Port gean to devnet-4

[dimka90]

Description

Migrate gean from devnet-3 to devnet-4 covering XMSS crypto migration, dual-key validators, block envelope simplification, recursive aggregation, and fork choice convergence.

Work is structured in phases matching the leanSpec devnet-4 changes.

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Spec Reference

• leanSpec pinned at 16e50a5fcc8be837f09aabf30c92e653bc36dad4

Branch

• devnet-4

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Phases

Phase 1: Crypto Migration

Migrate XMSS from Dim64Base8 (3112-byte signatures) to Dim46Base8 (2536-byte signatures).

• Update hashsig-glue to leansig devnet4 Dim46Base8
• Update SignatureSize in types/constants.go (3112 → 2536)
• Update SSZ offsets:
  • attestation_encoding.go
  • block_encoding.go
• Add prover twiddle precomputation (sumcheck backend)
• Enable AVX2 SIMD build flag (x86_64) with ARM fallback

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Phase 2: Dual-Key Validator Model

• Update Validator struct:
  • AttestationPubkey
  • ProposalPubkey
• Implement KeyManager:
  • SignAttestation
  • SignBlock
• Update genesis config:
  • GenesisValidatorEntry with dual keys
• Implement key generation:
  • annotated_validators.yaml

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Phase 3: Block Envelope Simplification

• Introduce SignedBlock:
  • Block + BlockSignatures
• Remove BlockWithAttestation
• Remove ProposerAttestation
• Update proposer signing:
  • hash_tree_root(block) with proposal key

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Phase 4: CGo Safety

• Add runtime.Pinner in:
  • AggregateWithChildren
  • VerifyAggregatedSignature

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Phase 5: Recursive Aggregation

• Implement Select → Fill → Aggregate

Select

• Greedy selection of existing child proofs

Fill

• Collect raw gossip signatures

Aggregate

• Recursive aggregation via AggregateWithChildren

• Enforce minimum 2 inputs

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Phase 6: Fork Choice Convergence

• Fix vote index remapping:
  • AppliedIndex, LatestKnown, LatestNew
• Drain pending blocks before attestation production
• Call updateHead before proposal
• Add PromoteNewToKnown + updateHead in maybePropose
• Use unbounded payload buffers (prune on finalization)

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Phase 7: Networking

• Drop raw gossip attestations on non-aggregators
• Implement per-validator subnet subscription
• Parse --aggregate-subnet-ids CLI flag
• Aggregator fallback to subnet 0

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Phase 8: Source Alignment

• Use store justified for:
  • Attestation source
  • Builder filtering
• Enforce strict slot-only comparison
• Drain pending attestations before aggregation

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Phase 9: Spec Tests

• Update fixture parser:
  • camelCase (attestationPubkey, proposalPubkey)
• Update signature tests for SignedBlock
• Remove ProposerAttestation from forkchoice tests
• Pin LEAN_SPEC_COMMIT_HASH

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How to Run

make run-setup    # first time: build + generate keys
make run          # terminal 1: aggregator
make run-node1    # terminal 2
make run-node2    # terminal 3