# Verkle serialization format in SSZ ```python BandersnatchGroupElement = Bytes32 BandersnatchFieldElement = Bytes32 Stem = Bytes31 MAX_STEMS = 2**16 MAX_COMMITMENTS_PER_STEM = 33 # = 31 for inner nodes + 2 (C1/C2) VERKLE_WIDTH = 256 IPA_PROOF_DEPTH = 8 # = log2(VERKLE_WIDTH) class SuffixStateDiff(Container): suffix: Byte # Null means not currently present current_value: Union[Null, Bytes32] # Null means value not updated new_value: Union[Null, Bytes32] class StemStateDiff(Container): stem: Stem # Valid only if list is sorted by suffixes suffix_diffs: List[SuffixStateDiff, VERKLE_WIDTH] # Valid only if list is sorted by stems StateDiff = List[StemStateDiff, MAX_STEMS] class IpaProof(Container): C_L = Vector[BandersnatchGroupElement, IPA_PROOF_DEPTH] C_R = Vector[BandersnatchGroupElement, IPA_PROOF_DEPTH] final_evaluation = BandersnatchFieldElement class VerkleProof(Container): other_stems: List[Bytes32, MAX_STEMS] depth_extension_present: List[uint8, MAX_STEMS] commitments_by_path: List[BandersnatchGroupElement, MAX_STEMS * MAX_COMMITMENTS_PER_STEM] D: BandersnatchGroupElement ipa_proof: IpaProof class ExecutionWitness(container): state_diff: StateDiff verkle_proof: VerkleProof ``` # Alternative version with bitfields instead of unions ```python BandersnatchGroupElement = Bytes32 BandersnatchFieldElement = Bytes32 Stem = Bytes31 MAX_STEMS = 2**16 MAX_COMMITMENTS_PER_STEM = 33 # = 31 for inner nodes + 2 (C1/C2) VERKLE_WIDTH = 256 IPA_PROOF_DEPTH = 8 # = log2(VERKLE_WIDTH) class SuffixStateDiff(Container): suffix: Byte # Null means not currently present current_value: Union[Null, Bytes32] # Null means value not updated new_value: Union[Null, Bytes32] class StemStateDiff(Container): stem: Stem # Suffixes can be either a list of bytes or a Bitvector # List of bytes MUST be used if <=31 suffixes are present. # The list MUST be sorted starting with the smallest index suffixes: Union[List[Byte, 31], Bitvector[VERKLE_WIDTH]] # Each bit in the bitlist represents one of the suffixes in `suffixes` # 0: The suffix is currently not present/has never been written # 1: The suffix is present. current_values_present: Bitlist[VERKLE_WIDTH] # Values for all the present suffixes current_values: List[Bytes32, VERKLE_WIDTH] # Each bit in the bitlist represents one of the suffixes in `suffixes` # 0: The value for the suffix was not updated # 1: The value for the suffix was updated values_updated: Bitlist[VERKLE_WIDTH] # New values for all suffixes that were updated new_values: List[Bytes32, VERKLE_WIDTH] suffix_diffs: List[SuffixStateDiff, VERKLE_WIDTH] # Valid only if list is sorted by stems StateDiff = List[StemStateDiff, MAX_STEMS] class IpaProof(Container): C_L = Vector[BandersnatchGroupElement, IPA_PROOF_DEPTH] C_R = Vector[BandersnatchGroupElement, IPA_PROOF_DEPTH] final_evaluation = BandersnatchFieldElement class VerkleProof(Container): other_stems: List[Bytes32, MAX_STEMS] depth_extension_present: List[uint8, MAX_STEMS] commitments_by_path: List[BandersnatchGroupElement, MAX_STEMS * MAX_COMMITMENTS_PER_STEM] D: BandersnatchGroupElement ipa_proof: IpaProof class ExecutionWitness(container): state_diff: StateDiff verkle_proof: VerkleProof ```