Securing non-volatile memory by restricting data width and eliminating direct readbacks

A security system for protecting secret data in a non-volatile memory (NVM) of an authentication integrated circuit (IC), comprising:

• the NVM comprising a native data width of N bits;
• a secret data region in the NVM configured to store secret data at the native data width of N bits;
• a public data region in the NVM configured to store public data at a reduced data width of M bits, where M is less than N;
• and
• a public data interface having a maximum data width of M bits to physically limit access to only M bits of any N-bit data word in either the secret data region or the public data region of the NVM when accessed through the public data interface.

A security system for protecting secret data in a non-volatile memory (NVM) of an authentication integrated circuit (IC), comprising:

• the NVM comprising a native data width of N bits, with a secret data region and a public data region;
• an arbiter circuit coupled to the NVM and configured to control access based on a lifecycle state of the authentication IC;
• a non-invertible function circuit coupled to the arbiter circuit;
• and
• a public data interface having a maximum data width of M bits, where M is less than N;
• wherein the arbiter circuit is configured to:
• during a manufacturing lifecycle state, replace any direct readback of secret data from the secret data region with an output from the non-invertible function circuit, the output computed based on the secret data;
• and
• restrict the public data interface to access only M bits of any N-bit data word in the NVM.