Common transcript class for both parties. Stores the data for the current round, as well as the manifest. More...

#include <transcript.hpp>

Inheritance diagram for bb::BaseTranscript< TranscriptParams >:

Public Types
using	DataType = TranscriptParams::DataType

using	Proof = typename TranscriptParams::Proof

Public Member Functions
	BaseTranscript ()

std::vector< DataType >	export_proof ()
	Return the proof data starting at proof_start.

void	load_proof (const std::vector< DataType > &proof)

size_t	size_proof_data ()
	Return the size of proof_data.

void	enable_manifest ()
	Enables the manifest.

template<typename ChallengeType , typename... Strings>
std::array< ChallengeType, sizeof...(Strings)>	get_challenges (const Strings &... labels)
	After all the prover messages have been sent, finalize the round by hashing all the data and then create the number of requested challenges.

template<typename ChallengeType , typename String , std::size_t N>
std::array< ChallengeType, N >	get_challenges (std::array< String, N > const &labels)
	Wrapper around get_challenges to handle array of challenges.

template<typename ChallengeType >
std::vector< ChallengeType >	compute_round_challenge_pows (const size_t num_powers, const ChallengeType &round_challenge)
	Given δ, compute the vector [δ, δ^2,..., δ^2^num_powers].

template<typename ChallengeType , typename String >
std::vector< ChallengeType >	get_powers_of_challenge (const String &label, size_t num_challenges)

template<class T >
void	add_to_independent_hash_buffer (const std::string &label, const T &element)
	Adds an element to an independent hash buffer.

DataType	hash_independent_buffer ()
	Hashes the independent hash buffer and clears it.

template<class T >
void	add_to_hash_buffer (const std::string &label, const T &element)
	Adds an element to the transcript.

template<class T >
void	send_to_verifier (const std::string &label, const T &element)
	Adds a prover message to the transcript, only intended to be used by the prover.

template<class T >
T	receive_from_prover (const std::string &label)
	Reads the next element of type `T` from the transcript, with a predefined label, only used by verifier.

template<typename ChallengeType >
ChallengeType	get_challenge (const std::string &label)

TranscriptManifest	get_manifest () const

void	print ()

BaseTranscript	branch_transcript ()
	Branch a transcript to perform verifier-only computations.

Static Public Member Functions
static DataType	hash (const std::vector< DataType > &data)
	Static hash method that forwards to TranscriptParams hash.

template<typename T >
static std::vector< DataType >	serialize (const T &element)
	Serialize a size_t to a vector of field elements.

static std::shared_ptr< BaseTranscript >	convert_prover_transcript_to_verifier_transcript (const std::shared_ptr< BaseTranscript > &prover_transcript)
	Convert a prover transcript to a verifier transcript.

static std::shared_ptr< BaseTranscript >	prover_init_empty ()
	For testing: initializes transcript with some arbitrary data so that a challenge can be generated after initialization. Only intended to be used by Prover.

static std::shared_ptr< BaseTranscript >	verifier_init_empty (const std::shared_ptr< BaseTranscript > &transcript)
	For testing: initializes transcript based on proof data then receives junk data produced by BaseTranscript::prover_init_empty(). Only intended to be used by Verifier.

Public Attributes
size_t	transcript_index = 0

size_t	round_index = 0

bool	reception_phase = true

std::ptrdiff_t	proof_start = 0

size_t	num_frs_written = 0

size_t	num_frs_read = 0

size_t	round_number = 0

Static Public Attributes
static constexpr bool	in_circuit = InCircuit<DataType>

static constexpr size_t	HASH_OUTPUT_SIZE = 32

Protected Member Functions
void	add_element_frs_to_hash_buffer (const std::string &label, std::span< const DataType > element_frs)
	Adds challenge elements to the current_round_buffer and updates the manifest.

template<typename T >
void	serialize_to_buffer (const T &element, Proof &proof_data)
	Serializes object and appends it to proof_data.

template<typename T >
T	deserialize_from_buffer (const Proof &proof_data, size_t &offset) const
	Deserializes the frs starting at offset into the typed element and returns that element.

Protected Attributes
Proof	proof_data

Private Member Functions
std::array< DataType, 2 >	get_next_duplex_challenge_buffer (size_t num_challenges)
	Compute next challenge c_next = H( Compress(c_prev \|\| round_buffer) )

Private Attributes
bool	is_first_challenge = true

DataType	previous_challenge {}

std::vector< DataType >	current_round_data

std::vector< DataType >	independent_hash_buffer

bool	use_manifest = false

TranscriptManifest	manifest

Detailed Description

template<typename TranscriptParams>
class bb::BaseTranscript< TranscriptParams >

Common transcript class for both parties. Stores the data for the current round, as well as the manifest.

