Castles Technology Co., Ltd.
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4.1.2. ULD User Key
ULD User Key are used to encrypt and sign the user/shared applications.
In addition, they are as goalkeepers to prevent the system updating
without user permission. This is done by the kernel CAPs which are
encrypted and signed by the manufacturer having to perform the “signed’
action via ULD User Keys.
Notes: Applications are encrypted by a random-generated 3DES key,
which is retrieved from the Key Encryption Block of the CAP by ULD User
Key Encryption Key, not directly encrypted by ULD RSA Key.
4.1.3. Key Change
The ULD RSA Keys are able to be changed. The system uses a special
CAP file, KEY CAP, for the manufacturer and user to change their own
keys. The KEY CAP contains a new set of ULD keys (Key Encryption Key
and Signature Key). These new keys are encrypted and signed via the
original keys. In other words, if the user would like to change the ULD
User Keys, they have to use their original ULD User Keys with the new
ULD User Keys to generate a KEY CAP.
Original ULD
Manufacturer/User
Keys
New ULD
Manufacturer/User
Keys
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