diff --git a/src/_arx.ts b/src/_arx.ts
index 5a05b6b..f182246 100644
--- a/src/_arx.ts
+++ b/src/_arx.ts
@@ -44,6 +44,7 @@ const sigma16 = _utf8ToBytes('expand 16-byte k');
 const sigma32 = _utf8ToBytes('expand 32-byte k');
 const sigma16_32 = u32(sigma16);
 const sigma32_32 = u32(sigma32);
+export const sigma = sigma32_32.slice();
 
 export function rotl(a: number, b: number): number {
   return (a << b) | (a >>> (32 - b));