Commit 1e368ab0 authored by Dr. Stephen Henson's avatar Dr. Stephen Henson
Browse files

Fix the ECDSA timing attack mentioned in the paper at: 

	http://eprint.iacr.org/2011/232.pdf

Thanks to the original authors Billy Bob Brumley and Nicola Tuveri for
bringing this to our attention.
parent 2c77c5c8

CHANGES

+6 −1
Original line number Diff line number Diff line
@@ -4,7 +4,12 @@ 


 Changes between 0.9.8r and 0.9.8s [xx XXX xxxx]



  *)

  *) Add protection against ECDSA timing attacks as mentioned in the paper

     by Billy Bob Brumley and Nicola Tuveri, see:



	http://eprint.iacr.org/2011/232.pdf



     [Billy Bob Brumley and Nicola Tuveri]



 Changes between 0.9.8q and 0.9.8r [8 Feb 2011]

crypto/ecdsa/ecs_ossl.c

+10 −0
Original line number Diff line number Diff line
@@ -144,6 +144,16 @@ static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp, 
			}

		while (BN_is_zero(k));



#ifdef ECDSA_POINT_MUL_NO_CONSTTIME

		/* We do not want timing information to leak the length of k,

		 * so we compute G*k using an equivalent scalar of fixed

		 * bit-length. */



		if (!BN_add(k, k, order)) goto err;

		if (BN_num_bits(k) <= BN_num_bits(order))

			if (!BN_add(k, k, order)) goto err;

#endif /* def(ECDSA_POINT_MUL_NO_CONSTTIME) */



		/* compute r the x-coordinate of generator * k */

		if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx))

		{