VeriFone Vx810 Reference Manual page 83

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An application stored in Groups 2–15 can only access files stored in its own
file group and in Group 15. For example, an application authorized by the
sponsor to be authenticated in Group 4 can only access files and libraries
stored in Group 4 and Group 15.
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If multiple applications (main and secondary) are to run on the same device,
each .OUT and shared library file must have its own matching signature file.
Because each application is responsible for verifying its own data and prompt
files, the other application files should have their own matching signature files.
The master .OUT file should validate that these additional signature files are
authenticated before they are used.
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If two or more applications will run on the same device, the signature files for
the respective applications must be downloaded, together with the
corresponding target files, into the specific file groups for which the
applications are authorized. If an application is downloaded onto a group for
which is it not authorized, file authentication for that application fails.
If, for example, Application B is downloaded onto GID4, where it is authorized
to run, but the signature files for all Application B executable files are
downloaded onto GID7, file authentication for Application B fails and it is not
allowed to run.
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Each certificate contains an attribute to verify if an application is valid for a
particular group.
Authenticate Files Stored in the SRAM or Flash ROM of a File Group
All *.p7s files are loaded onto SRAM and contain flags that indicate if the file to
verify is stored in SRAM or flash ROM. A signature file must know if its matching
application file is stored in SRAM or flash ROM. If a signature file cannot locate its
matching application file, the application file is not authenticated.
If the signature file authenticates its target file, and if the *FA variable is present in
the config.sys file of the target file group and is set to 1, the signature file is
retained in memory and is automatically moved, if necessary, into the same file
system as the target file it authenticates. That is, if the target file is stored in the
flash ROM, the signature file is also stored in the flash ROM; if the target file is
stored in SRAM, the signature file is also stored in SRAM.
F A
ILE UTHENTICATION
File Authentication and the File System
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