org.spongycastle.math.ec

Class WNafUtil

java.lang.Object

org.spongycastle.math.ec.WNafUtil

public abstract class WNafUtil
extends java.lang.Object

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	PRECOMP_NAME

Constructor Summary

Constructors

Constructor and Description
WNafUtil()

Method Summary

Modifier and Type	Method and Description
static int[]	generateCompactNaf(java.math.BigInteger k)
static int[]	generateCompactWindowNaf(int width, java.math.BigInteger k)
static byte[]	generateJSF(java.math.BigInteger g, java.math.BigInteger h)
static byte[]	generateNaf(java.math.BigInteger k)
static byte[]	generateWindowNaf(int width, java.math.BigInteger k) Computes the Window NAF (non-adjacent Form) of an integer.
static int	getNafWeight(java.math.BigInteger k)
static int	getWindowSize(int bits) Determine window width to use for a scalar multiplication of the given size.
static int	getWindowSize(int bits, int[] windowSizeCutoffs) Determine window width to use for a scalar multiplication of the given size.
static WNafPreCompInfo	getWNafPreCompInfo(ECPoint p)
static WNafPreCompInfo	getWNafPreCompInfo(PreCompInfo preCompInfo)
static ECPoint	mapPointWithPrecomp(ECPoint p, int width, boolean includeNegated, ECPointMap pointMap)
static WNafPreCompInfo	precompute(ECPoint p, int width, boolean includeNegated)

Methods inherited from class java.lang.Object

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

Field Detail

PRECOMP_NAME

public static final java.lang.String PRECOMP_NAME

See Also:

Constant Field Values

Constructor Detail

WNafUtil

public WNafUtil()

Method Detail

generateCompactNaf

public static int[] generateCompactNaf(java.math.BigInteger k)

generateCompactWindowNaf

public static int[] generateCompactWindowNaf(int width,
                                             java.math.BigInteger k)

generateJSF

public static byte[] generateJSF(java.math.BigInteger g,
                                 java.math.BigInteger h)

generateNaf

public static byte[] generateNaf(java.math.BigInteger k)

generateWindowNaf

public static byte[] generateWindowNaf(int width,
                                       java.math.BigInteger k)

Computes the Window NAF (non-adjacent Form) of an integer.

Parameters:

width - The width w of the Window NAF. The width is defined as the minimal number w, such that for any w consecutive digits in the resulting representation, at most one is non-zero.

k - The integer of which the Window NAF is computed.

Returns:

The Window NAF of the given width, such that the following holds: k = ∑i=0l-1 ki2i , where the ki denote the elements of the returned byte[].

getNafWeight

public static int getNafWeight(java.math.BigInteger k)

getWNafPreCompInfo

public static WNafPreCompInfo getWNafPreCompInfo(ECPoint p)

getWNafPreCompInfo

public static WNafPreCompInfo getWNafPreCompInfo(PreCompInfo preCompInfo)

getWindowSize

public static int getWindowSize(int bits)

Determine window width to use for a scalar multiplication of the given size.

Parameters:

bits - the bit-length of the scalar to multiply by

Returns:

the window size to use

getWindowSize

public static int getWindowSize(int bits,
                                int[] windowSizeCutoffs)

Determine window width to use for a scalar multiplication of the given size.

Parameters:

bits - the bit-length of the scalar to multiply by

windowSizeCutoffs - a monotonically increasing list of bit sizes at which to increment the window width

Returns:

the window size to use

mapPointWithPrecomp

public static ECPoint mapPointWithPrecomp(ECPoint p,
                                          int width,
                                          boolean includeNegated,
                                          ECPointMap pointMap)

precompute

public static WNafPreCompInfo precompute(ECPoint p,
                                         int width,
                                         boolean includeNegated)