<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">On Aug 20, 2014, at 7:12 AM, Erwan Legrand <<a href="mailto:erwan@lightbringer.org">erwan@lightbringer.org</a>> wrote:<div><blockquote type="cite"><p dir="ltr">
>This is a rather weak argument. You're contrasting a CSPRNG - something >that's quite difficult to build correctly, as we've seen from many discussions >on this list - with something as simple as "remember the last one and add one >to get the next"....</p></blockquote><blockquote type="cite"><p dir="ltr">As I said, the target audience is web application developpers. These do not write CSPRNG's. Yet many of them write authentication code using a crypto toolkit.</p><p dir="ltr">Does this make sense now?</p>
</blockquote>Sorry, but no. I consider it similar to the following argument: An electrical circuit needs a fuse. But, you know, people might stick the wrong size fuse in there. Or they might even stick in a penny (OK, this style of fuse hasn't been used in 50 years). I can do better. I have a digital voltage sensor, which I can turn into an amperage sensor with a resistor. I can feed that into my Arduino and monitor the current drawn. I'll include a digital model of the kind of fuse that's supposed to go here, so that it lets peaks of the right sort through, etc. Then I'll write a driver to control a relay. Now I've got solid, modern protection for my circuit, and people can't screw it up!</div><div><br></div><div>Replacing a simple design with a more complex one "just because you have the parts around" adds to risk, it doesn't ameliorate it.</div><div><br></div><div>I've written separately - in messages that haven't yet been forwarded to the list; our moderators are likely still asleep - about the actual threats, and that one could argue for using a CSPRNG on "defense in depth" principles, even if the argument is a bit of a stretch. But I don't buy the "it's better engineering because you might screw up code to add 1 to the last number" argument.</div><div><div> -- Jerry</div><div><br></div></div></body></html>