diff --git a/library/sha256.c b/library/sha256.c
index 6ae6a0e..9552b8c 100644
--- a/library/sha256.c
+++ b/library/sha256.c
@@ -269,6 +269,12 @@
     for( i = 0; i < 8; i++ )
         ctx->state[i] += A[i];
 
+    /* Zeroise buffers and variables to clear sensitive data from memory. */
+    mbedtls_zeroize( &A, sizeof( A ) );
+    mbedtls_zeroize( &W, sizeof( W ) );
+    mbedtls_zeroize( &temp1, sizeof( temp1 ) );
+    mbedtls_zeroize( &temp2, sizeof( temp2 ) );
+
     return( 0 );
 }