Add Optimized and HOL Light verified AVX2 Keccak x4

[manastasova]

Issues:

Import AVX2 Optimized and HOL Light verified 4x Keccak permutation awslabs/s2n-bignum#354

NOTE:: Once awslabs/s2n-bignum#354 is merged, the assembly files would be imported directly with the importer script.

Description of changes:

This PR introduces an optimized AVX2 implementation of the Keccak-f[1600] x4 permutation, formally verified using HOL Light. This batched Keccak implementation processes four independent Keccak permutations in parallel using AVX2 SIMD instructions, significantly accelerating the core hash operations underlying ML-KEM (FIPS 203) and ML-DSA (FIPS 204).

The 4-way parallel Keccak permutation is a critical building block for lattice-based cryptographic schemes, as it is heavily used in:

• ML-KEM: Matrix/vector sampling, seed expansion, and hash operations during keygen, encapsulation, and decapsulation
• ML-DSA: Key generation, signing (rejection sampling), and verification

Performance Results

The optimization delivers substantial throughput improvements across all tested EC2 instance types:

Average Speedups by Algorithm Family:

Algorithm	c7i	c7a	c6i	c6a
ML-KEM-512	+29.2%	+38.7%	+41.4%	+37.6%
ML-KEM-768	+29.3%	+37.6%	+37.4%	+37.4%
ML-KEM-1024	+34.8%	+46.7%	+51.0%	+48.4%
MLDSA44	+16.6%	+17.9%	+23.0%	+21.1%
MLDSA65	+19.6%	+18.4%	+23.9%	+20.8%
MLDSA87	+28.5%	+28.0%	+34.7%	+31.9%

Notable highlights:

• Peak speedup of +59.0% for ML-KEM-1024 keygen on c6i
• ML-KEM-1024 benefits the most across all platforms (up to +52.7% on c7a), as larger parameter sets invoke more Keccak calls
• MLDSA signing shows modest gains (+2–13%) since its runtime is dominated by rejection sampling rather than Keccak permutation throughput
• Improvements are consistent across both Intel and AMD platforms and across both current (Gen 7) and previous generation (Gen 6) instances

Call-outs:

• Reviewers should pay attention to the integration points where the new Keccak x4 is wired into the ML-KEM and ML-DSA call paths

Testing:

• All existing ML-KEM and ML-DSA KAT (Known Answer Tests) pass, confirming functional correctness
  ./crypto/crypto_test
• Performance benchmarked using ./tool/bssl speed on four EC2 instance types (c7i, c7a, c6i, c6a) to validate throughput improvements
  tool/bssl speed -filter "ML-KEM"
tool/bssl speed -filter "MLDSA"

More Performance Data

EC2 c7i

Algorithm	Operation	Original (ops/sec)	New (ops/sec)	Speedup
ML-KEM-512	keygen	102,039.0	137,883.4	+35.1%
ML-KEM-512	encaps	92,432.1	118,961.3	+28.7%
ML-KEM-512	decaps	77,155.5	95,523.5	+23.8%
ML-KEM-768	keygen	65,240.3	86,148.5	+32.1%
ML-KEM-768	encaps	60,583.8	79,416.7	+31.1%
ML-KEM-768	decaps	51,275.5	64,007.9	+24.8%
ML-KEM-1024	keygen	43,752.6	62,079.1	+41.9%
ML-KEM-1024	encaps	40,528.9	54,745.9	+35.1%
ML-KEM-1024	decaps	35,182.9	44,833.4	+27.4%
MLDSA44	keygen	19,594.8	23,784.0	+21.4%
MLDSA44	signing	4,776.1	5,105.4	+6.9%
MLDSA44	verify	18,485.0	22,439.7	+21.4%
MLDSA65	keygen	10,078.2	12,485.9	+23.9%
MLDSA65	signing	3,030.3	3,263.0	+7.7%
MLDSA65	verify	11,629.3	14,807.7	+27.3%
MLDSA87	keygen	7,177.4	9,908.2	+38.0%
MLDSA87	signing	2,534.6	2,776.0	+9.5%
MLDSA87	verify	7,049.3	9,737.1	+38.1%

