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Diffstat (limited to 'core/src/main/java/org/bouncycastle/pqc/math/ntru/util/ArrayEncoder.java')
-rw-r--r--core/src/main/java/org/bouncycastle/pqc/math/ntru/util/ArrayEncoder.java292
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diff --git a/core/src/main/java/org/bouncycastle/pqc/math/ntru/util/ArrayEncoder.java b/core/src/main/java/org/bouncycastle/pqc/math/ntru/util/ArrayEncoder.java
deleted file mode 100644
index a437d48a..00000000
--- a/core/src/main/java/org/bouncycastle/pqc/math/ntru/util/ArrayEncoder.java
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@@ -1,292 +0,0 @@
-package org.bouncycastle.pqc.math.ntru.util;
-
-import java.io.IOException;
-import java.io.InputStream;
-import java.math.BigInteger;
-
-import org.bouncycastle.util.Arrays;
-
-/**
- * Converts a coefficient array to a compact byte array and vice versa.
- */
-public class ArrayEncoder
-{
- /**
- * Bit string to coefficient conversion table from P1363.1. Also found at
- * {@link http://stackoverflow.com/questions/1562548/how-to-make-a-message-into-a-polynomial}
- * <p/>
- * Convert each three-bit quantity to two ternary coefficients as follows, and concatenate the resulting
- * ternary quantities to obtain [the output].
- * <p/>
- * <code>
- * {0, 0, 0} -> {0, 0}<br/>
- * {0, 0, 1} -> {0, 1}<br/>
- * {0, 1, 0} -> {0, -1}<br/>
- * {0, 1, 1} -> {1, 0}<br/>
- * {1, 0, 0} -> {1, 1}<br/>
- * {1, 0, 1} -> {1, -1}<br/>
- * {1, 1, 0} -> {-1, 0}<br/>
- * {1, 1, 1} -> {-1, 1}<br/>
- * </code>
- */
- private static final int[] COEFF1_TABLE = {0, 0, 0, 1, 1, 1, -1, -1};
- private static final int[] COEFF2_TABLE = {0, 1, -1, 0, 1, -1, 0, 1};
- /**
- * Coefficient to bit string conversion table from P1363.1. Also found at
- * {@link http://stackoverflow.com/questions/1562548/how-to-make-a-message-into-a-polynomial}
- * <p/>
- * Convert each set of two ternary coefficients to three bits as follows, and concatenate the resulting bit
- * quantities to obtain [the output]:
- * <p/>
- * <code>
- * {-1, -1} -> set "fail" to 1 and set bit string to {1, 1, 1}
- * {-1, 0} -> {1, 1, 0}<br/>
- * {-1, 1} -> {1, 1, 1}<br/>
- * {0, -1} -> {0, 1, 0}<br/>
- * {0, 0} -> {0, 0, 0}<br/>
- * {0, 1} -> {0, 0, 1}<br/>
- * {1, -1} -> {1, 0, 1}<br/>
- * {1, 0} -> {0, 1, 1}<br/>
- * {1, 1} -> {1, 0, 0}<br/>
- * </code>
- */
- private static final int[] BIT1_TABLE = {1, 1, 1, 0, 0, 0, 1, 0, 1};
- private static final int[] BIT2_TABLE = {1, 1, 1, 1, 0, 0, 0, 1, 0};
- private static final int[] BIT3_TABLE = {1, 0, 1, 0, 0, 1, 1, 1, 0};
-
- /**
- * Encodes an int array whose elements are between 0 and <code>q</code>,
- * to a byte array leaving no gaps between bits.<br>
- * <code>q</code> must be a power of 2.
