1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
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   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
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  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package sun.security.util.math;
  27 
  28 import java.math.BigInteger;
  29 
  30 /**
  31  * An interface for the field of integers modulo a prime number. An
  32  * implementation of this interface can be used to get properties of the
  33  * field and to produce field elements of type ImmutableIntegerModuloP from
  34  * other objects and representations of field elements.
  35  */
  36 
  37 public interface IntegerFieldModuloP {
  38 
  39     /**
  40      * Get the size of the field as a BigInteger. This size is equal to the
  41      * prime modulus used to construct the field.
  42      *
  43      * @return the size of the field.
  44      */
  45     BigInteger getSize();
  46 
  47     /**
  48      * Get the additive identity element 0
  49      *
  50      * @return the additive identity element
  51      */
  52     ImmutableIntegerModuloP get0();
  53 
  54     /**
  55      * Get the multiplicative identity element 1
  56      *
  57      * @return the multiplicative identity element
  58      */
  59     ImmutableIntegerModuloP get1();
  60 
  61     /**
  62      * Get the field element equivalent to the supplied BigInteger value. The
  63      * supplied value may be negative or larger than the modulus that defines
  64      * the field.
  65      *
  66      * @param v a BigInteger value
  67      * @return the field element corresponding to v
  68      */
  69     ImmutableIntegerModuloP getElement(BigInteger v);
  70 
  71     /**
  72      * Get a "small" value according to this implementation. This value may
  73      * be used in optimized forms of some operations to avoid unnecessary
  74      * calculations. For example, multiplication is much faster when it is
  75      * known that one of the numbers fits within a single limb.
  76      *
  77      * The definition of "small", and the range of accepted values, is
  78      * implementation-specific.
  79      *
  80      * @param v the small integer value
  81      * @throws IllegalArgumentException when the value is not small
  82      */
  83     SmallValue getSmallValue(int v);
  84 
  85     /**
  86      * Get a field element from a little-endian unsigned integer stored in an
  87      * array. The entire array will be used, and the supplied value may be
  88      * larger than the modulus that defines the field. The array will not be
  89      * modified.
  90      *
  91      * @param v an array containing a little-endian unsigned integer
  92      * @return the field element corresponding to v
  93      */
  94     default ImmutableIntegerModuloP getElement(byte[] v) {
  95         return getElement(v, 0, v.length, (byte) 0);
  96     }
  97 
  98     /**
  99      * Get a field element from a little-endian unsigned integer stored at the
 100      * specified position in an array. The supplied value may be
 101      * larger than the modulus that defines the field. This method also takes
 102      * a byte which is interpreted as an additional high-order byte of the
 103      * number. The array will not be modified.
 104      *
 105      * @param v an array containing a little-endian unsigned integer
 106      * @param offset the starting position of the integer
 107      * @param length the number of bytes to read
 108      * @param highByte the high-order byte of the number
 109      * @return the field element corresponding to the bytes at the specified
 110      *     position
 111      */
 112     ImmutableIntegerModuloP getElement(byte[] v, int offset, int length,
 113                                        byte highByte);
 114 }
 115