SAE: Increase security parameter k to 40 based on Dragonfly recommendation

draft-irtf-cfrg-dragonfly recommends implementation to set the security
parameter, k, to a value of at least 40. This will make PWE generation
take significantly more resources, but makes it more likely to hide
timing differences due to different number of loops needed to find a
suitable PWE.

Signed-off-by: Jouni Malinen <j@w1.fi>

src/common/sae.c

@@ -290,7 +290,7 @@ static int sae_derive_pwe_ecc(struct sae_data *sae, const u8 *addr1,
 			      const u8 *addr2, const u8 *password,
 			      size_t password_len)
 {
-	u8 counter, k = 4;
+	u8 counter, k = 40;
 	u8 addrs[2 * ETH_ALEN];
 	const u8 *addr[2];
 	size_t len[2];