User's Manual

4. Secure File Loading

Castles implemented an interface in terminal named User Loader(ULD) to provide secure file

loading to system memory. Loading of user application, kernel firmware, font and others

must use User Loader.

The loading process is secure by signing the files using ULD Key System.

4.1. ULD Key System

The ULD Key System uses two key sets for securely managing the kernel

updating and application downloading. Each key set contains two RSA key pairs.

One is used for key encryption and the other is used for signature. These two key

sets are specified as below:

ULD Manufacturer Key Set

 ULD Manufacturer Key Encryption Key (RSA)

 ULD Manufacturer Signature Key (RSA)

ULD User Key Set

 ULD User Key Encryption Key (RSA)

 ULD User Signature Key (RSA)

For VEGA5000S, the RSA key length is 2048bits.

4.1.1. ULD Manufacturer Key

The system consists of several kernel modules. These kernel modules

are provided by the Manufacturer, and released in CAP format file with

encryption and signing via ULD Manufacturer Keys.

The ULD Manufacturer keys are managed and maintained by the

manufacturer. The manufacturer uses these keys to generate kernel

CAP files for updating the system. However, the system is not permited

to be updated with these kernel CAP files directly generated by the

manufacturer. This is because only the user can have the privilege to

decide whether the system is to be updated. Therefore, before system