Editing Trusted Computing (section)

==={{anchor|ENDORSEMENT-KEY}}Endorsement key===
The endorsement key is a 2048-bit [[RSA (algorithm)|RSA]] public and private key pair that is created randomly on the chip at manufacture time and cannot be changed. The private key never leaves the chip, while the public key is used for attestation and for encryption of sensitive data sent to the chip, as occurs during the TPM_TakeOwnership command.<ref>{{cite web | author = Safford, David | url = http://www.linuxjournal.com/article/6633 | title = Take Control of TCPA | date = 2003-08-01 | access-date = 2007-02-07 | work = Linux Journal | author-link = David Safford }}</ref>

This key is used to allow the execution of secure transactions: every Trusted Platform Module (TPM) is required to be able to sign a random number (in order to allow the owner to show that he has a genuine trusted computer), using a particular protocol created by the Trusted Computing Group (the [[direct anonymous attestation]] protocol) in order to ensure its compliance of the TCG standard and to prove its identity; this makes it impossible for a software TPM emulator with an untrusted endorsement key (for example, a self-generated one) to start a secure transaction with a trusted entity. The TPM should be{{vague|date=March 2015}} designed to make the extraction of this key by hardware analysis hard, but [[tamper resistance]] is not a strong requirement.