Scaffolding for ML-KEM Decaps (FIPS 203 Alg 18):
- op_i widened to 2-bit: 00=KeyGen, 01=Encaps, 10=Decaps (op_r too).
- New ST_DEC_LOAD state (D0: settles to DONE so load/parse is dbg-checkable).
- dk (=sk) streamed via dk_in_*; load logic routes each byte by region:
[0,384K)->dk_pke (dkp_bram), [384K,768K+32)->ek_pke (ek_bram),
[768K+32,+32)->H(ek) (hek_r), [768K+64,+32)->z (z_r). Routing uses the
LIVE k_i input, not start-captured k_r (dk is streamed before start_i).
- c (=ct) streamed via c_in_* into a SEPARATE c_in_bram, so the computed c'
(ct_bram) can later be compared against original c and J(z||c) can read c.
- New dbg taps: dbg_mprime_o/dbg_kbar_o/dbg_decz_o/dbg_dech_o.
TB: tb_mlkem_dec_katK_xsim verifies dk parse (H(ek), z, ek_pke/dk_pke BRAM
round-trip). gen_decaps_vectors.py emits dec_k{K}_c{N}_{dk,ct,ss,ctn,ssn}.hex
from the NIST KAT. run_tb.sh gains a 'dec' module (mirrors 'enc').
Regression fix: old KeyGen/Encaps TBs didn't connect the new input ports,
floating them to X and corrupting the ek/dkp write muxes -> tied off
dk_in_*/c_in_*/new dbg taps in both.
Verified: dec D0 K=2/3/4 PASS; KeyGen K=2 + Encaps K=2 unregressed.
Extend mlkem_top with a runtime op_i select (0=KeyGen, 1=Encaps) and the
first Encaps stages, reusing the shared keccak_core and the ST_H multi-block
SHA3-256 machinery:
ST_ENC_H: H(ek) over preloaded ek_bram (same FSM as KeyGen ST_H)
ST_ENC_G: (K,r) = G(m||H(ek)) via new 64-byte single-block SHA3-512
- sha3_top_shared: add mode=2'b11 = SHA3-512 over a full 512-bit message
(g512_pad). Standalone tb_sha3_g512 confirms it byte-exact.
- mlkem_top: new ports op_i, msg_i, ek_in_{we,addr,byte} (ek preload), ss_o,
dbg_ct_*, dbg_r_o/dbg_hek_o. st widened 4->5 bits; ST_ENC_* states added.
Renamed message port to msg_i to avoid collision with ST_M counter m_i.
- TB tb_mlkem_enc_katK + gen_encaps_vectors.py (per-byte ek/m/ct/ss vectors).
Verified ss==KAT.ss for K=2/3/4, cases 0-2 (all PASS). KeyGen unaffected
(K=2 c0 still ek==pk, dk==sk byte-exact).
The KAT TB now prints, for each run: the d and z seeds (32-byte hex, MSB-first
== vector file order) before start, and the full ek/dk byte strings read back
from the DUT (32 bytes/line, offset-prefixed) after the byte-compare. Inputs
verified to match the kat_*_d/z.hex files exactly; dk[768..] echoes ek[0..] as
expected (dk_pke || ek || H(ek) || z). Pass/fail logic unchanged.
mlkem_top now sizes storage for KMAX=4 (worst case) and selects the
active ML-KEM parameter set at start_i via the k_i input. All K-derived
quantities (eta1, slot bases, ek/dk byte counts, H(ek) block count, FSM
bounds) are computed at runtime from the captured k_r.
Verified byte-exact against NIST KAT for all three parameter sets:
K=2 (512) cases 0-4, K=3 (768) cases 0-2, K=4 (1024) cases 0-2
-> 11/11 PASS (ek==pk, dk==sk).
