On Fri, Dec 03, 2010 at 09:10:41AM -0800, Marcus Carey wrote:
> I am still have issues with the default ECDH parameters in 1.0.0c.
kEECDH handshakes appear to work.
> The key generation with NIST Prime-Curve P-192 crashes.
How do you reproduce this?
> static void nist_cp_bn(BN_ULONG *buf, BN_ULONG *a, int top)
> {
> int i;
> BN_ULONG *_tmp1 = (buf), *_tmp2 = (a);
> for (i = (top); i != 0; i--)
> *_tmp1++ = *_tmp2++; //There is a problem here
> }
The above looks fine, in what context is this called?
The code in crypto/bn/bn_nist.c has not changed since 0.9.8j, it is
different in 0.9.8i.
http://cvs.openssl.org/chngview?cn=17756
I don't understand the code in BN_nist_mod_192(), which calls
nist_cp_bn(), it has rather obscure pointer manipulation:
/*
* we need 'if (carry==0 || result>=modulus) result-=modulus;'
* as comparison implies subtraction, we can write
* 'tmp=result-modulus; if (!carry || !borrow) result=tmp;'
* this is what happens below, but without explicit if:-) a.
*/
mask = 0-(size_t)bn_sub_words(c_d,r_d,_nist_p_192[0],BN_NIST_192_TOP);
mask &= 0-(size_t)carry;
---> res = (BN_ULONG *)(((size_t)c_d&~mask) | ((size_t)r_d&mask));
nist_cp_bn(r_d, res, BN_NIST_192_TOP);
--
Viktor.
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