diff options
Diffstat (limited to 'core/src/main/java/org/bouncycastle/pqc/crypto/mceliece/Conversions.java')
| -rw-r--r-- | core/src/main/java/org/bouncycastle/pqc/crypto/mceliece/Conversions.java | 236 |
1 files changed, 0 insertions, 236 deletions
diff --git a/core/src/main/java/org/bouncycastle/pqc/crypto/mceliece/Conversions.java b/core/src/main/java/org/bouncycastle/pqc/crypto/mceliece/Conversions.java deleted file mode 100644 index 752d51cc..00000000 --- a/core/src/main/java/org/bouncycastle/pqc/crypto/mceliece/Conversions.java +++ /dev/null @@ -1,236 +0,0 @@ -package org.bouncycastle.pqc.crypto.mceliece; - -import java.math.BigInteger; - -import org.bouncycastle.pqc.math.linearalgebra.BigIntUtils; -import org.bouncycastle.pqc.math.linearalgebra.GF2Vector; -import org.bouncycastle.pqc.math.linearalgebra.IntegerFunctions; - - -/** - * Provides methods for CCA2-Secure Conversions of McEliece PKCS - */ -final class Conversions -{ - private static final BigInteger ZERO = BigInteger.valueOf(0); - private static final BigInteger ONE = BigInteger.valueOf(1); - - /** - * Default constructor (private). - */ - private Conversions() - { - } - - /** - * Encode a number between 0 and (n|t) (binomial coefficient) into a binary - * vector of length n with weight t. The number is given as a byte array. - * Only the first s bits are used, where s = floor[log(n|t)]. - * - * @param n integer - * @param t integer - * @param m the message as a byte array - * @return the encoded message as {@link GF2Vector} - */ - public static GF2Vector encode(final int n, final int t, final byte[] m) - { - if (n < t) - { - throw new IllegalArgumentException("n < t"); - } - - // compute the binomial c = (n|t) - BigInteger c = IntegerFunctions.binomial(n, t); - // get the number encoded in m - BigInteger i = new BigInteger(1, m); - // compare - if (i.compareTo(c) >= 0) - { - throw new IllegalArgumentException("Encoded number too large."); - } - - GF2Vector result = new GF2Vector(n); - - int nn = n; - int tt = t; - for (int j = 0; j < n; j++) - { - c = c.multiply(BigInteger.valueOf(nn - tt)).divide( - BigInteger.valueOf(nn)); - nn--; - if (c.compareTo(i) <= 0) - { - result.setBit(j); - i = i.subtract(c); - tt--; - if (nn == tt) - { - c = ONE; - } - else - { - c = (c.multiply(BigInteger.valueOf(tt + 1))) - .divide(BigInteger.valueOf(nn - tt)); - } - } - } - - return result; - } - - /** - * Decode a binary vector of length n and weight t into a number between 0 - * and (n|t) (binomial coefficient). The result is given as a byte array of - * length floor[(s+7)/8], where s = floor[log(n|t)]. - * - * @param n integer - * @param t integer - * @param vec the binary vector - * @return the decoded vector as a byte array - */ - public static byte[] decode(int n, int t, GF2Vector vec) - { - if ((vec.getLength() != n) || (vec.getHammingWeight() != t)) - { - throw new IllegalArgumentException( - "vector has wrong length or hamming weight"); - } - int[] vecArray = vec.getVecArray(); - - BigInteger bc = IntegerFunctions.binomial(n, t); - BigInteger d = ZERO; - int nn = n; - int tt = t; - for (int i = 0; i < n; i++) - { - bc = bc.multiply(BigInteger.valueOf(nn - tt)).divide( - BigInteger.valueOf(nn)); - nn--; - - int q = i >> 5; - int e = vecArray[q] & (1 << (i & 0x1f)); - if (e != 0) - { - d = d.add(bc); - tt--; - if (nn == tt) - { - bc = ONE; - } - else - { - bc = bc.multiply(BigInteger.valueOf(tt + 1)).divide( - BigInteger.valueOf(nn - tt)); - } - - } - } - - return BigIntUtils.toMinimalByteArray(d); - } - - /** - * Compute a message representative of a message given as a vector of length - * <tt>n</tt> bit and of hamming weight <tt>t</tt>. The result is a - * byte array of length <tt>(s+7)/8</tt>, where - * <tt>s = floor[log(n|t)]</tt>. - * - * @param n integer - * @param t integer - * @param m the message vector as a byte array - * @return a message representative for <tt>m</tt> - */ - public static byte[] signConversion(int n, int t, byte[] m) - { - if (n < t) - { - throw new IllegalArgumentException("n < t"); - } - - BigInteger bc = IntegerFunctions.binomial(n, t); - // finds s = floor[log(binomial(n,t))] - int s = bc.bitLength() - 1; - // s = sq*8 + sr; - int sq = s >> 3; - int sr = s & 7; - if (sr == 0) - { - sq--; - sr = 8; - } - - // n = nq*8+nr; - int nq = n >> 3; - int nr = n & 7; - if (nr == 0) - { - nq--; - nr = 8; - } - // take s bit from m - byte[] data = new byte[nq + 1]; - if (m.length < data.length) - { - System.arraycopy(m, 0, data, 0, m.length); - for (int i = m.length; i < data.length; i++) - { - data[i] = 0; - } - } - else - { - System.arraycopy(m, 0, data, 0, nq); - int h = (1 << nr) - 1; - data[nq] = (byte)(h & m[nq]); - } - - BigInteger d = ZERO; - int nn = n; - int tt = t; - for (int i = 0; i < n; i++) - { - bc = (bc.multiply(new BigInteger(Integer.toString(nn - tt)))) - .divide(new BigInteger(Integer.toString(nn))); - nn--; - - int q = i >>> 3; - int r = i & 7; - r = 1 << r; - byte e = (byte)(r & data[q]); - if (e != 0) - { - d = d.add(bc); - tt--; - if (nn == tt) - { - bc = ONE; - } - else - { - bc = (bc - .multiply(new BigInteger(Integer.toString(tt + 1)))) - .divide(new BigInteger(Integer.toString(nn - tt))); - } - } - } - - byte[] result = new byte[sq + 1]; - byte[] help = d.toByteArray(); - if (help.length < result.length) - { - System.arraycopy(help, 0, result, 0, help.length); - for (int i = help.length; i < result.length; i++) - { - result[i] = 0; - } - } - else - { - System.arraycopy(help, 0, result, 0, sq); - result[sq] = (byte)(((1 << sr) - 1) & help[sq]); - } - - return result; - } - -} |