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

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Curve25519 library for Java

There is a newer version: 0.5.0

package org.whispersystems.curve25519.java;

public class fe_frombytes {

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

public static long load_3(byte[] in, int index)
{
  long result;
  result = ((long) in[index + 0]) & 0xFF;
  result |= (((long) in[index + 1]) << 8) & 0xFF00;
  result |= (((long) in[index + 2]) << 16) & 0xFF0000;
  return result;
}

public static long load_4(byte[] in, int index)
{
  long result;
  result = (((long) in[index + 0]) & 0xFF);
  result |= ((((long) in[index + 1]) << 8) & 0xFF00);
  result |= ((((long) in[index + 2]) << 16) & 0xFF0000);
  result |= ((((long) in[index + 3]) << 24) & 0xFF000000L);
  return result;
}

/*
Ignores top bit of h.
*/

public static void fe_frombytes(int[] h,byte[] s)
{
  long h0 = load_4(s, 0);
  long h1 = load_3(s, 4) << 6;
  long h2 = load_3(s, 7) << 5;
  long h3 = load_3(s, 10) << 3;
  long h4 = load_3(s, 13) << 2;
  long h5 = load_4(s, 16);
  long h6 = load_3(s, 20) << 7;
  long h7 = load_3(s, 23) << 5;
  long h8 = load_3(s, 26) << 4;
  long h9 = (load_3(s, 29) & 8388607) << 2;
  long carry0;
  long carry1;
  long carry2;
  long carry3;
  long carry4;
  long carry5;
  long carry6;
  long carry7;
  long carry8;
  long carry9;

  carry9 = (h9 + (long) (1<<24)) >> 25; h0 += carry9 * 19; h9 -= carry9 << 25;
  carry1 = (h1 + (long) (1<<24)) >> 25; h2 += carry1; h1 -= carry1 << 25;
  carry3 = (h3 + (long) (1<<24)) >> 25; h4 += carry3; h3 -= carry3 << 25;
  carry5 = (h5 + (long) (1<<24)) >> 25; h6 += carry5; h5 -= carry5 << 25;
  carry7 = (h7 + (long) (1<<24)) >> 25; h8 += carry7; h7 -= carry7 << 25;

  carry0 = (h0 + (long) (1<<25)) >> 26; h1 += carry0; h0 -= carry0 << 26;
  carry2 = (h2 + (long) (1<<25)) >> 26; h3 += carry2; h2 -= carry2 << 26;
  carry4 = (h4 + (long) (1<<25)) >> 26; h5 += carry4; h4 -= carry4 << 26;
  carry6 = (h6 + (long) (1<<25)) >> 26; h7 += carry6; h6 -= carry6 << 26;
  carry8 = (h8 + (long) (1<<25)) >> 26; h9 += carry8; h8 -= carry8 << 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;
}


}