Comments on: Is Your SSL Certificate Signed Using Vulnerable MD5? http://hostingfu.com/article/your-ssl-certificates-signed-using-vulnerable-md5 Web Hosting Blog by a Software Developer Fri, 02 Jul 2010 10:59:16 +0000 hourly 1 http://wordpress.org/?v=3.0 By: beamq http://hostingfu.com/article/your-ssl-certificates-signed-using-vulnerable-md5/comment-page-1#comment-970 beamq Thu, 30 Jul 2009 03:00:17 +0000 http://hostingfu.com/?p=179#comment-970 <p>Most of our sites are using MD5. What can we do ? </p> Most of our sites are using MD5. What can we do ?

]]> By: Anonymous http://hostingfu.com/article/your-ssl-certificates-signed-using-vulnerable-md5/comment-page-1#comment-969 Anonymous Mon, 05 Jan 2009 17:26:06 +0000 http://hostingfu.com/?p=179#comment-969 <p>The problem is, it doesn't matter so much that your site uses SHA1 - if any registrar, anywhere, uses MD5, then your site (which is happily using a SHA1 cert on a sane registrar) can be spoofed. In fact, your site using MD5 isn't really useful - if you read the attack paper, they need to predict the serial number of the certificate some time ahead in order to produce the so-called 'birthday block' that they need to convince the CA to embed into the certificate.</p> <p>So, as a user, you should tell your browser not to trust MD5. And as a webmaster, you should make sure you're not using MD5, because it won't be long before browsers stop accepting it. But it's not about 'safety' for the website itself; until browsers lock down MD5, <em>everyone</em> is vulnerable.</p> The problem is, it doesn’t matter so much that your site uses SHA1 – if any registrar, anywhere, uses MD5, then your site (which is happily using a SHA1 cert on a sane registrar) can be spoofed. In fact, your site using MD5 isn’t really useful – if you read the attack paper, they need to predict the serial number of the certificate some time ahead in order to produce the so-called ‘birthday block’ that they need to convince the CA to embed into the certificate.

So, as a user, you should tell your browser not to trust MD5. And as a webmaster, you should make sure you’re not using MD5, because it won’t be long before browsers stop accepting it. But it’s not about ‘safety’ for the website itself; until browsers lock down MD5, everyone is vulnerable.

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