/*
chacha-merged.c version 20080118
D. J. Bernstein
Public domain.
*/

#include "ecrypt-sync.h"
#include "ecrypt-portable.h"

#define ROTATE(v,c) (ROTL32(v,c))
#define XOR(v,w) ((v) ^ (w))
#define PLUS(v,w) (U32V((v) + (w)))
#define PLUSONE(v) (PLUS((v),1))

#define QUARTERROUND(a,b,c,d) \
  a = PLUS(a,b); d = ROTATE(XOR(d,a),16); \
  c = PLUS(c,d); b = ROTATE(XOR(b,c),12); \
  a = PLUS(a,b); d = ROTATE(XOR(d,a), 8); \
  c = PLUS(c,d); b = ROTATE(XOR(b,c), 7);

void ECRYPT_init(void)
{
  return;
}

static const char sigma[16] = "expand 32-byte k";
static const char tau[16] = "expand 16-byte k";

void ECRYPT_keysetup(ECRYPT_ctx *x,const u8 *k,u32 kbits,u32 ivbits)
{
  (void)ivbits;
  const char *constants = NULL;

  x->input[4] = U8TO32_LITTLE(k + 0);
  x->input[5] = U8TO32_LITTLE(k + 4);
  x->input[6] = U8TO32_LITTLE(k + 8);
  x->input[7] = U8TO32_LITTLE(k + 12);
  if (kbits == 256) { /* recommended */
    k += 16;
    constants = sigma;
  } else { /* kbits == 128 */
    constants = tau;
  }
  x->input[8] = U8TO32_LITTLE(k + 0);
  x->input[9] = U8TO32_LITTLE(k + 4);
  x->input[10] = U8TO32_LITTLE(k + 8);
  x->input[11] = U8TO32_LITTLE(k + 12);
  x->input[0] = U8TO32_LITTLE(constants + 0);
  x->input[1] = U8TO32_LITTLE(constants + 4);
  x->input[2] = U8TO32_LITTLE(constants + 8);
  x->input[3] = U8TO32_LITTLE(constants + 12);
}

void ECRYPT_ivsetup(ECRYPT_ctx *x,const u8 *iv)
{
  x->input[12] = 0;
  x->input[13] = 0;
  x->input[14] = U8TO32_LITTLE(iv + 0);
  x->input[15] = U8TO32_LITTLE(iv + 4);
}

void ECRYPT_encrypt_bytes(ECRYPT_ctx *x,const u8 *m,u8 *c,u32 bytes)
{
  u32 x0 = 0, x1 = 0, x2 = 0, x3 = 0, x4 = 0, x5 = 0, x6 = 0, x7 = 0, x8 = 0, x9 = 0, x10 = 0, x11 = 0, x12 = 0, x13 = 0, x14 = 0, x15 = 0;
  u32 j0 = 0, j1 = 0, j2 = 0, j3 = 0, j4 = 0, j5 = 0, j6 = 0, j7 = 0, j8 = 0, j9 = 0, j10 = 0, j11 = 0, j12 = 0, j13 = 0, j14 = 0, j15 = 0;
  u8 *ctarget = 0;
  u8 tmp[64] = {0};
  int i = 0;

  if (!bytes) return;

  j0 = x->input[0];
  j1 = x->input[1];
  j2 = x->input[2];
  j3 = x->input[3];
  j4 = x->input[4];
  j5 = x->input[5];
  j6 = x->input[6];
  j7 = x->input[7];
  j8 = x->input[8];
  j9 = x->input[9];
  j10 = x->input[10];
  j11 = x->input[11];
  j12 = x->input[12];
  j13 = x->input[13];
  j14 = x->input[14];
  j15 = x->input[15];

  for (;;) {
    if (bytes < 64) {
      for (i = 0;i < (int)bytes;++i) tmp[i] = m[i];
      m = tmp;
      ctarget = c;
      c = tmp;
    }
    x0 = j0;
    x1 = j1;
    x2 = j2;
    x3 = j3;
    x4 = j4;
    x5 = j5;
    x6 = j6;
    x7 = j7;
    x8 = j8;
    x9 = j9;
    x10 = j10;
    x11 = j11;
    x12 = j12;
    x13 = j13;
    x14 = j14;
    x15 = j15;
    for (i = 20;i > 0;i -= 2) {
      QUARTERROUND( x0, x4, x8,x12)
      QUARTERROUND( x1, x5, x9,x13)
      QUARTERROUND( x2, x6,x10,x14)
      QUARTERROUND( x3, x7,x11,x15)
      QUARTERROUND( x0, x5,x10,x15)
      QUARTERROUND( x1, x6,x11,x12)
      QUARTERROUND( x2, x7, x8,x13)
      QUARTERROUND( x3, x4, x9,x14)
    }
    x0 = PLUS(x0,j0);
    x1 = PLUS(x1,j1);
    x2 = PLUS(x2,j2);
    x3 = PLUS(x3,j3);
    x4 = PLUS(x4,j4);
    x5 = PLUS(x5,j5);
    x6 = PLUS(x6,j6);
    x7 = PLUS(x7,j7);
    x8 = PLUS(x8,j8);
    x9 = PLUS(x9,j9);
    x10 = PLUS(x10,j10);
    x11 = PLUS(x11,j11);
    x12 = PLUS(x12,j12);
    x13 = PLUS(x13,j13);
    x14 = PLUS(x14,j14);
    x15 = PLUS(x15,j15);

