org.bouncycastle.util.BigIntegers Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of bcprov-ext-debug-jdk18on Show documentation
Show all versions of bcprov-ext-debug-jdk18on Show documentation
The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for Java 1.8 and later with debug enabled.
The newest version!
package org.bouncycastle.util;
import java.math.BigInteger;
import java.security.SecureRandom;
import java.util.Map;
import java.util.WeakHashMap;
import org.bouncycastle.math.raw.Mod;
import org.bouncycastle.math.raw.Nat;
/**
* BigInteger utilities.
*/
public final class BigIntegers
{
public static final BigInteger ZERO = BigInteger.valueOf(0);
public static final BigInteger ONE = BigInteger.valueOf(1);
public static final BigInteger TWO = BigInteger.valueOf(2);
private static final BigInteger THREE = BigInteger.valueOf(3);
private static final int MAX_ITERATIONS = 1000;
/**
* Return the passed in value as an unsigned byte array.
*
* @param value the value to be converted.
* @return a byte array without a leading zero byte if present in the signed encoding.
*/
public static byte[] asUnsignedByteArray(
BigInteger value)
{
byte[] bytes = value.toByteArray();
if (bytes[0] == 0 && bytes.length != 1)
{
byte[] tmp = new byte[bytes.length - 1];
System.arraycopy(bytes, 1, tmp, 0, tmp.length);
return tmp;
}
return bytes;
}
/**
* Return the passed in value as an unsigned byte array of the specified length, padded with
* leading zeros as necessary..
*
* @param length the fixed length of the result
* @param value the value to be converted.
* @return a byte array padded to a fixed length with leading zeros.
*/
public static byte[] asUnsignedByteArray(int length, BigInteger value)
{
byte[] bytes = value.toByteArray();
if (bytes.length == length)
{
return bytes;
}
int start = (bytes[0] == 0 && bytes.length != 1) ? 1 : 0;
int count = bytes.length - start;
if (count > length)
{
throw new IllegalArgumentException("standard length exceeded for value");
}
byte[] tmp = new byte[length];
System.arraycopy(bytes, start, tmp, tmp.length - count, count);
return tmp;
}
/**
* Write the passed in value as unsigned bytes to the specified buffer range, padded with
* leading zeros as necessary.
*
* @param value the value to be converted.
* @param buf the buffer to which the value is written.
* @param off the start offset in array buf at which the data is written.
* @param len the fixed length of data written (possibly padded with leading zeros).
*/
public static void asUnsignedByteArray(BigInteger value, byte[] buf, int off, int len)
{
byte[] bytes = value.toByteArray();
if (bytes.length == len)
{
System.arraycopy(bytes, 0, buf, off, len);
return;
}
int start = (bytes[0] == 0 && bytes.length != 1) ? 1 : 0;
int count = bytes.length - start;
if (count > len)
{
throw new IllegalArgumentException("standard length exceeded for value");
}
int padLen = len - count;
Arrays.fill(buf, off, off + padLen, (byte)0x00);
System.arraycopy(bytes, start, buf, off + padLen, count);
}
/**
* Return a random BigInteger not less than 'min' and not greater than 'max'
*
* @param min the least value that may be generated
* @param max the greatest value that may be generated
* @param random the source of randomness
* @return a random BigInteger value in the range [min,max]
*/
public static BigInteger createRandomInRange(
BigInteger min,
BigInteger max,
SecureRandom random)
{
int cmp = min.compareTo(max);
if (cmp >= 0)
{
if (cmp > 0)
{
throw new IllegalArgumentException("'min' may not be greater than 'max'");
}
return min;
}
if (min.bitLength() > max.bitLength() / 2)
{
return createRandomInRange(ZERO, max.subtract(min), random).add(min);
}
for (int i = 0; i < MAX_ITERATIONS; ++i)
{
BigInteger x = createRandomBigInteger(max.bitLength(), random);
if (x.compareTo(min) >= 0 && x.compareTo(max) <= 0)
{
return x;
}
}
// fall back to a faster (restricted) method
return createRandomBigInteger(max.subtract(min).bitLength() - 1, random).add(min);
}
public static BigInteger fromUnsignedByteArray(byte[] buf)
{
return new BigInteger(1, buf);
}
public static BigInteger fromUnsignedByteArray(byte[] buf, int off, int length)
{
byte[] mag = buf;
if (off != 0 || length != buf.length)
{
mag = new byte[length];
System.arraycopy(buf, off, mag, 0, length);
}
return new BigInteger(1, mag);
}
public static byte byteValueExact(BigInteger x)
{
// Since Java 1.8 could use BigInteger.byteValueExact instead
if (x.bitLength() > 7)
{
throw new ArithmeticException("BigInteger out of int range");
}
return x.byteValue();
}
public static short shortValueExact(BigInteger x)
{
// Since Java 1.8 could use BigInteger.shortValueExact instead
if (x.bitLength() > 15)
{
