Util (ECCelerate 6.2 API)

java.lang.Object
- iaik.security.ec.common.Util

```
public final class Util
extends Object
```
Helper class that provides some commonly used methods.
Note that the functions defined in this class are mainly designed to avoid code duplication throughout this library. So while many functions here are defined as public, they may change without further notice. Use these functions at your own risk.
References:
[1] ANSI X9.62-2005, "American National Standard for Financial Services - The Elliptic Curve Digital Signature Algorithm (ECDSA)" , ASC X9, November 2005.
[2] NIST SP800-57 - Part 1, "Recommendation for Key Management", March 2007
[3] NIST SP800-90, "Recommendation for Random Number Generators", March 2007
[4] IEEE P1363.2-2008, "IEEE Standard Specifications for Public-Key Cryptography", 2009

Author:

Christian Hanser, Sebastian Ramacher

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static BigInteger`	`bytesInLEToInt(byte[] array)` Reads a byte array as unsigned 32bit LE BigInteger.
`static BigInteger`	`bytesInLEToInt(byte[] array, int offset)` Reads a byte array as unsigned 32bit LE BigInteger.
`static BigInteger`	`bytesInLEToInt(byte[] array, int offset, int length)` Reads a byte array as unsigned 32bit LE BigInteger.
`static void`	`checkSecureRandom(SecureRandom random, SecurityStrength securityStrength)` Checks whether the given PRNG is a valid NIST SP800-90 PRNG (see [3]) with the required security strength.
`static void`	`checkSecureRandom(String randomAlgorithm, SecurityStrength securityStrength)` Checks whether the given PRNG is a valid NIST SP800-90 PRNG (see [3]) with the required security strength.
`static byte[]`	`intToLEBytes(BigInteger e, int length)` Convert the given BigInteger to a byte array of the given size.
`static byte[]`	`intToOctetString(BigInteger elem, int size)` Integer to Octet String Conversion Primitive or I2OSP as defined in IEEE P1363 (see [4]).
`static byte[]`	`intToOctetString(byte[] elem, int size)` Integer to Octet String Conversion Primitive or I2OSP as defined in IEEE P1363 (see [4]).
`static byte[]`	`revertBytes(byte[] array)` Reverses the order of the elements of the given array.
`static byte[]`	`revertBytes(byte[] array, int length)` Reverts the order of the elements of the given y-coordinate array.
`static String[]`	`splitName(String name)` Split names separated by \|.
`static BigDecimal`	`sqrt(BigInteger n)` This method computes the square root of a `BigInteger`.
`static String`	`toString(byte[] arr)` Returns a representation of an byte array as a hex string.
`static String`	`toString(ECPoint p)` Returns a `String` representation of a `ECPoint` instance.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Method Detail
  - revertBytes
```
public static byte[] revertBytes(byte[] array)
```
    Reverses the order of the elements of the given array. In fact this means LE to BE conversion.
    
    Parameters:
    
    array - array to be reversed
    
    Returns:
    
    byte array containing the elements of array in reversed order
  - revertBytes
```
public static byte[] revertBytes(byte[] array,
                                 int length)
```
    Reverts the order of the elements of the given y-coordinate array. In fact this means LE to BE conversion.
    
    Parameters:
    
    array - the encoded point without the x-coordinate bit
    
    length - the length to be considered
    
    Returns:
    
    byte array for the field_.newElement method
  - intToLEBytes
```
public static byte[] intToLEBytes(BigInteger e,
                                  int length)
```
    Convert the given BigInteger to a byte array of the given size. This a helper method for the 32byte encoding specified in [0].
    
    Parameters:
    
    e - the BigInteger to encode
    
    length - the length of the resulting byte array (trailing bits get lost)
    
    Returns:
    
    a byte[] in little endian holding
  - bytesInLEToInt
```
public static BigInteger bytesInLEToInt(byte[] array)
```
    Reads a byte array as unsigned 32bit LE BigInteger. Unlike BigInteger(byte[]) the byte array is unread as unsigned integer.
    