- *
- * @param a the input array
- * @param q the modulus
- * @return the encoded array
- */
- public static byte[] encodeModQ(int[] a, int q)
- {
- int bitsPerCoeff = 31 - Integer.numberOfLeadingZeros(q);
- int numBits = a.length * bitsPerCoeff;
- int numBytes = (numBits + 7) / 8;
- byte[] data = new byte[numBytes];
- int bitIndex = 0;
- int byteIndex = 0;
- for (int i = 0; i < a.length; i++)
- {
- for (int j = 0; j < bitsPerCoeff; j++)
- {
- int currentBit = (a[i] >> j) & 1;
- data[byteIndex] |= currentBit << bitIndex;
- if (bitIndex == 7)
- {
- bitIndex = 0;
- byteIndex++;
- }
- else
- {
- bitIndex++;
- }
- }
- }
- return data;
- }
-
- /**
- * Decodes a <code>byte</code> array encoded with {@link #encodeModQ(int[], int)} back to an <code>int</code> array.<br>
- * <code>N</code> is the number of coefficients. <code>q</code> must be a power of <code>2</code>.<br>
- * Ignores any excess bytes.
- *
- * @param data an encoded ternary polynomial
- * @param N number of coefficients
- * @param q
- * @return an array containing <code>N</code> coefficients between <code>0</code> and <code>q-1</code>
- */
- public static int[] decodeModQ(byte[] data, int N, int q)
- {
- int[] coeffs = new int[N];
- int bitsPerCoeff = 31 - Integer.numberOfLeadingZeros(q);
- int numBits = N * bitsPerCoeff;
- int coeffIndex = 0;
- for (int bitIndex = 0; bitIndex < numBits; bitIndex++)
- {
- if (bitIndex > 0 && bitIndex % bitsPerCoeff == 0)
- {
- coeffIndex++;
- }
- int bit = getBit(data, bitIndex);
- coeffs[coeffIndex] += bit << (bitIndex % bitsPerCoeff);
- }
- return coeffs;
- }
-
- /**
- * Decodes data encoded with {@link #encodeModQ(int[], int)} back to an <code>int</code> array.<br>
- * <code>N</code> is the number of coefficients. <code>q</code> must be a power of <code>2</code>.<br>
- * Ignores any excess bytes.
- *
- * @param is an encoded ternary polynomial
- * @param N number of coefficients
- * @param q
- * @return the decoded polynomial
- */
- public static int[] decodeModQ(InputStream is, int N, int q)
- throws IOException
- {
- int qBits = 31 - Integer.numberOfLeadingZeros(q);
- int size = (N * qBits + 7) / 8;
- byte[] arr = Util.readFullLength(is, size);
- return decodeModQ(arr, N, q);
- }
-
- /**
- * Decodes a <code>byte</code> array encoded with {@link #encodeMod3Sves(int[])} back to an <code>int</code> array
- * with <code>N</code> coefficients between <code>-1</code> and <code>1</code>.<br>
- * Ignores any excess bytes.<br>
- * See P1363.1 section 9.2.2.
- *
- * @param data an encoded ternary polynomial
- * @param N number of coefficients
- * @return the decoded coefficients
- */
- public static int[] decodeMod3Sves(byte[] data, int N)
- {
- int[] coeffs = new int[N];
- int coeffIndex = 0;
- for (int bitIndex = 0; bitIndex < data.length * 8; )
- {
- int bit1 = getBit(data, bitIndex++);
- int bit2 = getBit(data, bitIndex++);
- int bit3 = getBit(data, bitIndex++);
- int coeffTableIndex = bit1 * 4 + bit2 * 2 + bit3;
- coeffs[coeffIndex++] = COEFF1_TABLE[coeffTableIndex];
- coeffs[coeffIndex++] = COEFF2_TABLE[coeffTableIndex];
- // ignore bytes that can't fit
- if (coeffIndex > N - 2)
- {
- break;
- }
- }
- return coeffs;
- }
-
- /**
- * Encodes an <code>int</code> array whose elements are between <code>-1</code> and <code>1</code>, to a byte array.
- * <code>coeffs[2*i]</code> and <code>coeffs[2*i+1]</code> must not both equal -1 for any integer <code>i</code>,
- * so this method is only safe to use with arrays produced by {@link #decodeMod3Sves(byte[], int)}.<br>
- * See P1363.1 section 9.2.3.