Definition at line 154 of file transcript.hpp.

Member Typedef Documentation

◆ DataType

template<typename TranscriptParams >

using bb::BaseTranscript< TranscriptParams >::DataType = TranscriptParams::DataType

Definition at line 156 of file transcript.hpp.

◆ Proof

template<typename TranscriptParams >

using bb::BaseTranscript< TranscriptParams >::Proof = typename TranscriptParams::Proof

Definition at line 157 of file transcript.hpp.

Constructor & Destructor Documentation

◆ BaseTranscript()

template<typename TranscriptParams >

bb::BaseTranscript< TranscriptParams >::BaseTranscript ( )

inline

Definition at line 172 of file transcript.hpp.

Member Function Documentation

◆ add_element_frs_to_hash_buffer()

template<typename TranscriptParams >

void bb::BaseTranscript< TranscriptParams >::add_element_frs_to_hash_buffer	(	const std::string &	label,
		std::span< const DataType >	element_frs
	)

inlineprotected

Adds challenge elements to the current_round_buffer and updates the manifest.

Parameters

label	of the element sent
element_frs	serialized

Definition at line 257 of file transcript.hpp.

◆ add_to_hash_buffer()

template<typename TranscriptParams >

template<class T >

void bb::BaseTranscript< TranscriptParams >::add_to_hash_buffer	(	const std::string &	label,
		const T &	element
	)

inline

Adds an element to the transcript.

Serializes the element to frs and adds it to the current_round_data buffer. Does NOT add the element to the proof.

Parameters

label	Human-readable name for the challenge.
element	Element to be added.

Definition at line 506 of file transcript.hpp.

◆ add_to_independent_hash_buffer()

template<typename TranscriptParams >

template<class T >

void bb::BaseTranscript< TranscriptParams >::add_to_independent_hash_buffer	(	const std::string &	label,
		const T &	element
	)

inline

Adds an element to an independent hash buffer.

Serializes the element to frs and adds it to the independent hash buffer. Does NOT add the element to the proof.

Parameters

label	Human-readable name for the challenge.
element	Element to be added.

Definition at line 455 of file transcript.hpp.

◆ branch_transcript()

template<typename TranscriptParams >

BaseTranscript bb::BaseTranscript< TranscriptParams >::branch_transcript ( )

inline

Branch a transcript to perform verifier-only computations.

This function takes the current state of a transcript and creates a new transcript that starts from that state. In this way, computations that are not part of the prover's transcript (e.g., computations that can be used to perform calculations more efficiently) will not affect the verifier's transcript.

If transcript = (.., previous_challenge), then for soundness it is enough that branched_transcript = (previous_challenge, ...) However, there are a few implementation details we need to take into account:

branched_transcript will interact with witnesses that come from transcript. To prevent the tool that detects FS bugs from raising an error, we must ensure that branched_transcript.transcript_index = transcript.transcript_index.
To aid debugging, we set branched_transcript.round_index = transcript.round_index, so that it is clear that branched_transcript builds on the current state of transcript.
To aid debugging, we increase transcript.round_index by BRANCHING_JUMP, so that there is a gap between what happens before and after the transcript is branched.
To ensure soundness: a. We add to the hash buffer of branched_transcript the value transcript.previous_challenge b. We enforce ASSERT(current_round_data.empty())

Note: We could remove 4.b and add to the hash buffer of branched_transcript both transcript.previous_challenge and transcript.current_round_data. However, this would conflict with 3 (as the round in transcript is not finished yet). There seems to be no reason why the branching cannot happen after the round is concluded, so we choose this implementation.

The relation between the transcript and the branched transcript is the following:

round_index transcript branched_transcript 0 * 1 | | | | | n * ================= *

n+BRANCHING_JUMP * | n+6 | | | | | ... ... ...

Returns: BaseTranscript

Definition at line 739 of file transcript.hpp.

◆ compute_round_challenge_pows()

template<typename TranscriptParams >

template<typename ChallengeType >

std::vector< ChallengeType > bb::BaseTranscript< TranscriptParams >::compute_round_challenge_pows	(	const size_t	num_powers,
		const ChallengeType &	round_challenge
	)

inline

Given δ, compute the vector [δ, δ^2,..., δ^2^num_powers].

This is Step 2 of the protocol as written in the paper.

