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removing stdlib hashing for now
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@ledwards2225
ledwards2225 committed Jul 28, 2023
1 parent ec26e4b commit c63dbe2
Showing 1 changed file with 34 additions and 81 deletions.
115 changes: 34 additions & 81 deletions ...uits/cpp/barretenberg/cpp/src/barretenberg/stdlib/recursion/transcript/honk_trancript.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -34,75 +34,64 @@ template <typename Builder> class Transcript {

VerifierTranscript native_transcript;
Builder* builder;
// maximum number of bytes we can store in a field element w/o wrapping modulus is 31.
// while we could store more *bits*, we want `preimage_buffer` to mirror how data is formatted
// when we serialize field/group elements natively (i.e. a byte array)
static constexpr size_t NUM_BITS_PER_PREIMAGE_ELEMENT = 31UL * 8UL;
PedersenPreimageBuilder<Builder, NUM_BITS_PER_PREIMAGE_ELEMENT> preimage_buffer;

Transcript(Builder* builder, auto proof_data)
: native_transcript(proof_data)
, builder(builder)
, preimage_buffer(builder){};
, builder(builder){};

/**
* @brief Get the underlying native transcript manifest (primarily for debugging)
*
*
*/
auto get_manifest() const { return native_transcript.get_manifest(); };

/**
* @brief Compute the challenges (more than 1) indicated by labels
*
* @tparam Strings
*
* @tparam Strings
* @param labels Names of the challenges to be computed
* @return std::array<FF, sizeof...(Strings)> Array of challenges
*/
template <typename... Strings> std::array<FF, sizeof...(Strings)> get_challenges(const Strings&... labels)
template <typename... Strings> std::array<field_pt, sizeof...(Strings)> get_challenges(const Strings&... labels)
{
// Compute the indicated challenges from the native transcript
constexpr size_t num_challenges = sizeof...(Strings);
std::array<FF, num_challenges> challenges{};
challenges = native_transcript.get_challenges(labels...);

// Do stdlib version of fiat-shamir here..
std::array<FF, num_challenges> native_challenges{};
native_challenges = native_transcript.get_challenges(labels...);

/*
* TODO(luke): Do stdlib hashing here. E.g., for the current pedersen/blake setup, we could write data into a
* byte_array as it is received from prover, then compress via pedersen and apply blake3s. Not doing this now
* since it's a pain and we'll be revamping our hashing anyway. For now, simply convert the native hashes to
* stdlib types without adding any hashing constraints.
*/
std::array<field_pt, num_challenges> challenges;
for (size_t i = 0; i < num_challenges; ++i) {
challenges[i] = native_challenges[i];
}

return challenges;
}

/**
* @brief Compute the single challenge indicated by the input label
*
*
* @param label Name of challenge
* @return FF Challenge
* @return field_pt Challenge
*/
field_pt get_challenge(const std::string& label)
{
// Compute the indicated challenge from the native transcript
// WORKTODO: need to call this to update native transcript but maybe dont need the native challenge itself
[[maybe_unused]] auto native_challenge = native_transcript.get_challenge(label);

// Stdlib Fiat-Shamir
// Compress buffer via pedersen then hash the result using Blake3s
field_pt compressed_buffer = preimage_buffer.compress(0);
auto buffer_bytes = byte_array(compressed_buffer);
auto challenge_buffer = blake3s(buffer_bytes);

auto current_challenge = field_pt(challenge_buffer.slice(0, HASH_OUTPUT_SIZE));

info("native_challenge = ", native_challenge);
info("current_challenge = ", current_challenge.get_value());
auto native_challenge = native_transcript.get_challenge(label);

// TODO(luke): Stdlib hashing here...

preimage_buffer.clear();
preimage_buffer.add_element(current_challenge);

return current_challenge;
return field_pt(native_challenge);
}

/**
* @brief Extract a native element from the transcript and return a corresponding stdlib type
*
*
* @tparam T Type of the native element to be extracted
* @param label Name of the element
* @return The corresponding element of appropriate stdlib type
Expand All @@ -118,77 +107,41 @@ template <typename Builder> class Transcript {

/**
* @brief Construct stdlib field from uint32_t
*
* @param element
* @return field_pt
*
* @param element
* @return field_pt
*/
field_pt stdlib_type_from_witness(uint32_t native_element)
{
auto element = witness_pt(builder, native_element);

// WORKTODO: do something special here for the uint32_t?
preimage_buffer.add_element(element);

return element;
}

/**
* @brief Construct stdlib field from native field type
*
* @param native_element
* @return field_pt
*
* @param native_element
* @return field_pt
*/
field_pt stdlib_type_from_witness(FF native_element)
{
auto element = witness_pt(builder, native_element);

preimage_buffer.add_element(element);

return element;
}

/**
* @brief Construct stdlib group from native affine group element type
*
* @param native_element
* @return field_pt
*
* @param native_element
* @return field_pt
*/
group_pt stdlib_type_from_witness(Commitment native_element)
{
auto element = group_pt::from_witness(builder, native_element);

add_commitment_to_preimage_buffer(element);

return element;
}

/**
* @brief Add an EC point / commitment to the pedersen preimage buffer
*
* @param point
*/
void add_commitment_to_preimage_buffer(group_pt& point)
{
const auto& x = point.x;
const auto& y = point.y;
constexpr size_t last_limb_bits = 256 - (fq_pt::NUM_LIMB_BITS * 3);
preimage_buffer.add_element_with_existing_range_constraint(y.binary_basis_limbs[3].element,
last_limb_bits);
preimage_buffer.add_element_with_existing_range_constraint(y.binary_basis_limbs[2].element,
fq_pt::NUM_LIMB_BITS);
preimage_buffer.add_element_with_existing_range_constraint(y.binary_basis_limbs[1].element,
fq_pt::NUM_LIMB_BITS);
preimage_buffer.add_element_with_existing_range_constraint(y.binary_basis_limbs[0].element,
fq_pt::NUM_LIMB_BITS);
preimage_buffer.add_element_with_existing_range_constraint(x.binary_basis_limbs[3].element,
last_limb_bits);
preimage_buffer.add_element_with_existing_range_constraint(x.binary_basis_limbs[2].element,
fq_pt::NUM_LIMB_BITS);
preimage_buffer.add_element_with_existing_range_constraint(x.binary_basis_limbs[1].element,
fq_pt::NUM_LIMB_BITS);
preimage_buffer.add_element_with_existing_range_constraint(x.binary_basis_limbs[0].element,
fq_pt::NUM_LIMB_BITS);
return element;
}

};
} // namespace proof_system::plonk::stdlib::recursion::honk

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