cycle_scalar represents a member of the cycle curve SCALAR FIELD. This is NOT the native circuit field type. i.e. for a BN254 circuit, cycle_group will be Grumpkin and cycle_scalar will be Grumpkin::ScalarField (BN254 native field is BN254::ScalarField == Grumpkin::BaseField) More...

#include <cycle_scalar.hpp>

Public Types
using	field_t = stdlib::field_t< Builder >

using	Curve = typename Builder::EmbeddedCurve

using	ScalarField = typename Curve::ScalarField

using	BigScalarField = stdlib::bigfield< Builder, typename ScalarField::Params >

Public Member Functions
	cycle_scalar (const field_t &_lo, const field_t &_hi, const size_t bits, const bool skip_primality_test, const bool use_bn254_scalar_field_for_primality_test)

	cycle_scalar (const ScalarField &_in=0)

	cycle_scalar (const field_t &_lo, const field_t &_hi)

	cycle_scalar (const field_t &_in)

bool	is_constant () const

ScalarField	get_value () const

Builder *	get_context () const

size_t	num_bits () const

bool	skip_primality_test () const

bool	use_bn254_scalar_field_for_primality_test () const

void	validate_scalar_is_in_field () const
	Checks that a cycle_scalar value is smaller than a prime field modulus when evaluated over the INTEGERS N.B. The prime we check can be either the SNARK curve group order or the circuit's embedded curve group order (i.e. BN254 or Grumpkin) For a canonical scalar mul, we check against the embedded curve (i.e. the curve cycle_group implements). HOWEVER: for Pedersen hashes and Pedersen commitments, the hashed/committed data will be native circuit field elements i.e. for a BN254 snark, cycle_group = Grumpkin and we will be committing/hashing BN254::ScalarField values NOT Grumpkin::ScalarFIeld values. TLDR: whether the input scalar has to be < BN254::ScalarField or < Grumpkin::ScalarField is context-dependent.

	cycle_scalar (BigScalarField &)
	Construct a new cycle scalar from a bigfield _value, over the same ScalarField Field. If _value is a witness, we add constraints to ensure the conversion is correct by reconstructing a bigfield from the limbs of the cycle_scalar and checking equality with the initial _value.

OriginTag	get_origin_tag () const
	Get the origin tag of the cycle_scalar (a merge of the lo and hi tags)

void	set_origin_tag (const OriginTag &tag) const
	Set the origin tag of lo and hi members of cycle scalar.

void	set_free_witness_tag ()
	Set the free witness flag for the cycle scalar's tags.

void	unset_free_witness_tag ()
	Unset the free witness flag for the cycle scalar's tags.

Static Public Member Functions
static cycle_scalar	from_witness (Builder *context, const ScalarField &value)

static cycle_scalar	from_witness_bitstring (Builder *context, const uint256_t &bitstring, size_t num_bits)
	Use when we want to multiply a group element by a string of bits of known size. N.B. using this constructor method will make our scalar multiplication methods not perform primality tests.

static cycle_scalar	create_from_bn254_scalar (const field_t &_in, bool skip_primality_test=false)
	Use when we want to multiply a group element by a string of bits of known size. N.B. using this constructor method will make our scalar multiplication methods not perform primality tests.

Public Attributes
field_t	lo

field_t	hi

Static Public Attributes
static constexpr size_t	NUM_BITS = ScalarField::modulus.get_msb() + 1

static constexpr size_t	LO_BITS = field_t::native::Params::MAX_BITS_PER_ENDOMORPHISM_SCALAR

static constexpr size_t	HI_BITS = NUM_BITS - LO_BITS

Private Attributes
size_t	_num_bits = NUM_BITS

bool	_skip_primality_test = false

bool	_use_bn254_scalar_field_for_primality_test = false

Detailed Description

template<typename Builder>
class bb::stdlib::cycle_scalar< Builder >

cycle_scalar represents a member of the cycle curve SCALAR FIELD. This is NOT the native circuit field type. i.e. for a BN254 circuit, cycle_group will be Grumpkin and cycle_scalar will be Grumpkin::ScalarField (BN254 native field is BN254::ScalarField == Grumpkin::BaseField)