- *
- * @param arr
- * @return the encoded array
- */
- public static byte[] encodeMod3Sves(int[] arr)
- {
- int numBits = (arr.length * 3 + 1) / 2;
- int numBytes = (numBits + 7) / 8;
- byte[] data = new byte[numBytes];
- int bitIndex = 0;
- int byteIndex = 0;
- for (int i = 0; i < arr.length / 2 * 2; )
- { // if length is an odd number, throw away the highest coeff
- int coeff1 = arr[i++] + 1;
- int coeff2 = arr[i++] + 1;
- if (coeff1 == 0 && coeff2 == 0)
- {
- throw new IllegalStateException("Illegal encoding!");
- }
- int bitTableIndex = coeff1 * 3 + coeff2;
- int[] bits = new int[]{BIT1_TABLE[bitTableIndex], BIT2_TABLE[bitTableIndex], BIT3_TABLE[bitTableIndex]};
- for (int j = 0; j < 3; j++)
- {
- data[byteIndex] |= bits[j] << bitIndex;
- if (bitIndex == 7)
- {
- bitIndex = 0;
- byteIndex++;
- }
- else
- {
- bitIndex++;
- }
- }
- }
- return data;
- }
-
- /**
- * Encodes an <code>int</code> array whose elements are between <code>-1</code> and <code>1</code>, to a byte array.
- *
- * @return the encoded array
- */
- public static byte[] encodeMod3Tight(int[] intArray)
- {
- BigInteger sum = BigInteger.ZERO;
- for (int i = intArray.length - 1; i >= 0; i--)
- {
- sum = sum.multiply(BigInteger.valueOf(3));
- sum = sum.add(BigInteger.valueOf(intArray[i] + 1));
- }
-
- int size = (BigInteger.valueOf(3).pow(intArray.length).bitLength() + 7) / 8;
- byte[] arr = sum.toByteArray();
-
- if (arr.length < size)
- {
- // pad with leading zeros so arr.length==size
- byte[] arr2 = new byte[size];
- System.arraycopy(arr, 0, arr2, size - arr.length, arr.length);
- return arr2;
- }
-
- if (arr.length > size)
- // drop sign bit
- {
- arr = Arrays.copyOfRange(arr, 1, arr.length);
- }
- return arr;
- }
-
- /**
- * Converts a byte array produced by {@link #encodeMod3Tight(int[])} back to an <code>int</code> array.
- *
- * @param b a byte array
- * @param N number of coefficients
- * @return the decoded array
- */
- public static int[] decodeMod3Tight(byte[] b, int N)
- {
- BigInteger sum = new BigInteger(1, b);
- int[] coeffs = new int[N];
- for (int i = 0; i < N; i++)
- {
- coeffs[i] = sum.mod(BigInteger.valueOf(3)).intValue() - 1;
- if (coeffs[i] > 1)
- {
- coeffs[i] -= 3;
- }
- sum = sum.divide(BigInteger.valueOf(3));
- }
- return coeffs;
- }
-
- /**
- * Converts data produced by {@link #encodeMod3Tight(int[])} back to an <code>int</code> array.
- *
- * @param is an input stream containing the data to decode
- * @param N number of coefficients
- * @return the decoded array
- */
- public static int[] decodeMod3Tight(InputStream is, int N)
- throws IOException
- {
- int size = (int)Math.ceil(N * Math.log(3) / Math.log(2) / 8);
- byte[] arr = Util.readFullLength(is, size);
- return decodeMod3Tight(arr, N);
- }
-
- private static int getBit(byte[] arr, int bitIndex)
- {
- int byteIndex = bitIndex / 8;
- int arrElem = arr[byteIndex] & 0xFF;
- return (arrElem >> (bitIndex % 8)) & 1;
- }
-} \ No newline at end of file
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