Definition at line 430 of file transcript.hpp.

◆ convert_prover_transcript_to_verifier_transcript()

template<typename TranscriptParams >

static std::shared_ptr< BaseTranscript > bb::BaseTranscript< TranscriptParams >::convert_prover_transcript_to_verifier_transcript ( const std::shared_ptr< BaseTranscript< TranscriptParams > > & prover_transcript )

inlinestatic

Convert a prover transcript to a verifier transcript.

Parameters

prover_transcript The prover transcript to convert

Returns: std::shared_ptr<BaseTranscript> The verifier transcript

Definition at line 637 of file transcript.hpp.

◆ deserialize_from_buffer()

template<typename TranscriptParams >

template<typename T >

T bb::BaseTranscript< TranscriptParams >::deserialize_from_buffer	(	const Proof &	proof_data,
		size_t &	offset
	)		const

inlineprotected

Deserializes the frs starting at offset into the typed element and returns that element.

Using the template parameter and the offset argument, this function deserializes the frs with from_buffer and then increments the offset appropriately based on the number of frs that were deserialized.

Template Parameters

T

Parameters

proof_data
offset

Returns: T

Definition at line 289 of file transcript.hpp.

◆ enable_manifest()

template<typename TranscriptParams >

void bb::BaseTranscript< TranscriptParams >::enable_manifest ( )

inline

Enables the manifest.

Definition at line 335 of file transcript.hpp.

◆ export_proof()

template<typename TranscriptParams >

std::vector< DataType > bb::BaseTranscript< TranscriptParams >::export_proof ( )

inline

Return the proof data starting at proof_start.

This function returns the elements of the transcript in the interval [proof_start : proof_start + num_frs_written] and then updates proof_start. It is useful for when two provers share a transcript, as calling export_proof at the end of each provers' code returns the slices T_1, T_2 of the transcript that must be loaded by the verifiers via load_proof.

Definition at line 310 of file transcript.hpp.

◆ get_challenge()

template<typename TranscriptParams >

template<typename ChallengeType >

ChallengeType bb::BaseTranscript< TranscriptParams >::get_challenge ( const std::string & label )

inline

Definition at line 676 of file transcript.hpp.

◆ get_challenges() [1/2]

template<typename TranscriptParams >

template<typename ChallengeType , typename... Strings>

std::array< ChallengeType, sizeof...(Strings)> bb::BaseTranscript< TranscriptParams >::get_challenges ( const Strings &... labels )

inline

After all the prover messages have been sent, finalize the round by hashing all the data and then create the number of requested challenges.

Challenges are generated by iteratively hashing over the previous challenge, using get_next_challenge_buffer(). Note that the pairs of challenges will be 128 and 126 bits, as in they will be [128, 126, 128, 126, ...].

Parameters

labels human-readable names for the challenges for the manifest

Returns: std::array<Fr, num_challenges> challenges for this round.

Definition at line 369 of file transcript.hpp.

◆ get_challenges() [2/2]

template<typename TranscriptParams >

template<typename ChallengeType , typename String , std::size_t N>

std::array< ChallengeType, N > bb::BaseTranscript< TranscriptParams >::get_challenges ( std::array< String, N > const & labels )

inline

Wrapper around get_challenges to handle array of challenges.

Parameters

array of labels human-readable names for the challenges for the manifest

Returns: std::array<ChallengeType, N> challenges for this round.

Definition at line 419 of file transcript.hpp.

◆ get_manifest()

template<typename TranscriptParams >

TranscriptManifest bb::BaseTranscript< TranscriptParams >::get_manifest ( ) const

inline

Definition at line 686 of file transcript.hpp.

◆ get_next_duplex_challenge_buffer()

template<typename TranscriptParams >

std::array< DataType, 2 > bb::BaseTranscript< TranscriptParams >::get_next_duplex_challenge_buffer ( size_t num_challenges )

inlineprivate

Compute next challenge c_next = H( Compress(c_prev || round_buffer) )

This function computes a new challenge for the current round using the previous challenge and the current round data, if they exist. It clears the current_round_data if nonempty after computing the challenge to minimize how much we compress. It also sets previous_challenge to the current challenge buffer to set up next function call.

Returns: std::array<Fr, HASH_OUTPUT_SIZE>

Definition at line 208 of file transcript.hpp.

◆ get_powers_of_challenge()

template<typename TranscriptParams >

template<typename ChallengeType , typename String >

std::vector< ChallengeType > bb::BaseTranscript< TranscriptParams >::get_powers_of_challenge	(	const String &	label,
		size_t	num_challenges
	)

inline

Definition at line 442 of file transcript.hpp.

