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libhal

This library combines a set of low-level API functions which talk to the Cryptech FPGA cores with a set of higher-level functions providing various cryptographic services.

There's some overlap between the low-level code here and the low-level code in core/platform/novena, which will need sorting out some day, but at the time this library forked that code, the core/platform/novena code was all written to support a test harness rather than a higher-level API.

Current contents of the library:

  • Low-level I/O code (EIM and I2C).

  • An implementation of AES Key Wrap using the Cryptech AES core.

  • An interface to the Cryptech CSPRNG.

  • An interface to the Cryptech hash cores, including HMAC.

  • An implementation of PBPDF2.

  • An implementation of RSA using the Cryptech ModExp core.

  • Test code for all of the above.

Most of these are fairly well self-contained, although the PBKDF2 implementation uses the hash-core-based HMAC implementation.

The major exception is the RSA implementation, which uses an external bignum implementation (libtfm) to handle a lot of the arithmetic. In the long run, much or all of this may end up being implemented in Verilog, but for the moment all of the RSA math except for modular exponentiation is happening in software.

The RSA implementation includes a compile-time option to bypass the ModExp core and do everything in software, because the ModExp core is a tad slow at the moment (others are hard at work fixing this).

The RSA implementation includes optional blinding (enabled by default) and just enough ASN.1 code to read and write private keys; the expectation is that the latter will be used in combination with the AES Key Wrap code.