org.bouncycastle.crypto.hash2curve

Class HashToEllipticCurve

java.lang.Object

org.bouncycastle.crypto.hash2curve.HashToEllipticCurve

public class HashToEllipticCurve
extends java.lang.Object

Main class for implementing hash to elliptic curve according to RFC 9380

Steps: 1. u = hash_to_field(msg, 2) 2. Q0 = map_to_curve(u[0]) 3. Q1 = map_to_curve(u[1]) 4. R = Q0 + Q1 # Point addition 5. P = clear_cofactor(R) 6. return P

Field Summary

Fields

Modifier and Type	Field and Description
protected CurveProcessor	curveProcessor
protected HashToField	hashToField
protected MapToCurve	mapToCurve

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	HashToEllipticCurve(HashToField hashToField, MapToCurve mapToCurve, CurveProcessor curveProcessor)

Method Summary

Modifier and Type	Method and Description
ECPoint	encodeToCurve(byte[] message) Encode a message to an elliptic curve point using the RFC 9380 encode_to_curve function.
AffineXY	getAffineXY(ECPoint point) Converts an elliptic-curve point into the affine (x, y) coordinate representation defined by the hash-to-curve suite.
static HashToEllipticCurve	getInstance(HashToCurveProfile profile, java.lang.String dst)
ECPoint	hashToCurve(byte[] message) Hashes a message to an elliptic curve point using the RFC 9380 hash_to_curve function.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

hashToField

protected final HashToField hashToField

mapToCurve

protected final MapToCurve mapToCurve

curveProcessor

protected final CurveProcessor curveProcessor

Constructor Detail

HashToEllipticCurve

protected HashToEllipticCurve(HashToField hashToField,
                              MapToCurve mapToCurve,
                              CurveProcessor curveProcessor)

Method Detail

getInstance

public static HashToEllipticCurve getInstance(HashToCurveProfile profile,
                                              java.lang.String dst)

hashToCurve

public ECPoint hashToCurve(byte[] message)

Hashes a message to an elliptic curve point using the RFC 9380 hash_to_curve function. This function provides a uniform distribution of resulting points.

Parameters:

message - the message to be hashed

Returns:

the resulting elliptic curve point P

encodeToCurve

public ECPoint encodeToCurve(byte[] message)

Encode a message to an elliptic curve point using the RFC 9380 encode_to_curve function. This function does not provide a uniform distribution of resulting points. This function MUST NOT be used when uniform distribution is a security requirement.

Parameters:

message - the message to be hashed

Returns:

the resulting elliptic curve point P

getAffineXY

public AffineXY getAffineXY(ECPoint point)

Converts an elliptic-curve point into the affine (x, y) coordinate representation defined by the hash-to-curve suite.

The returned coordinates are intended for serialization, testing, and interoperability with the reference outputs defined in RFC 9380. For most Weierstrass curves, this is simply the affine (x, y) coordinates of the given point. For curves that use a different coordinate model in the specification (e.g. Montgomery curves such as curve25519), this method applies the appropriate coordinate transformation.

This method does not change the underlying group element represented by the point. It only changes how that point is expressed as field elements. The input point is expected to be a valid point on the curve used by the implementation.

Parameters:

point - point on the chosen ECCurve for the selected hash2Curve profile

Returns:

AffineXY coordinates for the point on the curve defined in RFC 9380 for the selected profile