throw new ArithmeticException("BigInteger out of int range");
}
return x.shortValue();
}
public static int intValueExact(BigInteger x)
{
// Since Java 1.8 could use BigInteger.intValueExact instead
if (x.bitLength() > 31)
{
throw new ArithmeticException("BigInteger out of int range");
}
return x.intValue();
}
public static long longValueExact(BigInteger x)
{
// Since Java 1.8 could use BigInteger.longValueExact instead
if (x.bitLength() > 63)
{
throw new ArithmeticException("BigInteger out of long range");
}
return x.longValue();
}
public static BigInteger modOddInverse(BigInteger M, BigInteger X)
{
if (!M.testBit(0))
{
throw new IllegalArgumentException("'M' must be odd");
}
if (M.signum() != 1)
{
throw new ArithmeticException("BigInteger: modulus not positive");
}
if (X.signum() < 0 || X.compareTo(M) >= 0)
{
X = X.mod(M);
}
int bits = M.bitLength();
int[] m = Nat.fromBigInteger(bits, M);
int[] x = Nat.fromBigInteger(bits, X);
int len = m.length;
int[] z = Nat.create(len);
if (0 == Mod.modOddInverse(m, x, z))
{
throw new ArithmeticException("BigInteger not invertible.");
}
return Nat.toBigInteger(len, z);
}
public static BigInteger modOddInverseVar(BigInteger M, BigInteger X)
{
if (!M.testBit(0))
{
throw new IllegalArgumentException("'M' must be odd");
}
if (M.signum() != 1)
{
throw new ArithmeticException("BigInteger: modulus not positive");
}
if (M.equals(ONE))
{
return ZERO;
}
if (X.signum() < 0 || X.compareTo(M) >= 0)
{
X = X.mod(M);
}
if (X.equals(ONE))
{
return ONE;
}
int bits = M.bitLength();
int[] m = Nat.fromBigInteger(bits, M);
int[] x = Nat.fromBigInteger(bits, X);
int len = m.length;
int[] z = Nat.create(len);
if (!Mod.modOddInverseVar(m, x, z))
{
throw new ArithmeticException("BigInteger not invertible.");
}
return Nat.toBigInteger(len, z);
}
public static int getUnsignedByteLength(BigInteger n)
{
if (n.equals(ZERO))
{
return 1;
}
return (n.bitLength() + 7) / 8;
}
/**
* Return a positive BigInteger in the range of 0 to 2**bitLength - 1.
*
* @param bitLength maximum bit length for the generated BigInteger.
* @param random a source of randomness.
* @return a positive BigInteger
*/
public static BigInteger createRandomBigInteger(int bitLength, SecureRandom random)
{
return new BigInteger(1, createRandom(bitLength, random));
}
// Hexadecimal value of the product of the 131 smallest odd primes from 3 to 743
private static final BigInteger SMALL_PRIMES_PRODUCT = new BigInteger(
"8138e8a0fcf3a4e84a771d40fd305d7f4aa59306d7251de54d98af8fe95729a1f"
+ "73d893fa424cd2edc8636a6c3285e022b0e3866a565ae8108eed8591cd4fe8d2"
+ "ce86165a978d719ebf647f362d33fca29cd179fb42401cbaf3df0c614056f9c8"
+ "f3cfd51e474afb6bc6974f78db8aba8e9e517fded658591ab7502bd41849462f",
16);
private static final int MAX_SMALL = BigInteger.valueOf(743).bitLength(); // bitlength of 743 * 743
/**
* Return a prime number candidate of the specified bit length.
*
* @param bitLength bit length for the generated BigInteger.
* @param random a source of randomness.
* @return a positive BigInteger of numBits length
*/
public static BigInteger createRandomPrime(int bitLength, int certainty, SecureRandom random)
{
if (bitLength < 2)
{
throw new IllegalArgumentException("bitLength < 2");
}
BigInteger rv;
if (bitLength == 2)
{
return (random.nextInt() < 0) ? TWO : THREE;
}
do
{
byte[] base = createRandom(bitLength, random);
int xBits = 8 * base.length - bitLength;
byte lead = (byte)(1 << (7 - xBits));
// ensure top and bottom bit set
base[0] |= lead;
base[base.length - 1] |= 0x01;
rv = new BigInteger(1, base);
if (bitLength > MAX_SMALL)
{
while (!rv.gcd(SMALL_PRIMES_PRODUCT).equals(ONE))
{
rv = rv.add(TWO);
}
}
}
while (!rv.isProbablePrime(certainty));
return rv;
}
private static byte[] createRandom(int bitLength, SecureRandom random)
throws IllegalArgumentException
{
if (bitLength < 1)
{
throw new IllegalArgumentException("bitLength must be at least 1");
}
int nBytes = (bitLength + 7) / 8;
byte[] rv = new byte[nBytes];
random.nextBytes(rv);
// strip off any excess bits in the MSB
int xBits = 8 * nBytes - bitLength;
rv[0] &= (byte)(255 >>> xBits);
return rv;
}
public static class Cache
{
private final Map values = new WeakHashMap();
private final BigInteger[] preserve = new BigInteger[8];
private int preserveCounter = 0;
public synchronized void add(BigInteger value)
{
values.put(value, Boolean.TRUE);
preserve[preserveCounter] = value;
preserveCounter = (preserveCounter + 1) % preserve.length;
}
public synchronized boolean contains(BigInteger value)
{
return values.containsKey(value);
}
public synchronized int size()
{
return values.size();
}
public synchronized void clear()
{
values.clear();
for (int i = 0; i != preserve.length; i++)
{
preserve[i] = null;
}
}
}
}