◆ hash()

template<typename TranscriptParams >

static DataType bb::BaseTranscript< TranscriptParams >::hash ( const std::vector< DataType > & data )

inlinestatic

Static hash method that forwards to TranscriptParams hash.

This method allows hash to be called on the Transcript class directly, which is needed for verification key hashing.

Parameters

data	Vector of field elements to hash

Returns: Fr Hash result

Definition at line 345 of file transcript.hpp.

◆ hash_independent_buffer()

template<typename TranscriptParams >

DataType bb::BaseTranscript< TranscriptParams >::hash_independent_buffer ( )

inline

Hashes the independent hash buffer and clears it.

Returns: Fr The hash of the independent hash buffer.

Definition at line 491 of file transcript.hpp.

◆ load_proof()

template<typename TranscriptParams >

void bb::BaseTranscript< TranscriptParams >::load_proof ( const std::vector< DataType > & proof )

inline

Definition at line 319 of file transcript.hpp.

◆ print()

template<typename TranscriptParams >

void bb::BaseTranscript< TranscriptParams >::print ( )

inline

Definition at line 688 of file transcript.hpp.

◆ prover_init_empty()

template<typename TranscriptParams >

static std::shared_ptr< BaseTranscript > bb::BaseTranscript< TranscriptParams >::prover_init_empty ( )

inlinestatic

For testing: initializes transcript with some arbitrary data so that a challenge can be generated after initialization. Only intended to be used by Prover.

Returns: BaseTranscript

Definition at line 653 of file transcript.hpp.

◆ receive_from_prover()

template<typename TranscriptParams >

template<class T >

T bb::BaseTranscript< TranscriptParams >::receive_from_prover ( const std::string & label )

inline

Reads the next element of type T from the transcript, with a predefined label, only used by verifier.

Parameters

label Human readable name for the challenge.

Returns: deserialized element of type T

Definition at line 591 of file transcript.hpp.

◆ send_to_verifier()

template<typename TranscriptParams >

template<class T >

void bb::BaseTranscript< TranscriptParams >::send_to_verifier	(	const std::string &	label,
		const T &	element
	)

inline

Adds a prover message to the transcript, only intended to be used by the prover.

Serializes the provided object into proof_data, and updates the current round state in add_element_frs_to_hash_buffer.

Parameters

label	Description/name of the object being added.
element	Serializable object that will be added to the transcript

Todo:: Use a concept to only allow certain types to be passed. Requirements are that the object should be serializable.

Definition at line 550 of file transcript.hpp.

◆ serialize()

template<typename TranscriptParams >

template<typename T >

static std::vector< DataType > bb::BaseTranscript< TranscriptParams >::serialize ( const T & element )

inlinestatic

Serialize a size_t to a vector of field elements.

Parameters

element

Returns: std::vector<DataType>

Definition at line 353 of file transcript.hpp.

◆ serialize_to_buffer()

template<typename TranscriptParams >

template<typename T >

void bb::BaseTranscript< TranscriptParams >::serialize_to_buffer	(	const T &	element,
		Proof &	proof_data
	)

inlineprotected

Serializes object and appends it to proof_data.

Calls to_buffer on element to serialize, and modifies proof_data object by appending the serialized frs to it.

Template Parameters

T

Parameters

element
proof_data

Definition at line 275 of file transcript.hpp.

◆ size_proof_data()

template<typename TranscriptParams >

size_t bb::BaseTranscript< TranscriptParams >::size_proof_data ( )

inline

Return the size of proof_data.

Returns: size_t

Definition at line 329 of file transcript.hpp.

◆ verifier_init_empty()

template<typename TranscriptParams >

static std::shared_ptr< BaseTranscript > bb::BaseTranscript< TranscriptParams >::verifier_init_empty ( const std::shared_ptr< BaseTranscript< TranscriptParams > > & transcript )

inlinestatic

For testing: initializes transcript based on proof data then receives junk data produced by BaseTranscript::prover_init_empty(). Only intended to be used by Verifier.

Parameters

transcript

Returns: BaseTranscript

Definition at line 668 of file transcript.hpp.

Member Data Documentation

◆ current_round_data

template<typename TranscriptParams >

std::vector<DataType> bb::BaseTranscript< TranscriptParams >::current_round_data

private

Definition at line 191 of file transcript.hpp.

