eldo_user

Eldo Netlist Setup
Protection of Encrypted Libraries
• Safety guarantee
The .SEMITRANSPARENT command is effective only if it is found at the beginning of
the deciphered content of an encrypted block. The semi-transparency property only
applies to the content of the very same encrypted block. This constraint guarantees that
it is not possible to transfer the semi-transparency property to encrypted blocks that were
not semi-transparently encrypted. The Eldo encryption scheme guarantees that there is
no way for an attacker to decipher or modify the content of an existing encrypted block
without computing the Eldo key. There is no way for an attacker to prepend
.SEMITRANSPARENT to the content of an encrypted block in order to make it semitransparent.
• User-defined semi-transparent encrypted block
You can manually insert .SEMITRANSPARENT as the first command of a subcircuit
definition or a protected block. As long as the command is in plain-text it is discarded by
Eldo. But once the circuit netlist is encrypted (using the encrypt_eldo utility), the
commands are processed by Eldo as if they appear at the proper location. If you specify
the encrypt_eldo utility without the -semi argument, then the only semi-transparent
blocks generated are those you manually annotated.
The additional encrypt_eldo utility -nosemi argument produces non-semi-transparent
encrypted blocks, discarding any user annotation. It is equivalent to removing every
.SEMITRANSPARENT command from the input file before encrypting it.
• Semi-transparent encryption of Verilog-A blocks.
Examples
Verilog-A modules embedded in a SPICE netlist, using the .INLINE command or
described in a separate file, can be encrypted using the same mechanism above. Module
internal nodes and variables are given public visibility while keeping the
implementation private. To encrypt a Verilog-A file, specify the encrypt_eldo utility
with the -veriloga argument.
Only protected modules that have the Verilog `pragma protect viewport compiler
directive defined before the `pragma protect begin directives, will be encrypted in a
semi-transparent way. The other modules that do not have this directive before the
`pragma protect begin are encrypted in a standard way. The encrypt_eldo utility -semi
argument is not mandatory to achieve semi-transparent encryption of Verilog-A
modules. If this argument is specified then all modules to be encrypted in a file are done
so in a semi-transparent way.
The .SEMITRANSPARENT command is optional if the encrypt_eldo utility is specified with
the -semi argument. .MODEL commands must be included inside a .PROTECT or a .SUBCKT
statement in order for them to be semi-transparently encrypted. For example, to encrypt a model
semi-transparently, pass the following commands to the encrypt_eldo utility:
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Eldo® User's Manual, 15.3