A Security Scheme for Dependable Key Insertion in Mobile Embedded Devices

Algorithm 4

Initialization step for mediated key flashing.

Requirements

  (i) OEM has knowledge of VK_SP and VK_TRKM

Protocol

Step  I.1: SPE presents his credential CRED_SPE and SP authenticates SPE. After that SP

    is activated and communication to OEM is enabled.

Step  I.2: SP creates a new key pair (SK^TD_𝚂𝙿,VK^TD_𝚂𝙿) and sends its ID together with the created

   verification key VK^TD_𝚂𝙿 as a signed request [𝚂𝚒𝚐_SK𝚂𝙿(VK^TD_𝚂𝙿),VK_𝚂𝙿] for a trust credential to OEM.

Step  I.3: OEM verifies that SP and the respective verification key VK_SP is

   listed in the internal database of trusted mediators and that V(𝚂𝚒𝚐_SK𝚂𝙿(VK^TD_𝚂𝙿),VK_𝚂𝙿)=^!1.

   In this case OEM creates a trust delegation credential 𝚂𝚒𝚐_{SK𝙾𝙴𝙼}(VK^TD_𝚂𝙿,VK_𝚂𝙿,𝑇,𝑁) bound to SP

   with timestamp 𝑇 and number of granted transactions 𝑁 and sends it to SP.

Step  I.4: SP receives 𝚂𝚒𝚐_{SK𝙾𝙴𝙼}(VK_𝚂𝙿,VK^TD_𝚂𝙿,𝑇,𝑁) and stores it in the trusted storage.

   This step completes the trust delegation for flashing.

Step  II.1: For a number of TRK_new to be flashed, SP reads out the respective certified

   verification keys 𝚂𝚒𝚐_{SK𝚃𝚁𝙺𝙼}(VK_{𝚃𝚁𝙺new}) and sends 𝚂𝚒𝚐_SK𝚂𝙿(𝚂𝚒𝚐_{SK𝚃𝚁𝙺𝙼}(VK_{𝚃𝚁𝙺new})) to OEM.

Step  II.2: OEM verifies that VK_SP and VK_TRKM are in the internal

   database of trusted peers and that V(𝚂𝚒𝚐_SK𝚂𝙿(𝚂𝚒𝚐_{SK𝚃𝚁𝙺𝙼}(VK_{𝚃𝚁𝙺new})),VK_𝚂𝙿)=^!1 and

   V(𝚂𝚒𝚐_{SK𝚃𝚁𝙺𝙼}(VK_{𝚃𝚁𝙺new}),VK_{𝚃𝚁𝙺𝙼})=^!1. Afterwards OEM creates 𝚂𝚒𝚐_{SK𝙾𝙴𝙼}(VK_{𝚃𝚁𝙺new},VK_SP)

   and sends it to SP.

Step  II.3: SP receives 𝚂𝚒𝚐_{SK𝙾𝙴𝙼}(VK_{𝚃𝚁𝙺new},VK_𝚂𝙿) and stores it in the trusted storage.

   This step completes the activation of the transponder TRK_new for flashing over SP.