Why should this vulnerability be considered important?
The vulnerable hardware is mostly to be found within corporate computers from manufacturers such as HP, Fujitsu and Lenovo. Google Chromebooks, routers and some Internet of Things (IoT)(defined). The vulnerability allows an attacker to determine a private (defined) encryption key when it has been generated by a vulnerable TPM (Trusted Platform Module) using only the public key (defined). Once the private key has been obtained it can be used by an attacker to decrypt the contents of a Microsoft BitLocker encrypted hard drive, to digitally sign fake software releases, to sign malware (making it appear more legitimate) as well impersonating the legitimate owner of the private key.
This vulnerability also affects cryptographic smart cards, security tokens and other secure hardware chips manufactured by Infineon. An estimate 760k devices are thought to be vulnerable while the true number could be up to three times that amount.
While the researchers were able to verify an attacker could derive the private key from 1024 and 2048 but public key, they were unable to do so for 4096 bit key since “a 4096-bit RSA key is not practically factorizable now, but “may become so, if the attack is improved.” For 1024 and 2048 bit keys, the factorisation can be easily parallelised by x number of CPUs, reducing the time taken by x times (where x is the number of cores a CPU has) allowing completion in hour or days.
How can I protect myself from this vulnerability?
Microsoft’s advisory provides the recommended steps for systems using Windows or other Microsoft products e.g. Active Directory Certificate Services (ADCS), Active Directory Directory Services (ADDS) (among others). The updates they recommend are only a workaround for the vulnerability. The vulnerability must still be resolved by applying updates to the vulnerable TPM chips. This advice also includes clearing the TPM and re-generating the necessary keys only after applying the updates from Microsoft.
Similarly Google made available Chrome OS M60 to mitigate this vulnerability. Further links to other affected vendors are listed below: