2 ms·

ISBN 9781430265719: "To get the current date/time information, the EPID manager requests a real-time OCSP (Online Certificate Status Protocol) response from a

by cwillu 10y ago

ISBN 9781430265719: "To get the current date/time information, the EPID manager requests a real-time OCSP (Online Certificate Status Protocol) response from a trusted OCSP server, which was endorsed by Intel. The response contains the current date/time. The EPID manager saves the date/time (baseline) in a file in the kernel’s secure storage and calls the kernel’s Start timer function that starts the timer. Later, when the EPID manager is verifying the validity period of a certificate, it calls the Get current timer value function and calculates the current date/time by adding the kernel’s returned value to the baseline. The EPID manager requests a new real-time OCSP response every 30 days to calibrate its timer."

cwillu 10y ago
Tangental, but interesting in a The-Dystopian-Future-Is-Now! sense: "The endorsement key initially placed in security fuses may be revoked by the TPM2_ChangeEPS command introduced in TPM 2.0. In this case, the TPM must generate a new endorsement key pair, store it in nonvolatile memory, and remember not to use the one in the security fuses in the future. The TPM task uses a field programmable fuse for the purpose of saving the revocation status of the endorsement key in fuses." The fuses are blown when the chip is manufactured to encode a _pre-calculated_ 2048-bit rsa key-pair, selected from a giant collection which intel generated en-mass to have some properties that allow the two 1024-bit primes to be encoded using only 272 bits each (if I'm reading it right): "The TPM on the security and management engine features a preinstalled endorsement key (2048-bit RSA). The endorsement key is required to be unique per hardware part. Because of its uniqueness, the endorsement key cannot simply be hard-coded in the firmware, which is the same on all parts. Instead, hundreds of millions of endorsement keys are pregenerated. During Intel’s manufacturing process, different key materials are burned to the platform’s security fuses for all parts, respectively. Note that key materials are not the key value. [...] This algorithm is implemented by the key generation facility and not the TPM firmware." (Same source as parent)

by cwillu 10y ago

cwillu 10y ago

Tangental, but interesting in a The-Dystopian-Future-Is-Now! sense: "The endorsement key initially placed in security fuses may be revoked by the TPM2_ChangeEPS command introduced in TPM 2.0. In this case, the TPM must generate a new endorsement key pair, store it in nonvolatile memory, and remember not to use the one in the security fuses in the future. The TPM task uses a field programmable fuse for the purpose of saving the revocation status of the endorsement key in fuses." The fuses are blown when the chip is manufactured to encode a _pre-calculated_ 2048-bit rsa key-pair, selected from a giant collection which intel generated en-mass to have some properties that allow the two 1024-bit primes to be encoded using only 272 bits each (if I'm reading it right): "The TPM on the security and management engine features a preinstalled endorsement key (2048-bit RSA). The endorsement key is required to be unique per hardware part. Because of its uniqueness, the endorsement key cannot simply be hard-coded in the firmware, which is the same on all parts. Instead, hundreds of millions of endorsement keys are pregenerated. During Intel’s manufacturing process, different key materials are burned to the platform’s security fuses for all parts, respectively. Note that key materials are not the key value. [...] This algorithm is implemented by the key generation facility and not the TPM firmware." (Same source as parent)