sg.length = bodysize;
        key = (char *)ep->secret_key[ep->current_key];
 
-       memset(digest, 0x00, sizeof(digest));
+       memset(digest, 0x00, SCTP_SIGNATURE_SIZE);
        sctp_crypto_hmac(sctp_sk(ep->base.sk)->hmac, key, &keylen, &sg,
                         1, digest);
 
        if (memcmp(digest, cookie->signature, SCTP_SIGNATURE_SIZE)) {
                /* Try the previous key. */
                key = (char *)ep->secret_key[ep->last_key];
-               memset(digest, 0x00, sizeof(digest));
+               memset(digest, 0x00, SCTP_SIGNATURE_SIZE);
                sctp_crypto_hmac(sctp_sk(ep->base.sk)->hmac, key, &keylen,
                                 &sg, 1, digest);