We've worked extensively in this field, primarily to help vendors ship these products more safely --- so we're enjoined against publishing specifics. But it's a real problem, and I'd refer you to IOActive (a competitor of ours) for details.<p>Two things to remember about embedded RF devices and security:<p>* The boards themselves are a hostile environment for developing crypto, because they're solid state (low entropy), severely power constrained, and have very little headroom for code storage; the difference between supporting SHA1 vs. MD5 could come down to blowing the instruction store budget.<p>* RF is a hostile place to deploy crypto, because it's group based, severely rate limited, slow, and every individual bit of message encoding is precious.<p>Very smart developers never get crypto right even in environments where a shift from an MD5 MAC to a digital signature is just a line of code, without regard to message sizes, and where the only constraint against adding protocol steps is breaking compatibility with software that can be upgraded in minutes. Draw your own conclusions about how hard this problem is.<p>(As Nate pointed out a year or two ago, the exact same problem exists with tolling systems).