A scalar modulo the curve order. More...

#include <point_255.hxx>

Inheritance diagram for decaf::Ristretto::Scalar:

Public Types
typedef decaf_255_scalar_t	Wrapped
	wrapped C type

Public Member Functions
	Scalar (uint64_t w) DECAF_NOEXCEPT
	Set to an unsigned word.

	Scalar (int64_t w) DECAF_NOEXCEPT
	Set to a signed word.

	Scalar (unsigned int w) DECAF_NOEXCEPT
	Set to an unsigned word.

	Scalar (int w) DECAF_NOEXCEPT
	Set to a signed word.

	Scalar (Rng &rng) DECAF_NOEXCEPT
	Construct from RNG.

	Scalar (const Wrapped &t=decaf_255_scalar_zero) DECAF_NOEXCEPT
	Construct from decaf_scalar_t object.

	Scalar (const Scalar &x) DECAF_NOEXCEPT
	Copy constructor.

	Scalar (const Block &buffer) DECAF_NOEXCEPT
	Construct from arbitrary-length little-endian byte sequence.

size_t	ser_size () const DECAF_NOEXCEPT
	Serializable instance.

void	serialize_into (unsigned char *buffer) const DECAF_NOEXCEPT
	Serializable instance.

Scalar &	operator= (const Scalar &x) DECAF_NOEXCEPT
	Assignment.

Scalar &	operator= (uint64_t w) DECAF_NOEXCEPT
	Assign from unsigned 64-bit integer.

Scalar &	operator= (int64_t w) DECAF_NOEXCEPT
	Assign from signed int.

Scalar &	operator= (unsigned int w) DECAF_NOEXCEPT
	Assign from unsigned int.

Scalar &	operator= (int w) DECAF_NOEXCEPT
	Assign from signed int.

	~Scalar () DECAF_NOEXCEPT
	Destructor securely zeorizes the scalar.

Scalar &	operator= (const Block &bl) DECAF_NOEXCEPT
	Assign from arbitrary-length little-endian byte sequence in a Block.

Scalar	operator+ (const Scalar &q) const DECAF_NOEXCEPT
	Add.

Scalar &	operator+= (const Scalar &q) DECAF_NOEXCEPT
	Add to this.

Scalar	operator- (const Scalar &q) const DECAF_NOEXCEPT
	Subtract.

Scalar &	operator-= (const Scalar &q) DECAF_NOEXCEPT
	Subtract from this.

Scalar	operator* (const Scalar &q) const DECAF_NOEXCEPT
	Multiply.

Scalar &	*operator=** (const Scalar &q) DECAF_NOEXCEPT
	Multiply into this.

Scalar	operator- () const DECAF_NOEXCEPT
	Negate.

Scalar	inverse () const
	Return 1/this.

decaf_error_t DECAF_WARN_UNUSED	inverse_noexcept (Scalar &r) const DECAF_NOEXCEPT
	Invert with Fermat's Little Theorem (slow!).

Scalar	operator/ (const Scalar &q) const
	Return this/q.

Scalar &	operator/= (const Scalar &q)
	Set this to this/q.

Scalar	half () const
	Return half this scalar.

bool	operator!= (const Scalar &q) const DECAF_NOEXCEPT
	Compare in constant time.

bool	operator== (const Scalar &q) const DECAF_NOEXCEPT
	Compare in constant time.

Point	operator* (const Point &q) const DECAF_NOEXCEPT
	Scalarmul with scalar on left.

Point	operator* (const Precomputed &q) const DECAF_NOEXCEPT
	Scalarmul-precomputed with scalar on left.

SecureBuffer	direct_scalarmul (const FixedBlock< SER_BYTES > &in, decaf_bool_t allow_identity=DECAF_FALSE, decaf_bool_t short_circuit=DECAF_TRUE) const
	Direct scalar multiplication.

decaf_error_t DECAF_WARN_UNUSED	direct_scalarmul_noexcept (FixedBuffer< SER_BYTES > &out, const FixedBlock< SER_BYTES > &in, decaf_bool_t allow_identity=DECAF_FALSE, decaf_bool_t short_circuit=DECAF_TRUE) const DECAF_NOEXCEPT
	Direct scalar multiplication.

Public Member Functions inherited from decaf::Serializable< Scalar >
size_t	ser_size () const DECAF_NOEXCEPT
	Return the number of bytes needed to serialize this object.

void	serialize_into (unsigned char *buf) const DECAF_NOEXCEPT
	Serialize this object into a buffer.

SecureBuffer	serialize () const
	Serialize this object into a SecureBuffer and return it.

Static Public Member Functions
static decaf_error_t DECAF_WARN_UNUSED	decode (Scalar &sc, const FixedBlock< SER_BYTES > buffer) DECAF_NOEXCEPT
	Decode from correct-length little-endian byte sequence.

Public Attributes
Wrapped	s
	access to the underlying scalar object

Static Public Attributes
static const size_t	SER_BYTES = DECAF_255_SCALAR_BYTES
	Size of a serialized element.

Detailed Description

A scalar modulo the curve order.

Supports the usual arithmetic operations, all in constant time.

Member Function Documentation

◆ decode()

static decaf_error_t DECAF_WARN_UNUSED decaf::Ristretto::Scalar::decode	(	Scalar &	sc,
		const FixedBlock< SER_BYTES >	buffer
	)

inlinestatic

Decode from correct-length little-endian byte sequence.

Returns: DECAF_FAILURE if the scalar is greater than or equal to the group order q.

◆ direct_scalarmul()

SecureBuffer decaf::Ristretto::Scalar::direct_scalarmul	(	const FixedBlock< SER_BYTES > &	in,
		decaf_bool_t	allow_identity = `DECAF_FALSE`,
		decaf_bool_t	short_circuit = `DECAF_TRUE`
	)		const

inline

Direct scalar multiplication.

Exceptions

CryptoException if the input didn't decode.

◆ half()

Scalar decaf::Ristretto::Scalar::half ( ) const

inline

Return half this scalar.

Much faster than /2.

◆ inverse()

Scalar decaf::Ristretto::Scalar::inverse ( ) const

inline

Return 1/this.

Exceptions

CryptoException if this is 0.

◆ inverse_noexcept()

decaf_error_t DECAF_WARN_UNUSED decaf::Ristretto::Scalar::inverse_noexcept ( Scalar & r ) const

inline

Invert with Fermat's Little Theorem (slow!).

If *this == 0, set r=0 and return DECAF_FAILURE.

◆ operator/()

Scalar decaf::Ristretto::Scalar::operator/ ( const Scalar & q ) const

inline

Return this/q.

Exceptions

CryptoException if q == 0.

◆ operator/=()

Scalar & decaf::Ristretto::Scalar::operator/= ( const Scalar & q )

inline

Set this to this/q.

Exceptions

CryptoException if q == 0.

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

src/GENERATED/include/decaf/point_255.hxx

Public Types

Public Member Functions

Static Public Member Functions

Public Attributes

Static Public Attributes

Detailed Description

Member Function Documentation

◆ decode()

◆ direct_scalarmul()

◆ half()

◆ inverse()

◆ inverse_noexcept()

◆ operator/()

◆ operator/=()