1d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Rootpackage org.bouncycastle.math.ec.custom.sec;
2d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
3d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Rootimport java.math.BigInteger;
4d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
5d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Rootimport org.bouncycastle.math.ec.ECFieldElement;
6d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Rootimport org.bouncycastle.math.raw.Mod;
7d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Rootimport org.bouncycastle.math.raw.Nat256;
8d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Rootimport org.bouncycastle.util.Arrays;
9d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
10d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Rootpublic class SecP256R1FieldElement extends ECFieldElement
11d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root{
12d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public static final BigInteger Q = SecP256R1Curve.q;
13d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
14d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    protected int[] x;
15d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
16d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public SecP256R1FieldElement(BigInteger x)
17d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
18d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        if (x == null || x.signum() < 0 || x.compareTo(Q) >= 0)
19d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        {
20d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root            throw new IllegalArgumentException("x value invalid for SecP256R1FieldElement");
21d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        }
22d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
23d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        this.x = SecP256R1Field.fromBigInteger(x);
24d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
25d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
26d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public SecP256R1FieldElement()
27d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
28d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        this.x = Nat256.create();
29d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
30d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
31d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    protected SecP256R1FieldElement(int[] x)
32d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
33d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        this.x = x;
34d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
35d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
36d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public boolean isZero()
37d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
38d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return Nat256.isZero(x);
39d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
40d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
41d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public boolean isOne()
42d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
43d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return Nat256.isOne(x);
44d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
45d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
46d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public boolean testBitZero()
47d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
48d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return Nat256.getBit(x, 0) == 1;
49d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
50d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
51d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public BigInteger toBigInteger()
52d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
53d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return Nat256.toBigInteger(x);
54d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
55d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
56d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public String getFieldName()
57d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
58d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return "SecP256R1Field";
59d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
60d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
61d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public int getFieldSize()
62d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
63d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return Q.bitLength();
64d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
65d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
66d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public ECFieldElement add(ECFieldElement b)
67d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
68d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        int[] z = Nat256.create();
69d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.add(x, ((SecP256R1FieldElement)b).x, z);
70d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return new SecP256R1FieldElement(z);
71d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
72d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
73d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public ECFieldElement addOne()
74d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
75d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        int[] z = Nat256.create();
76d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.addOne(x, z);
77d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return new SecP256R1FieldElement(z);
78d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
79d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
80d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public ECFieldElement subtract(ECFieldElement b)
81d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
82d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        int[] z = Nat256.create();
83d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.subtract(x, ((SecP256R1FieldElement)b).x, z);
84d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return new SecP256R1FieldElement(z);
85d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
86d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
87d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public ECFieldElement multiply(ECFieldElement b)
88d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
89d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        int[] z = Nat256.create();
90d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.multiply(x, ((SecP256R1FieldElement)b).x, z);
91d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return new SecP256R1FieldElement(z);
92d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
93d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
94d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public ECFieldElement divide(ECFieldElement b)
95d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
96d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root//        return multiply(b.invert());
97d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        int[] z = Nat256.create();
98d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        Mod.invert(SecP256R1Field.P, ((SecP256R1FieldElement)b).x, z);
99d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.multiply(z, x, z);
100d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return new SecP256R1FieldElement(z);
101d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
102d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
103d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public ECFieldElement negate()
104d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
105d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        int[] z = Nat256.create();
106d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.negate(x, z);
107d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return new SecP256R1FieldElement(z);
108d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
109d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
110d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public ECFieldElement square()
111d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
112d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        int[] z = Nat256.create();
113d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.square(x, z);
114d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return new SecP256R1FieldElement(z);
115d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
116d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
117d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public ECFieldElement invert()
118d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
119d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root//        return new SecP256R1FieldElement(toBigInteger().modInverse(Q));
120d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        int[] z = Nat256.create();
121d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        Mod.invert(SecP256R1Field.P, x, z);
122d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return new SecP256R1FieldElement(z);
123d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
124d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
125d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    /**
126d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root     * return a sqrt root - the routine verifies that the calculation returns the right value - if
127d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root     * none exists it returns null.
128d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root     */
129d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public ECFieldElement sqrt()
130d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
131d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        // Raise this element to the exponent 2^254 - 2^222 + 2^190 + 2^94
132d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
133d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        int[] x1 = this.x;
134d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        if (Nat256.isZero(x1) || Nat256.isOne(x1))
135d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        {
136d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root            return this;
137d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        }
138d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
139d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        int[] t1 = Nat256.create();
140d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        int[] t2 = Nat256.create();
141d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
142d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.square(x1, t1);
143d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.multiply(t1, x1, t1);
144d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
145d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.squareN(t1, 2, t2);
146d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.multiply(t2, t1, t2);
147d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
148d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.squareN(t2, 4, t1);
149d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.multiply(t1, t2, t1);
150d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
151d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.squareN(t1, 8, t2);
152d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.multiply(t2, t1, t2);
153d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
154d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.squareN(t2, 16, t1);
155d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.multiply(t1, t2, t1);
156d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
157d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.squareN(t1, 32, t1);
158d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.multiply(t1, x1, t1);
159d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
160d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.squareN(t1, 96, t1);
161d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.multiply(t1, x1, t1);
162d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
163d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.squareN(t1, 94, t1);
164d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1Field.square(t1, t2);
165d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
166d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return Nat256.eq(x1, t2) ? new SecP256R1FieldElement(t1) : null;
167d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
168d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
169d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public boolean equals(Object other)
170d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
171d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        if (other == this)
172d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        {
173d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root            return true;
174d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        }
175d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
176d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        if (!(other instanceof SecP256R1FieldElement))
177d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        {
178d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root            return false;
179d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        }
180d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
181d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        SecP256R1FieldElement o = (SecP256R1FieldElement)other;
182d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return Nat256.eq(x, o.x);
183d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
184d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root
185d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    public int hashCode()
186d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    {
187d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root        return Q.hashCode() ^ Arrays.hashCode(x, 0, 8);
188d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root    }
189d001700a15b8bd733ae344c1fc315b97c43c6590Kenny Root}
190