[s6pa1rta3n-lab]

Summary

Wave Issue Key: ZK-062
Closes #306

Adds a comprehensive deterministic fuzz and property test suite for note serialization, witness and public input encoding, and Merkle path operations in the SDK (sdk/test/zk062_fuzz_property.test.ts).

Test Coverage Highlights

• Note Serialization:
  • Seeded random round-trip invariance for importBackup(exportBackup()) preserving note secrets, scalars, and Poseidon2 commitments across 100 iterations.
  • Legacy format round-trip testing for deserialize(serialize()).
  • Single-bit and single-byte mutation fuzzing across note backup payloads.
  • Structural prefix and payload length fuzzing (INVALID_PREFIX, INVALID_LENGTH, CORRUPT_DATA).
  • Non-hex payload character injection fuzzing.
  • Fixed regressions: corrupted denomination checksum, unsupported version byte 0x02.
• Witness & Public Input Encoding:
  • Round-trip serialization into canonical 256-byte layout and 8-field order (serializeWithdrawalPublicInputs).
  • Soroban contract verifier serialization equivalence (serializeContractVerifierInputs).
  • Circuit input packing equivalence (packWithdrawalPublicInputs).
  • Canonical field hex validation and rejection of non-canonical decimal strings (ZK-082).
  • Stellar address format validation and BN254 field encoding (encodeStellarAddress).
  • Domain-separated nullifier hash determinism (encodeNullifierHash).
  • Fixed regressions: decimal amount string "1000", 63-character hex length in field inputs.
• Merkle Path Integrity:
  • Tree path proof generation and reconstruction against tree roots across multiple depths (3, 4, 6) using stableHash32.
  • Sibling mutation sensitivity (single-bit flips at any level break root reconstruction).
  • Equivalence between batch insertion (insertBatch) and sequential insertion (insert).
  • Empty tree root canonical zero ladder equivalence (computeMerkleZeroLadder).
  • Invariant validation for validateMerkleProof (zero root rejection, length bounds).
  • Fixed regressions: negative and out-of-bounds leaf indices, tree overflow past depth capacity.

Verification

• Ran npx jest test/zk062_fuzz_property.test.ts in sdk:
  • 25 passed across 3 test suites, 0 failures.

Payout Routing

• EVM (Base/Arbitrum/Polygon/ETH): 0xF46C9F6d70C50BF81ef3588AB523a90a594a2F89
• Stellar: GCL6OXAMLD75BMTINA6EMRUDWK5THQUSHMYNLSNBCJAPZJHNYJTUNIBC