DS5002FP Secure Microprocessor Chip

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DETAILED DESCRIPTION

The DS5002FP implements a security system that is an improved version of its predecessor, the DS5000FP. Like

the DS5000FP, the DS5002FP loads and executes application software in encrypted form. Up to 128kB of

standard SRAM can be accessed by its byte-wide bus. This RAM is converted by the DS5002FP into lithium-

backed nonvolatile storage for program and data. Data is maintained for over 10 years at room temperature with a

very small lithium cell. As a result, the contents of the RAM and the execution of the software appear unintelligible

to the outside observer. The encryption algorithm uses an internally stored and protected key. Any attempt to

discover the key value results in its erasure, rendering the encrypted contents of the RAM useless.

The secure microprocessor chip offers a number of major enhancements to the software security implemented in

the previous generation DS5000FP. First, the DS5002FP provides a stronger software encryption algorithm that

incorporates elements of DES encryption. Second, the encryption is based on a 64-bit key word, as compared to

the DS5000FP’s 40-bit key. Third, the key can only be loaded from an on-chip true random-number generator. As a

result, the true key value is never known by the user. Fourth, a self-destruct input (SDI) pin is provided to interface

effect as resetting the security lock: immediate erasure of the key word and the 48-byte Vector RAM area. Fifth, an

optional top-coating of the die prevents access of information using microprobing techniques. Finally, customer-

specific versions of the DS5002FP are available that incorporate a one-of-a-kind encryption algorithm.

When implemented as a part of a secure system design, a system based on the DS5002FP can typically provide a

level of security that requires more time and resources to defeat than it is worth to unauthorized individuals who

have reason to try. For a user who wants a preconstructed module using the DS5002FP, RAM, lithium cell, and a

real-time clock, the DS2252T is available and described in a separate data sheet.

BLOCK DIAGRAM

Figure 8 is a block diagram illustrating the internal architecture of the DS5002FP. The DS5002FP is a secure

implementation of the DS5001FP 128k soft microprocessor chip. As a result, it operates in an identical fashion to

the DS5001FP, except where indicated. See the DS5001FP data sheet for operating details.