    x0 = XOR(x0,U8TO32_LITTLE(m + 0));
    x1 = XOR(x1,U8TO32_LITTLE(m + 4));
    x2 = XOR(x2,U8TO32_LITTLE(m + 8));
    x3 = XOR(x3,U8TO32_LITTLE(m + 12));
    x4 = XOR(x4,U8TO32_LITTLE(m + 16));
    x5 = XOR(x5,U8TO32_LITTLE(m + 20));
    x6 = XOR(x6,U8TO32_LITTLE(m + 24));
    x7 = XOR(x7,U8TO32_LITTLE(m + 28));
    x8 = XOR(x8,U8TO32_LITTLE(m + 32));
    x9 = XOR(x9,U8TO32_LITTLE(m + 36));
    x10 = XOR(x10,U8TO32_LITTLE(m + 40));
    x11 = XOR(x11,U8TO32_LITTLE(m + 44));
    x12 = XOR(x12,U8TO32_LITTLE(m + 48));
    x13 = XOR(x13,U8TO32_LITTLE(m + 52));
    x14 = XOR(x14,U8TO32_LITTLE(m + 56));
    x15 = XOR(x15,U8TO32_LITTLE(m + 60));

    j12 = PLUSONE(j12);
    if (!j12) {
      j13 = PLUSONE(j13);
      /* stopping at 2^70 bytes per nonce is user's responsibility */
    }

    U32TO8_LITTLE(c + 0,x0);
    U32TO8_LITTLE(c + 4,x1);
    U32TO8_LITTLE(c + 8,x2);
    U32TO8_LITTLE(c + 12,x3);
    U32TO8_LITTLE(c + 16,x4);
    U32TO8_LITTLE(c + 20,x5);
    U32TO8_LITTLE(c + 24,x6);
    U32TO8_LITTLE(c + 28,x7);
    U32TO8_LITTLE(c + 32,x8);
    U32TO8_LITTLE(c + 36,x9);
    U32TO8_LITTLE(c + 40,x10);
    U32TO8_LITTLE(c + 44,x11);
    U32TO8_LITTLE(c + 48,x12);
    U32TO8_LITTLE(c + 52,x13);
    U32TO8_LITTLE(c + 56,x14);
    U32TO8_LITTLE(c + 60,x15);

    if (bytes <= 64) {
      if (bytes < 64) {
        for (i = 0;i < (int)bytes;++i) ctarget[i] = c[i];
      }
      x->input[12] = j12;
      x->input[13] = j13;
      return;
    }
    bytes -= 64;
    c += 64;
    m += 64;
  }
}

void ECRYPT_decrypt_bytes(ECRYPT_ctx *x,const u8 *c,u8 *m,u32 bytes)
{
  ECRYPT_encrypt_bytes(x,c,m,bytes);
}

void ECRYPT_keystream_bytes(ECRYPT_ctx *x,u8 *stream,u32 bytes)
{
  u32 i = 0;
  for (i = 0;i < bytes;++i) stream[i] = 0;
  ECRYPT_encrypt_bytes(x,stream,stream,bytes);
}

void hchacha20(ECRYPT_ctx *x,u8 *c)
{
  u32 x0 = 0, x1 = 0, x2 = 0, x3 = 0, x4 = 0, x5 = 0, x6 = 0, x7 = 0, x8 = 0, x9 = 0, x10 = 0, x11 = 0, x12 = 0, x13 = 0, x14 = 0, x15 = 0;
  int i = 0;

  x0 = x->input[0];
  x1 = x->input[1];
  x2 = x->input[2];
  x3 = x->input[3];
  x4 = x->input[4];
  x5 = x->input[5];
  x6 = x->input[6];
  x7 = x->input[7];
  x8 = x->input[8];
  x9 = x->input[9];
  x10 = x->input[10];
  x11 = x->input[11];
  x12 = x->input[12];
  x13 = x->input[13];
  x14 = x->input[14];
  x15 = x->input[15];

    for (i = 20;i > 0;i -= 2) {
      QUARTERROUND( x0, x4, x8,x12)
      QUARTERROUND( x1, x5, x9,x13)
      QUARTERROUND( x2, x6,x10,x14)
      QUARTERROUND( x3, x7,x11,x15)
      QUARTERROUND( x0, x5,x10,x15)
      QUARTERROUND( x1, x6,x11,x12)
      QUARTERROUND( x2, x7, x8,x13)
      QUARTERROUND( x3, x4, x9,x14)
    }

    U32TO8_LITTLE(c + 0,x0);
    U32TO8_LITTLE(c + 4,x1);
    U32TO8_LITTLE(c + 8,x2);
    U32TO8_LITTLE(c + 12,x3);
    U32TO8_LITTLE(c + 16,x12);
    U32TO8_LITTLE(c + 20,x13);
    U32TO8_LITTLE(c + 24,x14);
    U32TO8_LITTLE(c + 28,x15);
}
