Patent ID: 11860999

Abstract:
A TPM with programmable fuses in an SOC includes an on-die RAM storing a blown-fuse count and a TPM state including a PIN-attempt-failure count and a fuse count, read from off-die NV memory. During initialization, if the blown-fuse count is greater than TPM state fuse count, TPM state PIN-attempt-failure count is incremented, thereby thwarting a replay attack. A PIN is received for access, and if the TPM state PIN-attempt-failure count satisfies a policy, a fuse is blown and the blown-fuse count incremented. If the fuse blow fails, TPM activity is halted. If the fuse blow succeeds and the PIN is correct, the TPM state PIN-attempt-failure count is cleared, but if the PIN is incorrect the TPM state PIN-attempt-failure count is incremented. TPM state fuse count is set equal to the blown-fuse count, and the TPM state is saved to off-die NV memory.