EC2 c7a

Algorithm	Operation	Original (ops/sec)	New (ops/sec)	Speedup
ML-KEM-512	keygen	94,563.7	137,392.5	+45.3%
ML-KEM-512	encaps	85,020.5	118,473.0	+39.3%
ML-KEM-512	decaps	71,284.2	93,645.4	+31.4%
ML-KEM-768	keygen	56,037.5	79,772.7	+42.4%
ML-KEM-768	encaps	52,744.2	73,353.1	+39.1%
ML-KEM-768	decaps	44,832.4	58,874.9	+31.3%
ML-KEM-1024	keygen	37,007.2	56,511.5	+52.7%
ML-KEM-1024	encaps	34,843.2	51,659.7	+48.3%
ML-KEM-1024	decaps	30,052.9	41,833.0	+39.2%
MLDSA44	keygen	17,087.6	21,781.5	+27.5%
MLDSA44	signing	3,833.2	3,941.9	+2.8%
MLDSA44	verify	15,055.9	18,594.2	+23.5%
MLDSA65	keygen	9,295.8	11,665.2	+25.5%
MLDSA65	signing	2,418.1	2,468.3	+2.1%
MLDSA65	verify	9,658.5	12,321.2	+27.6%
MLDSA87	keygen	6,458.0	9,079.5	+40.6%
MLDSA87	signing	2,021.0	2,147.5	+6.3%
MLDSA87	verify	6,094.7	8,355.6	+37.1%

EC2 c6i

Algorithm	Operation	Original (ops/sec)	New (ops/sec)	Speedup
ML-KEM-512	keygen	74,243.5	110,577.2	+48.9%
ML-KEM-512	encaps	66,855.4	94,949.4	+42.0%
ML-KEM-512	decaps	56,641.7	75,435.7	+33.2%
ML-KEM-768	keygen	44,861.7	63,758.2	+42.1%
ML-KEM-768	encaps	42,938.1	59,149.7	+37.7%
ML-KEM-768	decaps	35,953.7	47,646.6	+32.5%
ML-KEM-1024	keygen	30,333.7	48,230.3	+59.0%
ML-KEM-1024	encaps	28,685.5	43,577.8	+51.9%
ML-KEM-1024	decaps	23,941.1	33,996.0	+42.0%
MLDSA44	keygen	14,708.0	19,526.7	+32.8%
MLDSA44	signing	3,488.7	3,693.8	+5.9%
MLDSA44	verify	13,581.8	17,702.9	+30.3%
MLDSA65	keygen	7,868.8	10,223.9	+29.9%
MLDSA65	signing	2,153.5	2,309.9	+7.3%
MLDSA65	verify	8,542.6	11,490.7	+34.5%
MLDSA87	keygen	5,428.8	8,082.0	+48.9%
MLDSA87	signing	1,819.2	1,973.5	+8.5%
MLDSA87	verify	5,258.6	7,708.2	+46.6%

EC2 c6a

Algorithm	Operation	Original (ops/sec)	New (ops/sec)	Speedup
ML-KEM-512	keygen	94,817.9	138,020.5	+45.6%
ML-KEM-512	encaps	87,240.8	120,129.4	+37.7%
ML-KEM-512	decaps	72,457.8	93,790.5	+29.4%
ML-KEM-768	keygen	60,954.7	87,137.1	+42.9%
ML-KEM-768	encaps	57,065.8	79,197.9	+38.8%
ML-KEM-768	decaps	47,498.6	62,029.9	+30.6%
ML-KEM-1024	keygen	41,115.4	64,320.3	+56.4%
ML-KEM-1024	encaps	38,250.1	57,234.5	+49.6%
ML-KEM-1024	decaps	32,493.6	45,190.5	+39.1%
MLDSA44	keygen	16,540.2	21,594.4	+30.6%
MLDSA44	signing	3,670.8	3,916.2	+6.7%
MLDSA44	verify	14,447.5	18,216.4	+26.1%
MLDSA65	keygen	8,977.5	11,496.0	+28.0%
MLDSA65	signing	2,346.1	2,422.6	+3.3%
MLDSA65	verify	9,377.8	12,294.7	+31.1%
MLDSA87	keygen	6,224.4	8,939.6	+43.6%
MLDSA87	signing	1,961.1	2,208.0	+12.6%
MLDSA87	verify	5,862.3	8,183.7	+39.6%

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.34%. Comparing base (c6d7b33) to head (ee4fc2f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3020      +/-   ##
==========================================
- Coverage   78.51%   78.34%   -0.18%     
==========================================
  Files         689      689              
  Lines      121018   121019       +1     
  Branches    16999    16969      -30     
==========================================
- Hits        95021    94809     -212     
- Misses      25097    25315     +218     
+ Partials      900      895       -5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[sgmenda]

@manastasova is this ready for review or waiting on the s2n-bignum merge?