    Parameters:
    
    array - the array
    
    Returns:
    
    BigInteger corresponding to given byte array
  - bytesInLEToInt
```
public static BigInteger bytesInLEToInt(byte[] array,
                                        int offset)
```
    Reads a byte array as unsigned 32bit LE BigInteger. Unlike BigInteger(byte[]) the byte array is unread as unsigned integer.
    
    Parameters:
    
    array - the array
    
    offset - the offset
    
    Returns:
    
    BigInteger corresponding to given byte array
  - bytesInLEToInt
```
public static BigInteger bytesInLEToInt(byte[] array,
                                        int offset,
                                        int length)
```
    Reads a byte array as unsigned 32bit LE BigInteger. Unlike BigInteger(byte[]) the byte array is unread as unsigned integer.
    
    Parameters:
    
    array - the array
    
    offset - the offset
    
    length - the length
    
    Returns:
    
    BigInteger corresponding to given byte array
  - intToOctetString
```
public static byte[] intToOctetString(BigInteger elem,
                                      int size)
```
    Integer to Octet String Conversion Primitive or I2OSP as defined in IEEE P1363 (see [4]).
    
    Parameters:
    
    elem - the integer to be converted
    
    size - the length of the result array. if this parameter is shorter than the required size it will be ignored.
    
    Returns:
    
    the octet string as a byte[] in big-endian byte order: the most significant byte is in the zeroth element
  - intToOctetString
```
public static byte[] intToOctetString(byte[] elem,
                                      int size)
```
    Integer to Octet String Conversion Primitive or I2OSP as defined in IEEE P1363 (see [4]).
    
    Parameters:
    
    elem - the integer to be converted
    
    size - the length of the result array. If this parameter is shorter than the required size it will be ignored.
    
    Returns:
    
    the octet string as a byte[] in big-endian byte order: the most significant byte is in the zeroth element
  - checkSecureRandom
```
public static void checkSecureRandom(SecureRandom random,
                                     SecurityStrength securityStrength)
                              throws IllegalArgumentException
```
    Checks whether the given PRNG is a valid NIST SP800-90 PRNG (see [3]) with the required security strength.
    
    Parameters:
    
    random - the PRNG instance
    
    securityStrength - the desired security strength
    
    Throws:
    
    IllegalArgumentException - if the PRNG is not a NIST PRNG or if it does not have the required security strength
  - checkSecureRandom
```
public static void checkSecureRandom(String randomAlgorithm,
                                     SecurityStrength securityStrength)
                              throws IllegalArgumentException
```
    Checks whether the given PRNG is a valid NIST SP800-90 PRNG (see [3]) with the required security strength.
    
    Parameters:
    
    randomAlgorithm - the PRNG algorithm name
    
    securityStrength - the desired security strength
    
    Throws:
    
    IllegalArgumentException - if the PRNG is not a NIST PRNG or if it does not have the required security strength
  - toString
```
public static String toString(ECPoint p)
```
    Returns a String representation of a ECPoint instance.
    
    Parameters:
    
    p - the ECPoint
    
    Returns:
    
    a String describing the given point
  - toString
```
public static String toString(byte[] arr)
```
    Returns a representation of an byte array as a hex string.
    
    Parameters:
    
    arr - byte array
    
    Returns:
    
    a hex string representation of arr
  - sqrt
```
public static BigDecimal sqrt(BigInteger n)
```
    This method computes the square root of a BigInteger.
    
    Parameters:
    
    n - the integer
    
    Returns:
    
    the square root of n
  - splitName
```
public static String[] splitName(String name)
```
    Split names separated by |.
    
    Parameters:
    
    name - a sequence of names separated by |
    
    Returns:
    
    array of names

Class Util

Method Summary

Methods inherited from class java.lang.Object

Method Detail

revertBytes

revertBytes

intToLEBytes

bytesInLEToInt

bytesInLEToInt

bytesInLEToInt

intToOctetString

intToOctetString

checkSecureRandom

checkSecureRandom

toString

toString

sqrt

splitName