openbsd/src/lib/libcrypto/ec, branch OPENBSD_7_8_BASEA mirror of https://github.com/libressl/openbsd.git
https://git.lua4.win/openbsd/atom?h=OPENBSD_7_8_BASE2025-08-26T14:14:52+00:00ec_mult.c: place this code under my ISC license2025-08-26T14:14:52+00:00tb2025-08-26T14:14:52+00:00urn:sha1:b54b551b03de5db0750e0fffc1a4ad3389fd28d3
I have effectively rewritten the entirety of this file end of 2024.
This isn't code I'm particularly proud of, but it's much better than
it was before (it's not as if that involved any sort of challenge...)
requested by/ok jsing
Implement constant time EC scalar multiplication.2025-08-03T15:44:00+00:00jsing2025-08-03T15:44:00+00:00urn:sha1:7037d4c7b0d5603ef79bf7e7f1b33c2cbbce89f2
Replace simplistic non-constant time scalar multiplication with a constant
time version. This is actually faster since we compute multiples of the
point, then double four times and add once. The multiple to add is selected
conditionally, ensuring that the access patterns remain the same regardless
of value.
Inspired by Go's scalar multiplication code.
ok tb@
Remove duplicate computation for b3.2025-08-03T15:08:28+00:00jsing2025-08-03T15:08:28+00:00urn:sha1:862ba5f367a460df8a40dceac15e0369f39cdddfAdd prototype for EC_GFp_homogeneous_projective_method().2025-08-03T15:07:57+00:00jsing2025-08-03T15:07:57+00:00urn:sha1:bf229b0023f2f085d216bc2e742c6b48c7afe2b9Provide bn_mod_sqr_words() and call it from ec_field_element_sqr().2025-08-02T16:20:00+00:00jsing2025-08-02T16:20:00+00:00urn:sha1:39d33c1bb185014e05def87e04f21103d92dc455
For now this still calls bn_montgomery_multiply_words(), however it can
be optimised further in the future.
Copy EC_FIELD_MODULUS/EC_FIELD_ELEMENTs when copying groups and points.2025-08-02T15:47:27+00:00jsing2025-08-02T15:47:27+00:00urn:sha1:ad3c9e6996dc8c88567319b6291785b4c0bb15c4
ok tb@
Provide constant time conditional selection between EC_FIELD_ELEMENTs.2025-08-02T15:44:09+00:00jsing2025-08-02T15:44:09+00:00urn:sha1:1c7727d98f4279760cde2908bbfe7e06b323c209
Provide a ec_field_element_select() function that allows for constant time
conditional selection between two EC_FIELD_ELEMENTs. This will become a
building block for constant time point multiplication.
ok tb@
Fix resource leaks in ec_points_make_affine()2025-06-01T03:23:33+00:00tb2025-06-01T03:23:33+00:00urn:sha1:5df8087a42612332d095e39b6e5aa10e6a909eed
Add missing BN_CTX_end() and free prod_Z.
CID 552848 (for prod_Z)
Remove bogus alias.2025-05-25T05:43:33+00:00jsing2025-05-25T05:43:33+00:00urn:sha1:093fd1537f471c36878b48ca845f9f073d7bce93Provide an EC method that uses homogeneous projective coordinates.2025-05-25T05:19:26+00:00jsing2025-05-25T05:19:26+00:00urn:sha1:26512301343d2b40a68a67d4f4175ddec368d2fe
This makes use of EC_FIELD_ELEMENT to perform fixed width constant
time operations.
Addition and doubling of points makes use of the formulas from
"Complete addition formulas for prime order elliptic curves"
(https://eprint.iacr.org/2015/1060). These are complete and
operate in constant time.
Further work will continue in tree.
ok tb@