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      1 package org.bouncycastle.math.ec.custom.sec;
      2 
      3 import java.math.BigInteger;
      4 
      5 import org.bouncycastle.math.ec.ECFieldElement;
      6 import org.bouncycastle.math.raw.Mod;
      7 import org.bouncycastle.math.raw.Nat192;
      8 import org.bouncycastle.util.Arrays;
      9 
     10 public class SecP192K1FieldElement extends ECFieldElement.AbstractFp
     11 {
     12     public static final BigInteger Q = SecP192K1Curve.q;
     13 
     14     protected int[] x;
     15 
     16     public SecP192K1FieldElement(BigInteger x)
     17     {
     18         if (x == null || x.signum() < 0 || x.compareTo(Q) >= 0)
     19         {
     20             throw new IllegalArgumentException("x value invalid for SecP192K1FieldElement");
     21         }
     22 
     23         this.x = SecP192K1Field.fromBigInteger(x);
     24     }
     25 
     26     public SecP192K1FieldElement()
     27     {
     28         this.x = Nat192.create();
     29     }
     30 
     31     protected SecP192K1FieldElement(int[] x)
     32     {
     33         this.x = x;
     34     }
     35 
     36     public boolean isZero()
     37     {
     38         return Nat192.isZero(x);
     39     }
     40 
     41     public boolean isOne()
     42     {
     43         return Nat192.isOne(x);
     44     }
     45 
     46     public boolean testBitZero()
     47     {
     48         return Nat192.getBit(x, 0) == 1;
     49     }
     50 
     51     public BigInteger toBigInteger()
     52     {
     53         return Nat192.toBigInteger(x);
     54     }
     55 
     56     public String getFieldName()
     57     {
     58         return "SecP192K1Field";
     59     }
     60 
     61     public int getFieldSize()
     62     {
     63         return Q.bitLength();
     64     }
     65 
     66     public ECFieldElement add(ECFieldElement b)
     67     {
     68         int[] z = Nat192.create();
     69         SecP192K1Field.add(x, ((SecP192K1FieldElement)b).x, z);
     70         return new SecP192K1FieldElement(z);
     71     }
     72 
     73     public ECFieldElement addOne()
     74     {
     75         int[] z = Nat192.create();
     76         SecP192K1Field.addOne(x, z);
     77         return new SecP192K1FieldElement(z);
     78     }
     79 
     80     public ECFieldElement subtract(ECFieldElement b)
     81     {
     82         int[] z = Nat192.create();
     83         SecP192K1Field.subtract(x, ((SecP192K1FieldElement)b).x, z);
     84         return new SecP192K1FieldElement(z);
     85     }
     86 
     87     public ECFieldElement multiply(ECFieldElement b)
     88     {
     89         int[] z = Nat192.create();
     90         SecP192K1Field.multiply(x, ((SecP192K1FieldElement)b).x, z);
     91         return new SecP192K1FieldElement(z);
     92     }
     93 
     94     public ECFieldElement divide(ECFieldElement b)
     95     {
     96 //        return multiply(b.invert());
     97         int[] z = Nat192.create();
     98         Mod.invert(SecP192K1Field.P, ((SecP192K1FieldElement)b).x, z);
     99         SecP192K1Field.multiply(z, x, z);
    100         return new SecP192K1FieldElement(z);
    101     }
    102 
    103     public ECFieldElement negate()
    104     {
    105         int[] z = Nat192.create();
    106         SecP192K1Field.negate(x, z);
    107         return new SecP192K1FieldElement(z);
    108     }
    109 
    110     public ECFieldElement square()
    111     {
    112         int[] z = Nat192.create();
    113         SecP192K1Field.square(x, z);
    114         return new SecP192K1FieldElement(z);
    115     }
    116 
    117     public ECFieldElement invert()
    118     {
    119 //        return new SecP192K1FieldElement(toBigInteger().modInverse(Q));
    120         int[] z = Nat192.create();
    121         Mod.invert(SecP192K1Field.P, x, z);
    122         return new SecP192K1FieldElement(z);
    123     }
    124 
    125     /**
    126      * return a sqrt root - the routine verifies that the calculation returns the right value - if
    127      * none exists it returns null.
