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David Benjamin f109f20873 Clear out a bunch of -Wextra-semi warnings. 
Unfortunately, it's not enough to be able to turn it on thanks to the
PURE_VIRTUAL macro. But it gets us most of the way there.

Change-Id: Ie6ad5119fcfd420115fa49d7312f3586890244f4
Reviewed-on: https://boringssl-review.googlesource.com/c/34949
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: Adam Langley <agl@google.com>
2019-02-21 19:12:39 +00:00
..
BUILD.gn Add files in third_party/fiat for Chromium to pick up. 2018-01-10 22:02:03 +00:00
curve25519_32.h Rename Fiat include files to end in .h 2019-01-21 17:29:45 +00:00
curve25519_64.h Rename Fiat include files to end in .h 2019-01-21 17:29:45 +00:00
curve25519_tables.h Use 51-bit limbs from fiat-crypto in 64-bit. 2018-01-23 22:25:07 +00:00
curve25519.c Fix signed left-shifts in curve25519.c. 2019-01-22 23:27:34 +00:00
internal.h Remove x86_64 x25519 assembly. 2018-02-01 21:44:58 +00:00
LICENSE
make_curve25519_tables.py Use 51-bit limbs from fiat-crypto in 64-bit. 2018-01-23 22:25:07 +00:00
METADATA Switch to new fiat pipeline. 2019-01-18 00:24:03 +00:00
p256_32.h Rename Fiat include files to end in .h 2019-01-21 17:29:45 +00:00
p256_64.h Rename Fiat include files to end in .h 2019-01-21 17:29:45 +00:00
p256.c Clear out a bunch of -Wextra-semi warnings. 2019-02-21 19:12:39 +00:00
README.chromium Add files in third_party/fiat for Chromium to pick up. 2018-01-10 22:02:03 +00:00
README.md Use 51-bit limbs from fiat-crypto in 64-bit. 2018-01-23 22:25:07 +00:00

README.md

Fiat

Some of the code in this directory is generated by Fiat and thus these files are licensed under the MIT license. (See LICENSE file.)

Curve25519

To generate the field arithmetic procedures in curve25519.c from a fiat-crypto checkout (as of 7892c66d5e0e5770c79463ce551193ceef870641), run make src/Specific/solinas32_2e255m19_10limbs/femul.c (replacing femul with the desired field operation). The "source" file specifying the finite field and referencing the desired implementation strategy is src/Specific/solinas32_2e255m19_10limbs/CurveParameters.v, specifying roughly "unsaturated arithmetic modulo 2^255-19 using 10 limbs of radix 2^25.5 in 32-bit unsigned integers with a single carry chain and two wraparound carries" where only the prime is considered normative and everything else is treated as "compiler hints".

The 64-bit implementation uses 5 limbs of radix 2^51 with instruction scheduling taken from curve25519-donna-c64. It is found in src/Specific/solinas64_2e255m19_5limbs_donna.

P256

To generate the field arithmetic procedures in p256.c from a fiat-crypto checkout, run make src/Specific/montgomery64_2e256m2e224p2e192p2e96m1_4limbs/femul.c. The corresponding "source" file is src/Specific/montgomery64_2e256m2e224p2e192p2e96m1_4limbs/CurveParameters.v, specifying roughly "64-bit saturated word-by-word Montgomery reduction modulo 2^256 - 2^224 + 2^192 + 2^96 - 1". Again, everything except for the prime is untrusted. There is currently a known issue where fesub.c for p256 does not manage to complete the build (specialization) within a week on Coq 8.7.0. https://github.com/JasonGross/fiat-crypto/tree/3e6851ddecaac70d0feb484a75360d57f6e41244/src/Specific/montgomery64_2e256m2e224p2e192p2e96m1_4limbs does manage to build that file, but the work on that branch was never finished (the correctness proofs of implementation templates still apply, but the now abandoned prototype specialization facilities there are unverified).

Working With Fiat Crypto Field Arithmetic

The fiat-crypto readme https://github.com/mit-plv/fiat-crypto#arithmetic-core contains an overview of the implementation templates followed by a tour of the specialization machinery. It may be helpful to first read about the less messy parts of the system from chapter 3 of http://adam.chlipala.net/theses/andreser.pdf. There is work ongoing to replace the entire specialization mechanism with something much more principled https://github.com/mit-plv/fiat-crypto/projects/4.