◆ HASH_OUTPUT_SIZE

template<typename TranscriptParams >

constexpr size_t bb::BaseTranscript< TranscriptParams >::HASH_OUTPUT_SIZE = 32

staticconstexpr

Definition at line 180 of file transcript.hpp.

◆ in_circuit

template<typename TranscriptParams >

constexpr bool bb::BaseTranscript< TranscriptParams >::in_circuit = InCircuit<DataType>

staticconstexpr

Definition at line 160 of file transcript.hpp.

◆ independent_hash_buffer

template<typename TranscriptParams >

std::vector<DataType> bb::BaseTranscript< TranscriptParams >::independent_hash_buffer

private

Definition at line 193 of file transcript.hpp.

◆ is_first_challenge

template<typename TranscriptParams >

bool bb::BaseTranscript< TranscriptParams >::is_first_challenge = true

private

Definition at line 188 of file transcript.hpp.

◆ manifest

template<typename TranscriptParams >

TranscriptManifest bb::BaseTranscript< TranscriptParams >::manifest

private

Definition at line 198 of file transcript.hpp.

◆ num_frs_read

template<typename TranscriptParams >

size_t bb::BaseTranscript< TranscriptParams >::num_frs_read = 0

Definition at line 184 of file transcript.hpp.

◆ num_frs_written

template<typename TranscriptParams >

size_t bb::BaseTranscript< TranscriptParams >::num_frs_written = 0

Definition at line 183 of file transcript.hpp.

◆ previous_challenge

template<typename TranscriptParams >

DataType bb::BaseTranscript< TranscriptParams >::previous_challenge {}

private

Definition at line 189 of file transcript.hpp.

◆ proof_data

template<typename TranscriptParams >

Proof bb::BaseTranscript< TranscriptParams >::proof_data

protected

Definition at line 249 of file transcript.hpp.

◆ proof_start

template<typename TranscriptParams >

std::ptrdiff_t bb::BaseTranscript< TranscriptParams >::proof_start = 0

Definition at line 182 of file transcript.hpp.

◆ reception_phase

template<typename TranscriptParams >

bool bb::BaseTranscript< TranscriptParams >::reception_phase = true

Definition at line 170 of file transcript.hpp.

◆ round_index

template<typename TranscriptParams >

size_t bb::BaseTranscript< TranscriptParams >::round_index = 0

Definition at line 167 of file transcript.hpp.

◆ round_number

template<typename TranscriptParams >

size_t bb::BaseTranscript< TranscriptParams >::round_number = 0

Definition at line 185 of file transcript.hpp.

◆ transcript_index

template<typename TranscriptParams >

size_t bb::BaseTranscript< TranscriptParams >::transcript_index = 0

Definition at line 163 of file transcript.hpp.

◆ use_manifest

template<typename TranscriptParams >

bool bb::BaseTranscript< TranscriptParams >::use_manifest = false

private

Definition at line 195 of file transcript.hpp.

The documentation for this class was generated from the following file:

src/barretenberg/transcript/transcript.hpp

Public Types

Public Member Functions

Static Public Member Functions

Public Attributes

Static Public Attributes

Protected Member Functions

Protected Attributes

Private Member Functions

Private Attributes

Detailed Description

Member Typedef Documentation

◆ DataType

◆ Proof

Constructor & Destructor Documentation

◆ BaseTranscript()

Member Function Documentation

◆ add_element_frs_to_hash_buffer()

◆ add_to_hash_buffer()

◆ add_to_independent_hash_buffer()

◆ branch_transcript()

◆ compute_round_challenge_pows()

◆ convert_prover_transcript_to_verifier_transcript()

◆ deserialize_from_buffer()

◆ enable_manifest()

◆ export_proof()

◆ get_challenge()

◆ get_challenges() [1/2]

◆ get_challenges() [2/2]

◆ get_manifest()

◆ get_next_duplex_challenge_buffer()

◆ get_powers_of_challenge()

◆ hash()

◆ hash_independent_buffer()

◆ load_proof()

◆ print()

◆ prover_init_empty()

◆ receive_from_prover()

◆ send_to_verifier()

◆ serialize()

◆ serialize_to_buffer()

◆ size_proof_data()

◆ verifier_init_empty()

Member Data Documentation

◆ current_round_data

◆ HASH_OUTPUT_SIZE

◆ in_circuit

◆ independent_hash_buffer

◆ is_first_challenge

◆ manifest

◆ num_frs_read

◆ num_frs_written

◆ previous_challenge

◆ proof_data

◆ proof_start

◆ reception_phase

◆ round_index

◆ round_number

◆ transcript_index

◆ use_manifest