We convert scalar multiplication inputs into cycle_scalars to enable scalar multiplication to be complete i.e. Grumpkin points multiplied by BN254 scalars does not produce a cyclic group as BN254::ScalarField < Grumpkin::ScalarField This complexity should not leak outside the cycle_group / cycle_scalar implementations, as cycle_scalar performs all required conversions if the input scalars are stdlib::field_t elements

Note: We opted to create a new class to represent cycle_scalar instead of using bigfield, as bigfield is inefficient in this context. All required range checks for cycle_scalar can be obtained for free from the batch_mul algorithm, making the range checks performed by bigfield largely redundant.

Definition at line 34 of file cycle_scalar.hpp.

Member Typedef Documentation

◆ BigScalarField

template<typename Builder >

using bb::stdlib::cycle_scalar< Builder >::BigScalarField = stdlib::bigfield<Builder, typename ScalarField::Params>

Definition at line 39 of file cycle_scalar.hpp.

◆ Curve

template<typename Builder >

using bb::stdlib::cycle_scalar< Builder >::Curve = typename Builder::EmbeddedCurve

Definition at line 37 of file cycle_scalar.hpp.

◆ field_t

template<typename Builder >

using bb::stdlib::cycle_scalar< Builder >::field_t = stdlib::field_t<Builder>

Definition at line 36 of file cycle_scalar.hpp.

◆ ScalarField

template<typename Builder >

using bb::stdlib::cycle_scalar< Builder >::ScalarField = typename Curve::ScalarField

Definition at line 38 of file cycle_scalar.hpp.

Constructor & Destructor Documentation

◆ cycle_scalar() [1/5]

template<typename Builder >

bb::stdlib::cycle_scalar< Builder >::cycle_scalar	(	const field_t &	_lo,
		const field_t &	_hi,
		const size_t	bits,
		const bool	skip_primality_test,
		const bool	use_bn254_scalar_field_for_primality_test
	)

inline

Definition at line 56 of file cycle_scalar.hpp.

◆ cycle_scalar() [2/5]

template<typename Builder >

bb::stdlib::cycle_scalar< Builder >::cycle_scalar ( const ScalarField & _in = 0 )

Definition at line 42 of file cycle_scalar.cpp.

◆ cycle_scalar() [3/5]

template<typename Builder >

bb::stdlib::cycle_scalar< Builder >::cycle_scalar	(	const field_t &	_lo,
		const field_t &	_hi
	)

Definition at line 15 of file cycle_scalar.cpp.

◆ cycle_scalar() [4/5]

template<typename Builder >

bb::stdlib::cycle_scalar< Builder >::cycle_scalar ( const field_t & _in )

Definition at line 20 of file cycle_scalar.cpp.

◆ cycle_scalar() [5/5]

template<typename Builder >

bb::stdlib::cycle_scalar< Builder >::cycle_scalar ( BigScalarField & scalar )

explicit

Construct a new cycle scalar from a bigfield _value, over the same ScalarField Field. If _value is a witness, we add constraints to ensure the conversion is correct by reconstructing a bigfield from the limbs of the cycle_scalar and checking equality with the initial _value.

Template Parameters

Builder

Parameters

_value

Todo:: (https://github.com/AztecProtocol/barretenberg/issues/1016): Optimize this method

Definition at line 130 of file cycle_scalar.cpp.

Member Function Documentation

◆ create_from_bn254_scalar()

template<typename Builder >

cycle_scalar< Builder > bb::stdlib::cycle_scalar< Builder >::create_from_bn254_scalar	(	const field_t &	in,
		bool	skip_primality_test = `false`
	)

static

Use when we want to multiply a group element by a string of bits of known size. N.B. using this constructor method will make our scalar multiplication methods not perform primality tests.

