International Association
for Cryptologic Research

We provide the first provable-security analysis of the Intel Secure Key hardware RNG (ISK-RNG), versions of which have appeared in Intel processors since late 2011. To model the ISK-RNG, we generalize the PRNG-with-inputs primitive, introduced Dodis et al. introduced at CCS\'13 for their /dev/[u]random analysis. The concrete security bounds we uncover tell a mixed story. We find that ISK-RNG lacks backward-security altogether, and that the forward-security bound for the ``truly random\'\' bits fetched by the RDSEED instruction is potentially worrisome. On the other hand, we are able to prove stronger forward-security bounds for the pseudorandom bits fetched by the RDRAND instruction. En route to these results, our main technical efforts focus on the way in which ISK-RNG employs CBCMAC as an entropy extractor.