1package org.bouncycastle.math.ec.custom.sec;
2
3import java.math.BigInteger;
4
5import org.bouncycastle.math.ec.ECFieldElement;
6import org.bouncycastle.math.raw.Mod;
7import org.bouncycastle.math.raw.Nat;
8import org.bouncycastle.util.Arrays;
9
10public class SecP521R1FieldElement extends ECFieldElement
11{
12    public static final BigInteger Q = SecP521R1Curve.q;
13
14    protected int[] x;
15
16    public SecP521R1FieldElement(BigInteger x)
17    {
18        if (x == null || x.signum() < 0 || x.compareTo(Q) >= 0)
19        {
20            throw new IllegalArgumentException("x value invalid for SecP521R1FieldElement");
21        }
22
23        this.x = SecP521R1Field.fromBigInteger(x);
24    }
25
26    public SecP521R1FieldElement()
27    {
28        this.x = Nat.create(17);
29    }
30
31    protected SecP521R1FieldElement(int[] x)
32    {
33        this.x = x;
34    }
35
36    public boolean isZero()
37    {
38        return Nat.isZero(17, x);
39    }
40
41    public boolean isOne()
42    {
43        return Nat.isOne(17, x);
44    }
45
46    public boolean testBitZero()
47    {
48        return Nat.getBit(x, 0) == 1;
49    }
50
51    public BigInteger toBigInteger()
52    {
53        return Nat.toBigInteger(17, x);
54    }
55
56    public String getFieldName()
57    {
58        return "SecP521R1Field";
59    }
60
61    public int getFieldSize()
62    {
63        return Q.bitLength();
64    }
65
66    public ECFieldElement add(ECFieldElement b)
67    {
68        int[] z = Nat.create(17);
69        SecP521R1Field.add(x, ((SecP521R1FieldElement)b).x, z);
70        return new SecP521R1FieldElement(z);
71    }
72
73    public ECFieldElement addOne()
74    {
75        int[] z = Nat.create(17);
76        SecP521R1Field.addOne(x, z);
77        return new SecP521R1FieldElement(z);
78    }
79
80    public ECFieldElement subtract(ECFieldElement b)
81    {
82        int[] z = Nat.create(17);
83        SecP521R1Field.subtract(x, ((SecP521R1FieldElement)b).x, z);
84        return new SecP521R1FieldElement(z);
85    }
86
87    public ECFieldElement multiply(ECFieldElement b)
88    {
89        int[] z = Nat.create(17);
90        SecP521R1Field.multiply(x, ((SecP521R1FieldElement)b).x, z);
91        return new SecP521R1FieldElement(z);
92    }
93
94    public ECFieldElement divide(ECFieldElement b)
95    {
96//        return multiply(b.invert());
97        int[] z = Nat.create(17);
98        Mod.invert(SecP521R1Field.P, ((SecP521R1FieldElement)b).x, z);
99        SecP521R1Field.multiply(z, x, z);
100        return new SecP521R1FieldElement(z);
101    }
102
103    public ECFieldElement negate()
104    {
105        int[] z = Nat.create(17);
106        SecP521R1Field.negate(x, z);
107        return new SecP521R1FieldElement(z);
108    }
109
110    public ECFieldElement square()
111    {
112        int[] z = Nat.create(17);
113        SecP521R1Field.square(x, z);
114        return new SecP521R1FieldElement(z);
115    }
116
117    public ECFieldElement invert()
118    {
119//        return new SecP521R1FieldElement(toBigInteger().modInverse(Q));
120        int[] z = Nat.create(17);
121        Mod.invert(SecP521R1Field.P, x, z);
122        return new SecP521R1FieldElement(z);
123    }
124
125    // D.1.4 91
126    /**
127     * return a sqrt root - the routine verifies that the calculation returns the right value - if
128     * none exists it returns null.
129     */
130    public ECFieldElement sqrt()
131    {
132        // Raise this element to the exponent 2^519
133
134        int[] x1 = this.x;
135        if (Nat.isZero(17, x1) || Nat.isOne(17, x1))
136        {
137            return this;
138        }
139
140        int[] t1 = Nat.create(17);
141        int[] t2 = Nat.create(17);
142
143        SecP521R1Field.squareN(x1, 519, t1);
144        SecP521R1Field.square(t1, t2);
145
146        return Nat.eq(17, x1, t2) ? new SecP521R1FieldElement(t1) : null;
147    }
148
149    public boolean equals(Object other)
150    {
151        if (other == this)
152        {
153            return true;
154        }
155
156        if (!(other instanceof SecP521R1FieldElement))
157        {
158            return false;
159        }
160
161        SecP521R1FieldElement o = (SecP521R1FieldElement)other;
162        return Nat.eq(17, x, o.x);
163    }
164
165    public int hashCode()
166    {
167        return Q.hashCode() ^ Arrays.hashCode(x, 0, 17);
168    }
169}
170