Template Parameters

Builder

Parameters

context
value
num_bits

Returns: cycle_scalar<Builder>

Definition at line 101 of file cycle_scalar.cpp.

◆ from_witness()

template<typename Builder >

cycle_scalar< Builder > bb::stdlib::cycle_scalar< Builder >::from_witness	(	Builder *	context,
		const ScalarField &	value
	)

static

Definition at line 52 of file cycle_scalar.cpp.

◆ from_witness_bitstring()

template<typename Builder >

cycle_scalar< Builder > bb::stdlib::cycle_scalar< Builder >::from_witness_bitstring	(	Builder *	context,
		const uint256_t &	bitstring,
		size_t	num_bits
	)

static

Use when we want to multiply a group element by a string of bits of known size. N.B. using this constructor method will make our scalar multiplication methods not perform primality tests.

Template Parameters

Builder

Parameters

context
value
num_bits

Returns: cycle_scalar<Builder>

Definition at line 75 of file cycle_scalar.cpp.

◆ get_context()

template<typename Builder >

Builder * bb::stdlib::cycle_scalar< Builder >::get_context ( ) const

inline

Definition at line 74 of file cycle_scalar.hpp.

◆ get_origin_tag()

template<typename Builder >

OriginTag bb::stdlib::cycle_scalar< Builder >::get_origin_tag ( ) const

inline

Get the origin tag of the cycle_scalar (a merge of the lo and hi tags)

Returns: OriginTag

Definition at line 89 of file cycle_scalar.hpp.

◆ get_value()

template<typename Builder >

cycle_scalar< Builder >::ScalarField bb::stdlib::cycle_scalar< Builder >::get_value ( ) const

Definition at line 302 of file cycle_scalar.cpp.

◆ is_constant()

template<typename Builder >

bool bb::stdlib::cycle_scalar< Builder >::is_constant ( ) const

Definition at line 248 of file cycle_scalar.cpp.

◆ num_bits()

template<typename Builder >

size_t bb::stdlib::cycle_scalar< Builder >::num_bits ( ) const

inline

Definition at line 75 of file cycle_scalar.hpp.

◆ set_free_witness_tag()

template<typename Builder >

void bb::stdlib::cycle_scalar< Builder >::set_free_witness_tag ( )

inline

Set the free witness flag for the cycle scalar's tags.

Definition at line 103 of file cycle_scalar.hpp.

◆ set_origin_tag()

template<typename Builder >

void bb::stdlib::cycle_scalar< Builder >::set_origin_tag ( const OriginTag & tag ) const

inline

Set the origin tag of lo and hi members of cycle scalar.

Parameters

tag

Definition at line 95 of file cycle_scalar.hpp.

◆ skip_primality_test()

template<typename Builder >

bool bb::stdlib::cycle_scalar< Builder >::skip_primality_test ( ) const

inline

Definition at line 76 of file cycle_scalar.hpp.

◆ unset_free_witness_tag()

template<typename Builder >

void bb::stdlib::cycle_scalar< Builder >::unset_free_witness_tag ( )

inline

Unset the free witness flag for the cycle scalar's tags.

Definition at line 111 of file cycle_scalar.hpp.

◆ use_bn254_scalar_field_for_primality_test()

template<typename Builder >

bool bb::stdlib::cycle_scalar< Builder >::use_bn254_scalar_field_for_primality_test ( ) const

inline

Definition at line 77 of file cycle_scalar.hpp.

