Note that secp224r1 is now supported.

README.md

diff --git a/README.md b/README.md
index 24f1231..e3049a0 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@
  * Supports 8, 32, and 64-bit architectures.
  * Small code size.
  * No dynamic memory allocation.
- * Support for 4 standard curves: secp160r1, secp192r1, secp256r1, and secp256k1.
+ * Support for 5 standard curves: secp160r1, secp192r1, secp224r1, secp256r1, and secp256k1.
  * BSD 2-clause license.
 
 Usage Notes