Package org.bouncycastle.util

Class BigIntegers

  • public final class BigIntegers
extends java.lang.Object
    BigInteger utilities.

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description
      static class  BigIntegers.Cache  

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static java.math.BigInteger ONE  
      static java.math.BigInteger TWO  
      static java.math.BigInteger ZERO  

    • Constructor Summary

      Constructors 
      Constructor Description
      BigIntegers()  

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static boolean areSecretValuesEqual​(int maxLen, java.math.BigInteger a, java.math.BigInteger b)
      Compare two non-negative values for equality without an early exit.
      static byte[] asUnsignedByteArray​(int length, java.math.BigInteger value)
      Return the passed in value as an unsigned byte array of the specified length, padded with leading zeros as necessary..
      static byte[] asUnsignedByteArray​(java.math.BigInteger value)
      Return the passed in value as an unsigned byte array.
      static void asUnsignedByteArray​(java.math.BigInteger value, byte[] buf, int off, int len)
      Write the passed in value as unsigned bytes to the specified buffer range, padded with leading zeros as necessary.
      static byte byteValueExact​(java.math.BigInteger x)  
      static java.math.BigInteger createRandomBigInteger​(int bitLength, java.security.SecureRandom random)
      Return a positive BigInteger in the range of 0 to 2**bitLength - 1.
      static java.math.BigInteger createRandomInRange​(java.math.BigInteger min, java.math.BigInteger max, java.security.SecureRandom random)
      Return a random BigInteger not less than 'min' and not greater than 'max'
      static java.math.BigInteger createRandomPrime​(int bitLength, int certainty, java.security.SecureRandom random)
      Return a prime number candidate of the specified bit length.
      static java.math.BigInteger fromUnsignedByteArray​(byte[] buf)  
      static java.math.BigInteger fromUnsignedByteArray​(byte[] buf, int off, int length)  
      static int getUnsignedByteLength​(java.math.BigInteger n)  
      static boolean hasAnySmallFactors​(java.math.BigInteger x)  
      static int intValueExact​(java.math.BigInteger x)  
      static long longValueExact​(java.math.BigInteger x)  
      static java.math.BigInteger modOddInverse​(java.math.BigInteger M, java.math.BigInteger X)  
      static java.math.BigInteger modOddInverseVar​(java.math.BigInteger M, java.math.BigInteger X)  
      static boolean modOddIsCoprime​(java.math.BigInteger M, java.math.BigInteger X)  
      static boolean modOddIsCoprimeVar​(java.math.BigInteger M, java.math.BigInteger X)  
      static short shortValueExact​(java.math.BigInteger x)  
      static void writeUnsignedByteArray​(java.io.OutputStream out, java.math.BigInteger n)  

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • ZERO

        public static final java.math.BigInteger ZERO

      • ONE

        public static final java.math.BigInteger ONE

      • TWO

        public static final java.math.BigInteger TWO

    • Constructor Detail

      • BigIntegers

        public BigIntegers()

    • Method Detail

      • asUnsignedByteArray

        public static byte[] asUnsignedByteArray​(java.math.BigInteger value)
        Return the passed in value as an unsigned byte array.
        Parameters:
        value - the value to be converted.
        Returns:
        a byte array without a leading zero byte if present in the signed encoding.

      • asUnsignedByteArray

        public static byte[] asUnsignedByteArray​(int length,
                                         java.math.BigInteger value)
        Return the passed in value as an unsigned byte array of the specified length, padded with leading zeros as necessary..
        Parameters:
        length - the fixed length of the result
        value - the value to be converted.
        Returns:
        a byte array padded to a fixed length with leading zeros.

      • asUnsignedByteArray

        public static void asUnsignedByteArray​(java.math.BigInteger value,
                                       byte[] buf,
                                       int off,
                                       int len)
        Write the passed in value as unsigned bytes to the specified buffer range, padded with leading zeros as necessary.
        Parameters:
        value - the value to be converted.
        buf - the buffer to which the value is written.
        off - the start offset in array buf at which the data is written.
        len - the fixed length of data written (possibly padded with leading zeros).