    128      */
    129     public ECFieldElement sqrt()
    130     {
    131         /*
    132          * Raise this element to the exponent 2^190 - 2^30 - 2^10 - 2^6 - 2^5 - 2^4 - 2^1
    133          *
    134          * Breaking up the exponent's binary representation into "repunits", we get:
    135          * { 159 1s } { 1 0s } { 19 1s } { 1 0s } { 3 1s } { 3 0s} { 3 1s } { 1 0s }
    136          *
    137          * Therefore we need an addition chain containing 3, 19, 159 (the lengths of the repunits)
    138          * We use: 1, 2, [3], 6, 8, 16, [19], 35, 70, 140, [159]
    139          */
    140 
    141         int[] x1 = this.x;
    142         if (Nat192.isZero(x1) || Nat192.isOne(x1))
    143         {
    144             return this;
    145         }
    146 
    147         int[] x2 = Nat192.create();
    148         SecP192K1Field.square(x1, x2);
    149         SecP192K1Field.multiply(x2, x1, x2);
    150         int[] x3 = Nat192.create();
    151         SecP192K1Field.square(x2, x3);
    152         SecP192K1Field.multiply(x3, x1, x3);
    153         int[] x6 = Nat192.create();
    154         SecP192K1Field.squareN(x3, 3, x6);
    155         SecP192K1Field.multiply(x6, x3, x6);
    156         int[] x8 = x6;
    157         SecP192K1Field.squareN(x6, 2, x8);
    158         SecP192K1Field.multiply(x8, x2, x8);
    159         int[] x16 = x2;
    160         SecP192K1Field.squareN(x8, 8, x16);
    161         SecP192K1Field.multiply(x16, x8, x16);
    162         int[] x19 = x8;
    163         SecP192K1Field.squareN(x16, 3, x19);
    164         SecP192K1Field.multiply(x19, x3, x19);
    165         int[] x35 = Nat192.create();
    166         SecP192K1Field.squareN(x19, 16, x35);
    167         SecP192K1Field.multiply(x35, x16, x35);
    168         int[] x70 = x16;
    169         SecP192K1Field.squareN(x35, 35, x70);
    170         SecP192K1Field.multiply(x70, x35, x70);
    171         int[] x140 = x35;
    172         SecP192K1Field.squareN(x70, 70, x140);
    173         SecP192K1Field.multiply(x140, x70, x140);
    174         int[] x159 = x70;
    175         SecP192K1Field.squareN(x140, 19, x159);
    176         SecP192K1Field.multiply(x159, x19, x159);
    177 
    178         int[] t1 = x159;
    179         SecP192K1Field.squareN(t1, 20, t1);
    180         SecP192K1Field.multiply(t1, x19, t1);
    181         SecP192K1Field.squareN(t1, 4, t1);
    182         SecP192K1Field.multiply(t1, x3, t1);
    183         SecP192K1Field.squareN(t1, 6, t1);
    184         SecP192K1Field.multiply(t1, x3, t1);
    185         SecP192K1Field.square(t1, t1);
    186 
    187         int[] t2 = x3;
    188         SecP192K1Field.square(t1, t2);
    189 
    190         return Nat192.eq(x1, t2) ? new SecP192K1FieldElement(t1) : null;
    191     }
    192 
    193     public boolean equals(Object other)
    194     {
    195         if (other == this)
    196         {
    197             return true;
    198         }
    199 
    200         if (!(other instanceof SecP192K1FieldElement))
    201         {
    202             return false;
    203         }
    204 
    205         SecP192K1FieldElement o = (SecP192K1FieldElement)other;
    206         return Nat192.eq(x, o.x);
    207     }
    208 
    209     public int hashCode()
    210     {
    211         return Q.hashCode() ^ Arrays.hashCode(x, 0, 6);
    212     }
    213 }
    214