org.whispersystems.curve25519.java.fe_sq2 Maven / Gradle / Ivy

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Curve25519 library for Java
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package org.whispersystems.curve25519.java;

public class fe_sq2 {

//CONVERT #include "fe.h"
//CONVERT #include "long.h"

/*
h = 2 * f * f
Can overlap h with f.

Preconditions:
   |f| bounded by 1.65*2^26,1.65*2^25,1.65*2^26,1.65*2^25,etc.

Postconditions:
   |h| bounded by 1.01*2^25,1.01*2^24,1.01*2^25,1.01*2^24,etc.
*/

/*
See fe_mul.c for discussion of implementation strategy.
*/

    public static void fe_sq2(int[] h, int[] f) {
        int f0 = f[0];
        int f1 = f[1];
        int f2 = f[2];
        int f3 = f[3];
        int f4 = f[4];
        int f5 = f[5];
        int f6 = f[6];
        int f7 = f[7];
        int f8 = f[8];
        int f9 = f[9];
        int f0_2 = 2 * f0;
        int f1_2 = 2 * f1;
        int f2_2 = 2 * f2;
        int f3_2 = 2 * f3;
        int f4_2 = 2 * f4;
        int f5_2 = 2 * f5;
        int f6_2 = 2 * f6;
        int f7_2 = 2 * f7;
        int f5_38 = 38 * f5; /* 1.959375*2^30 */
        int f6_19 = 19 * f6; /* 1.959375*2^30 */
        int f7_38 = 38 * f7; /* 1.959375*2^30 */
        int f8_19 = 19 * f8; /* 1.959375*2^30 */
        int f9_38 = 38 * f9; /* 1.959375*2^30 */
        long f0f0 = f0 * (long) f0;
        long f0f1_2 = f0_2 * (long) f1;
        long f0f2_2 = f0_2 * (long) f2;
        long f0f3_2 = f0_2 * (long) f3;
        long f0f4_2 = f0_2 * (long) f4;
        long f0f5_2 = f0_2 * (long) f5;
        long f0f6_2 = f0_2 * (long) f6;
        long f0f7_2 = f0_2 * (long) f7;
        long f0f8_2 = f0_2 * (long) f8;
        long f0f9_2 = f0_2 * (long) f9;
        long f1f1_2 = f1_2 * (long) f1;
        long f1f2_2 = f1_2 * (long) f2;
        long f1f3_4 = f1_2 * (long) f3_2;
        long f1f4_2 = f1_2 * (long) f4;
        long f1f5_4 = f1_2 * (long) f5_2;
        long f1f6_2 = f1_2 * (long) f6;
        long f1f7_4 = f1_2 * (long) f7_2;
        long f1f8_2 = f1_2 * (long) f8;
        long f1f9_76 = f1_2 * (long) f9_38;
        long f2f2 = f2 * (long) f2;
        long f2f3_2 = f2_2 * (long) f3;
        long f2f4_2 = f2_2 * (long) f4;
        long f2f5_2 = f2_2 * (long) f5;
        long f2f6_2 = f2_2 * (long) f6;
        long f2f7_2 = f2_2 * (long) f7;
        long f2f8_38 = f2_2 * (long) f8_19;
        long f2f9_38 = f2 * (long) f9_38;
        long f3f3_2 = f3_2 * (long) f3;
        long f3f4_2 = f3_2 * (long) f4;
        long f3f5_4 = f3_2 * (long) f5_2;
        long f3f6_2 = f3_2 * (long) f6;
        long f3f7_76 = f3_2 * (long) f7_38;
        long f3f8_38 = f3_2 * (long) f8_19;
        long f3f9_76 = f3_2 * (long) f9_38;
        long f4f4 = f4 * (long) f4;
        long f4f5_2 = f4_2 * (long) f5;
        long f4f6_38 = f4_2 * (long) f6_19;
        long f4f7_38 = f4 * (long) f7_38;
        long f4f8_38 = f4_2 * (long) f8_19;
        long f4f9_38 = f4 * (long) f9_38;
        long f5f5_38 = f5 * (long) f5_38;
        long f5f6_38 = f5_2 * (long) f6_19;
        long f5f7_76 = f5_2 * (long) f7_38;
        long f5f8_38 = f5_2 * (long) f8_19;
        long f5f9_76 = f5_2 * (long) f9_38;
        long f6f6_19 = f6 * (long) f6_19;
        long f6f7_38 = f6 * (long) f7_38;
        long f6f8_38 = f6_2 * (long) f8_19;
        long f6f9_38 = f6 * (long) f9_38;
        long f7f7_38 = f7 * (long) f7_38;
        long f7f8_38 = f7_2 * (long) f8_19;
        long f7f9_76 = f7_2 * (long) f9_38;
        long f8f8_19 = f8 * (long) f8_19;
        long f8f9_38 = f8 * (long) f9_38;
        long f9f9_38 = f9 * (long) f9_38;
        long h0 = f0f0 + f1f9_76 + f2f8_38 + f3f7_76 + f4f6_38 + f5f5_38;
        long h1 = f0f1_2 + f2f9_38 + f3f8_38 + f4f7_38 + f5f6_38;
        long h2 = f0f2_2 + f1f1_2 + f3f9_76 + f4f8_38 + f5f7_76 + f6f6_19;
        long h3 = f0f3_2 + f1f2_2 + f4f9_38 + f5f8_38 + f6f7_38;
        long h4 = f0f4_2 + f1f3_4 + f2f2 + f5f9_76 + f6f8_38 + f7f7_38;
        long h5 = f0f5_2 + f1f4_2 + f2f3_2 + f6f9_38 + f7f8_38;
        long h6 = f0f6_2 + f1f5_4 + f2f4_2 + f3f3_2 + f7f9_76 + f8f8_19;
        long h7 = f0f7_2 + f1f6_2 + f2f5_2 + f3f4_2 + f8f9_38;
        long h8 = f0f8_2 + f1f7_4 + f2f6_2 + f3f5_4 + f4f4 + f9f9_38;
        long h9 = f0f9_2 + f1f8_2 + f2f7_2 + f3f6_2 + f4f5_2;
        long carry0;
        long carry1;
        long carry2;
        long carry3;
        long carry4;
        long carry5;
        long carry6;
        long carry7;
        long carry8;
        long carry9;

