Class SM9P256V1Field

java.lang.Object

org.bouncycastle.math.ec.custom.gm.SM9P256V1Field

public class SM9P256V1Field
extends Object

Prime-field arithmetic for the SM9 256-bit Barreto-Naehrig base field F_q (GM/T 0044.5-2016), used by the G1 curve SM9P256V1Curve.

Unlike SM2P256V1Field (whose sparse prime admits a fast Solinas reduction and stores elements in the ordinary residue representation), the SM9 BN prime is a general 256-bit prime, so this field keeps elements in Montgomery form (a·R mod q, R = 2^256) and multiplies with a Montgomery (SOS) reduction. Fixed-limb Nat256 arithmetic makes the field operations constant time (no data-dependent branches beyond the standard conditional subtractions), unlike the variable-length BigInteger the generic ECCurve.Fp would use.

The constants n0 = -q^-1 mod 2^32 and R^2 mod q are derived from q at class load (a micro-optimisation would inline them as int[] literals as SM2 does).

Method Summary

Modifier and Type	Method	Description
static void	add(int[] x, int[] y, int[] z)
static int[]	fromBigInteger(BigInteger x)
static void	inv(int[] x, int[] z)
static boolean	isZero(int[] x)
static void	multiply(int[] x, int[] y, int[] z)
static void	negate(int[] x, int[] z)
static void	square(int[] x, int[] z)
static void	squareN(int[] x, int n, int[] z)
static void	subtract(int[] x, int[] y, int[] z)
static BigInteger	toBigInteger(int[] xMont)
static void	twice(int[] x, int[] z)

Methods inherited from class Object

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

Method Details

add

public static void add(int[] x,
 int[] y,
 int[] z)

subtract

public static void subtract(int[] x,
 int[] y,
 int[] z)

negate

public static void negate(int[] x,
 int[] z)

twice

public static void twice(int[] x,
 int[] z)

multiply

public static void multiply(int[] x,
 int[] y,
 int[] z)

square

public static void square(int[] x,
 int[] z)

squareN

public static void squareN(int[] x,
 int n,
 int[] z)

fromBigInteger

public static int[] fromBigInteger(BigInteger x)

toBigInteger

public static BigInteger toBigInteger(int[] xMont)

inv

public static void inv(int[] x,
 int[] z)

isZero

public static boolean isZero(int[] x)