      • createRandomInRange

        public static java.math.BigInteger createRandomInRange​(java.math.BigInteger min,
                                                       java.math.BigInteger max,
                                                       java.security.SecureRandom random)
        Return a random BigInteger not less than 'min' and not greater than 'max'
        Parameters:
        min - the least value that may be generated
        max - the greatest value that may be generated
        random - the source of randomness
        Returns:
        a random BigInteger value in the range [min,max]

      • fromUnsignedByteArray

        public static java.math.BigInteger fromUnsignedByteArray​(byte[] buf)

      • fromUnsignedByteArray

        public static java.math.BigInteger fromUnsignedByteArray​(byte[] buf,
                                                         int off,
                                                         int length)

      • byteValueExact

        public static byte byteValueExact​(java.math.BigInteger x)

      • shortValueExact

        public static short shortValueExact​(java.math.BigInteger x)

      • intValueExact

        public static int intValueExact​(java.math.BigInteger x)

      • longValueExact

        public static long longValueExact​(java.math.BigInteger x)

      • areSecretValuesEqual

        public static boolean areSecretValuesEqual​(int maxLen,
                                           java.math.BigInteger a,
                                           java.math.BigInteger b)
        Compare two non-negative values for equality without an early exit. Both are laid out as unsigned big-endian byte arrays of the fixed public length maxLen before the comparison, so the comparison itself is length-uniform.

        Fixed-width encoding drops the two's-complement sign byte that BigInteger.toByteArray() prepends when the most-significant bit is set: without that, two values could serialise to different lengths (e.g. 256 vs 257 bytes for a 2048-bit value) purely according to that high bit, and the variable-time comparison would leak it. This is not perfectly constant-time — java.math.BigInteger has no constant-time serialisation, so the underlying toByteArray() still runs in time proportional to each value's magnitude — but the comparison no longer differs in length on the value's high bit. Intended for secret key material (RSA d and the CRT factors, DSA/DH/ElGamal/GOST x, EC d), which are all non-negative; the temporary unsigned encodings holding that secret material are zeroed before returning.

        Both arguments must be non-null and non-negative; a negative value does not produce a meaningful result (and may throw IllegalArgumentException), and a null value throws NullPointerException.

        Parameters:
        maxLen - the public unsigned byte length both values are encoded to (e.g. from a group order or modulus).
        a - the first value, non-null and non-negative.
        b - the second value, non-null and non-negative.
        Returns:
        true if a and b are numerically equal, false otherwise.

      • hasAnySmallFactors

        public static boolean hasAnySmallFactors​(java.math.BigInteger x)

      • modOddInverse

        public static java.math.BigInteger modOddInverse​(java.math.BigInteger M,
                                                 java.math.BigInteger X)

      • modOddInverseVar

        public static java.math.BigInteger modOddInverseVar​(java.math.BigInteger M,
                                                    java.math.BigInteger X)

      • modOddIsCoprime

        public static boolean modOddIsCoprime​(java.math.BigInteger M,
                                      java.math.BigInteger X)

      • modOddIsCoprimeVar

        public static boolean modOddIsCoprimeVar​(java.math.BigInteger M,
                                         java.math.BigInteger X)

      • getUnsignedByteLength

        public static int getUnsignedByteLength​(java.math.BigInteger n)

      • createRandomBigInteger

        public static java.math.BigInteger createRandomBigInteger​(int bitLength,
                                                          java.security.SecureRandom random)
        Return a positive BigInteger in the range of 0 to 2**bitLength - 1.
        Parameters:
        bitLength - maximum bit length for the generated BigInteger.
        random - a source of randomness.
        Returns:
        a positive BigInteger

      • createRandomPrime

        public static java.math.BigInteger createRandomPrime​(int bitLength,
                                                     int certainty,
                                                     java.security.SecureRandom random)
        Return a prime number candidate of the specified bit length.
        Parameters:
        bitLength - bit length for the generated BigInteger.
        random - a source of randomness.
        Returns:
        a positive BigInteger of numBits length

      • writeUnsignedByteArray

        public static void writeUnsignedByteArray​(java.io.OutputStream out,
                                          java.math.BigInteger n)
                                   throws java.io.IOException
        Throws:
        java.io.IOException