        h0 += h0;
        h1 += h1;
        h2 += h2;
        h3 += h3;
        h4 += h4;
        h5 += h5;
        h6 += h6;
        h7 += h7;
        h8 += h8;
        h9 += h9;

        carry0 = (h0 + (long) (1 << 25)) >> 26;
        h1 += carry0;
        h0 -= carry0 << 26;
        carry4 = (h4 + (long) (1 << 25)) >> 26;
        h5 += carry4;
        h4 -= carry4 << 26;

        carry1 = (h1 + (long) (1 << 24)) >> 25;
        h2 += carry1;
        h1 -= carry1 << 25;
        carry5 = (h5 + (long) (1 << 24)) >> 25;
        h6 += carry5;
        h5 -= carry5 << 25;

        carry2 = (h2 + (long) (1 << 25)) >> 26;
        h3 += carry2;
        h2 -= carry2 << 26;
        carry6 = (h6 + (long) (1 << 25)) >> 26;
        h7 += carry6;
        h6 -= carry6 << 26;

        carry3 = (h3 + (long) (1 << 24)) >> 25;
        h4 += carry3;
        h3 -= carry3 << 25;
        carry7 = (h7 + (long) (1 << 24)) >> 25;
        h8 += carry7;
        h7 -= carry7 << 25;

        carry4 = (h4 + (long) (1 << 25)) >> 26;
        h5 += carry4;
        h4 -= carry4 << 26;
        carry8 = (h8 + (long) (1 << 25)) >> 26;
        h9 += carry8;
        h8 -= carry8 << 26;

        carry9 = (h9 + (long) (1 << 24)) >> 25;
        h0 += carry9 * 19;
        h9 -= carry9 << 25;

        carry0 = (h0 + (long) (1 << 25)) >> 26;
        h1 += carry0;
        h0 -= carry0 << 26;

        h[0] = (int) h0;
        h[1] = (int) h1;
        h[2] = (int) h2;
        h[3] = (int) h3;
        h[4] = (int) h4;
        h[5] = (int) h5;
        h[6] = (int) h6;
        h[7] = (int) h7;
        h[8] = (int) h8;
        h[9] = (int) h9;
    }


}