org.spongycastle.pqc.math.ntru.util

Class ArrayEncoder

java.lang.Object

org.spongycastle.pqc.math.ntru.util.ArrayEncoder

public class ArrayEncoder
extends java.lang.Object

Converts a coefficient array to a compact byte array and vice versa.

Constructor Summary

Constructors

Constructor and Description
ArrayEncoder()

Method Summary

Modifier and Type	Method and Description
static int[]	decodeMod3Sves(byte[] data, int N) Decodes a byte array encoded with encodeMod3Sves(int[]) back to an int array with N coefficients between -1 and 1. Ignores any excess bytes. See P1363.1 section 9.2.2.
static int[]	decodeMod3Tight(byte[] b, int N) Converts a byte array produced by encodeMod3Tight(int[]) back to an int array.
static int[]	decodeMod3Tight(java.io.InputStream is, int N) Converts data produced by encodeMod3Tight(int[]) back to an int array.
static int[]	decodeModQ(byte[] data, int N, int q) Decodes a byte array encoded with encodeModQ(int[], int) back to an int array. N is the number of coefficients.
static int[]	decodeModQ(java.io.InputStream is, int N, int q) Decodes data encoded with encodeModQ(int[], int) back to an int array. N is the number of coefficients.
static byte[]	encodeMod3Sves(int[] arr) Encodes an int array whose elements are between -1 and 1, to a byte array.
static byte[]	encodeMod3Tight(int[] intArray) Encodes an int array whose elements are between -1 and 1, to a byte array.
static byte[]	encodeModQ(int[] a, int q) Encodes an int array whose elements are between 0 and q, to a byte array leaving no gaps between bits. q must be a power of 2.

Methods inherited from class java.lang.Object

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

Constructor Detail

ArrayEncoder

public ArrayEncoder()

Method Detail

encodeModQ

public static byte[] encodeModQ(int[] a,
                                int q)

Encodes an int array whose elements are between 0 and q, to a byte array leaving no gaps between bits.
q must be a power of 2.

Parameters:

a - the input array

q - the modulus

Returns:

the encoded array

decodeModQ

public static int[] decodeModQ(byte[] data,
                               int N,
                               int q)

Decodes a byte array encoded with encodeModQ(int[], int) back to an int array.
N is the number of coefficients. q must be a power of 2.
Ignores any excess bytes.

Parameters:

data - an encoded ternary polynomial

N - number of coefficients

q -

Returns:

an array containing N coefficients between 0 and q-1

decodeModQ

public static int[] decodeModQ(java.io.InputStream is,
                               int N,
                               int q)
                        throws java.io.IOException

Decodes data encoded with encodeModQ(int[], int) back to an int array.
N is the number of coefficients. q must be a power of 2.
Ignores any excess bytes.

Parameters:

is - an encoded ternary polynomial

N - number of coefficients

q -

Returns:

the decoded polynomial

Throws:

java.io.IOException

decodeMod3Sves

public static int[] decodeMod3Sves(byte[] data,
                                   int N)

Decodes a byte array encoded with encodeMod3Sves(int[]) back to an int array with N coefficients between -1 and 1.
Ignores any excess bytes.
See P1363.1 section 9.2.2.

Parameters:

data - an encoded ternary polynomial

N - number of coefficients

Returns:

the decoded coefficients

encodeMod3Sves

public static byte[] encodeMod3Sves(int[] arr)

Encodes an int array whose elements are between -1 and 1, to a byte array. coeffs[2*i] and coeffs[2*i+1] must not both equal -1 for any integer i, so this method is only safe to use with arrays produced by decodeMod3Sves(byte[], int).
See P1363.1 section 9.2.3.

Parameters:

arr -

Returns:

the encoded array

encodeMod3Tight

public static byte[] encodeMod3Tight(int[] intArray)

Encodes an int array whose elements are between -1 and 1, to a byte array.

Returns:

the encoded array

decodeMod3Tight

public static int[] decodeMod3Tight(byte[] b,
                                    int N)

Converts a byte array produced by encodeMod3Tight(int[]) back to an int array.

Parameters:

b - a byte array

N - number of coefficients

Returns:

the decoded array

decodeMod3Tight

public static int[] decodeMod3Tight(java.io.InputStream is,
                                    int N)
                             throws java.io.IOException

Converts data produced by encodeMod3Tight(int[]) back to an int array.

Parameters:

is - an input stream containing the data to decode

N - number of coefficients

Returns:

the decoded array

Throws:

java.io.IOException