+++ b/index.md
@@ -6,7 +6,7 @@
 micro-ecc
 ==========
 
-A small ECDH and ECDSA implementation for 32-bit microcontrollers.
+A small ECDH and ECDSA implementation for 32-bit microcontrollers. See [ecc64](http://kmackay.ca/ecc64) for a 64-bit implementation.
 
 Features
 --------