◆ validate_scalar_is_in_field()

template<typename Builder >

void bb::stdlib::cycle_scalar< Builder >::validate_scalar_is_in_field ( ) const

Checks that a cycle_scalar value is smaller than a prime field modulus when evaluated over the INTEGERS N.B. The prime we check can be either the SNARK curve group order or the circuit's embedded curve group order (i.e. BN254 or Grumpkin) For a canonical scalar mul, we check against the embedded curve (i.e. the curve cycle_group implements). HOWEVER: for Pedersen hashes and Pedersen commitments, the hashed/committed data will be native circuit field elements i.e. for a BN254 snark, cycle_group = Grumpkin and we will be committing/hashing BN254::ScalarField values NOT Grumpkin::ScalarFIeld values. TLDR: whether the input scalar has to be < BN254::ScalarField or < Grumpkin::ScalarField is context-dependent.

Template Parameters

Builder

Definition at line 266 of file cycle_scalar.cpp.

Member Data Documentation

◆ _num_bits

template<typename Builder >

size_t bb::stdlib::cycle_scalar< Builder >::_num_bits = NUM_BITS

private

Definition at line 49 of file cycle_scalar.hpp.

◆ _skip_primality_test

template<typename Builder >

bool bb::stdlib::cycle_scalar< Builder >::_skip_primality_test = false

private

Definition at line 50 of file cycle_scalar.hpp.

◆ _use_bn254_scalar_field_for_primality_test

template<typename Builder >

bool bb::stdlib::cycle_scalar< Builder >::_use_bn254_scalar_field_for_primality_test = false

private

Definition at line 53 of file cycle_scalar.hpp.

◆ hi

template<typename Builder >

field_t bb::stdlib::cycle_scalar< Builder >::hi

Definition at line 46 of file cycle_scalar.hpp.

◆ HI_BITS

template<typename Builder >

constexpr size_t bb::stdlib::cycle_scalar< Builder >::HI_BITS = NUM_BITS - LO_BITS

staticconstexpr

Definition at line 43 of file cycle_scalar.hpp.

◆ lo

template<typename Builder >

field_t bb::stdlib::cycle_scalar< Builder >::lo

Definition at line 45 of file cycle_scalar.hpp.

◆ LO_BITS

template<typename Builder >

constexpr size_t bb::stdlib::cycle_scalar< Builder >::LO_BITS = field_t::native::Params::MAX_BITS_PER_ENDOMORPHISM_SCALAR

staticconstexpr

Definition at line 42 of file cycle_scalar.hpp.

◆ NUM_BITS

template<typename Builder >

constexpr size_t bb::stdlib::cycle_scalar< Builder >::NUM_BITS = ScalarField::modulus.get_msb() + 1

staticconstexpr

Definition at line 41 of file cycle_scalar.hpp.

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

src/barretenberg/stdlib/primitives/group/cycle_scalar.hpp
src/barretenberg/stdlib/primitives/group/cycle_scalar.cpp

Public Types

Public Member Functions

Static Public Member Functions

Public Attributes

Static Public Attributes

Private Attributes

Detailed Description

Member Typedef Documentation

◆ BigScalarField

◆ Curve

◆ field_t

◆ ScalarField

Constructor & Destructor Documentation

◆ cycle_scalar() [1/5]

◆ cycle_scalar() [2/5]

◆ cycle_scalar() [3/5]

◆ cycle_scalar() [4/5]

◆ cycle_scalar() [5/5]

Member Function Documentation

◆ create_from_bn254_scalar()

◆ from_witness()

◆ from_witness_bitstring()

◆ get_context()

◆ get_origin_tag()

◆ get_value()

◆ is_constant()

◆ num_bits()

◆ set_free_witness_tag()

◆ set_origin_tag()

◆ skip_primality_test()

◆ unset_free_witness_tag()

◆ use_bn254_scalar_field_for_primality_test()

◆ validate_scalar_is_in_field()

Member Data Documentation

◆ _num_bits

◆ _skip_primality_test

◆ _use_bn254_scalar_field_for_primality_test

◆ hi

◆ HI_BITS

◆ lo

◆ LO_BITS

◆ NUM_BITS