Crate sha256_rhdl 

RHDL SHA-256 compression implementations and performance-lane building blocks. This crate is the hash foundation for the separately typed HASHSIGS_SHA256_GENERIC_V1 profile. It is deliberately incompatible with the legacy Keccak profile.

The correctness path consists of:

• allocation-free, compile-time-capable SHA-256 primitives and compression;
• a byte-oriented padding/block-stream helper;
• an RHDL round kernel whose token carries the eight working words and a sixteen-word rolling message-schedule window;
• an RHDL combinational compression kernel used as a lowering oracle; and
• a resetless round-pipeline foundation with separately reset valid bits; and
• lane::CompressionLane, which aligns the original chaining value in a circular synchronous memory and performs feed-forward; and
• farm::ThreeLaneCompressionFarm, a standalone generation and equivalence target with independent inputs, outputs, tags, and valid streams.

The production WOTS signer does not embed that farm. It uses three autonomous four-context clusters, with one complete compression lane owned by each cluster.

Modules

farm

Parallel compression-lane farm for the performance profile. Parallel SHA-256 compression lanes for the performance profile.

lane

Complete streaming compression-lane implementation. Complete, one-block-per-cycle SHA-256 compression lane.

Structs

PipelineWord

Pipeline payload. state is meaningful only while valid is true.

RoundPipeline

A resetless, fully registered prefix of the 64-round SHA-256 pipeline.

RoundState

Complete 768-bit datapath token for one SHA-256 round.

WorkingState

Eight SHA-256 working variables carried by every round token.

Constants

BLOCKS_FOR_32_BYTES

Padded block count for a 32-byte hash input.

BLOCKS_FOR_35_BYTES

Padded block count for a 35-byte HashSigs PRF input.

BLOCKS_FOR_64_BYTES

Padded block count for a 64-byte secret-segment input.

BLOCKS_FOR_2144_BYTES

Padded block count for the 2,144-byte concatenated public-key segments.

BLOCK_BYTES

SHA-256 compression-block size in bytes.

DIGEST_BYTES

SHA-256 digest size in bytes.

INITIAL_STATE

SHA-256 initial chaining value from FIPS 180-4 section 5.3.3.

LANE_DATAPATH_FFS

Resetless datapath-register count in one complete 64-round lane.

LANE_PIPELINE_FFS

Total round-pipeline registers in one lane, excluding chaining-value memory.

LANE_TAG_FFS

Resetless tag-register count in one complete lane.

LANE_VALID_FFS

Resettable valid-register count in one complete lane.

ROUND_CONSTANTS

The 64 SHA-256 round constants from FIPS 180-4 section 4.2.2.

ROUND_CONSTANTS_RHDL

RHDL-width-preserving form of ROUND_CONSTANTS.

ROUND_COUNT

Number of rounds in one SHA-256 compression operation.

ROUND_TOKEN_BITS

Number of bits in one resetless round-pipeline token.

SCHEDULER_TAG_BITS

Width of the opaque scheduler tag carried beside every pipeline token.

THREE_LANE_DATAPATH_FFS

Provisional resetless datapath-register count in three complete lanes.

THREE_LANE_PIPELINE_FFS

Total round-pipeline registers projected for three lanes.

Functions

big_sigma_one

SHA-256 uppercase sigma one.

big_sigma_one_kernel

RHDL uppercase sigma one with constant rotates.

big_sigma_zero

SHA-256 uppercase sigma zero.

big_sigma_zero_kernel

RHDL uppercase sigma zero with constant rotates.

choose

SHA-256 choice function.

choose_kernel

RHDL SHA-256 choice function.

compress_block

Compresses one block and performs the mandated chaining-value feed-forward.

compression_kernel

RHDL lowering oracle for one complete compression operation.

compression_verilog

Emits the combinational compression oracle as Verilog.

decode_block

Decodes a 64-byte compression block into sixteen big-endian words.

expand_schedule

Expands sixteen input words into the complete 64-word SHA-256 schedule.

feed_forward_kernel

Adds the final working variables to the input chaining value.

majority

SHA-256 majority function.

majority_kernel

RHDL SHA-256 majority function.

padded_block

Produces one padded SHA-256 block from an immutable byte stream.

padded_block_count

Returns the number of 64-byte blocks after SHA-256 padding.

rotate_right

Rotates a software-model word right by a constant or dynamic count.

round_kernel

Executes exactly one SHA-256 round and advances the rolling schedule.

round_pipeline_kernel

Connectivity kernel for RoundPipeline.

round_pipeline_unchecked_verilog

Emits a registered round-pipeline prefix without RHDL’s Icarus syntax check.

round_pipeline_verilog

Emits a registered round-pipeline prefix as Verilog.

round_verilog

Emits the isolated RHDL round kernel as Verilog for synthesis gates.

schedule_kernel

Advances the sixteen-word rolling message-schedule window.

sha256

Hashes one byte slice with the correctness-first software model.

small_sigma_one

SHA-256 lowercase sigma one.

small_sigma_one_kernel

RHDL lowercase sigma one with constant shifts and rotates.

small_sigma_zero

SHA-256 lowercase sigma zero.

small_sigma_zero_kernel

RHDL lowercase sigma zero with constant shifts and rotates.