tweetnacl.c

/*
    Copyright (c) 2016 Contributors as noted in the AUTHORS file

    This file is part of libzmq, the ZeroMQ core engine in C++.

    libzmq is free software; you can redistribute it and/or modify it under
    the terms of the GNU Lesser General Public License (LGPL) as published
    by the Free Software Foundation; either version 3 of the License, or
    (at your option) any later version.

    As a special exception, the Contributors give you permission to link
    this library with independent modules to produce an executable,
    regardless of the license terms of these independent modules, and to
    copy and distribute the resulting executable under terms of your choice,
    provided that you also meet, for each linked independent module, the
    terms and conditions of the license of that module. An independent
    module is a module which is not derived from or based on this library.
    If you modify this library, you must extend this exception to your
    version of the library.

    libzmq is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
    License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "platform.hpp"
#if defined (ZMQ_USE_TWEETNACL)

/*
    Disable warnings for this source only, rather than for the whole
    codebase when building with C99 (gcc >= 4.2) or with Microsoft's compiler
*/
#if defined __GNUC__ && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 2)) && __STDC_VERSION__ < 201112L
#   pragma GCC diagnostic ignored "-Wsign-compare"
#elif defined _MSC_VER
#   pragma warning (disable:4018 4244 4146)
#endif

#include "tweetnacl.h"

#define FOR(i,n) for (i = 0;i < n;++i)
#define sv static void

static const u8
  _0[16],
  _9[32] = {9};
static const gf
  gf0,
  gf1 = {1},
  _121665 = {0xDB41,1},
  D = {0x78a3, 0x1359, 0x4dca, 0x75eb, 0xd8ab, 0x4141, 0x0a4d, 0x0070, 0xe898, 0x7779, 0x4079, 0x8cc7, 0xfe73, 0x2b6f, 0x6cee, 0x5203},
  D2 = {0xf159, 0x26b2, 0x9b94, 0xebd6, 0xb156, 0x8283, 0x149a, 0x00e0, 0xd130, 0xeef3, 0x80f2, 0x198e, 0xfce7, 0x56df, 0xd9dc, 0x2406},
  X = {0xd51a, 0x8f25, 0x2d60, 0xc956, 0xa7b2, 0x9525, 0xc760, 0x692c, 0xdc5c, 0xfdd6, 0xe231, 0xc0a4, 0x53fe, 0xcd6e, 0x36d3, 0x2169},
  Y = {0x6658, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666, 0x6666},
  I = {0xa0b0, 0x4a0e, 0x1b27, 0xc4ee, 0xe478, 0xad2f, 0x1806, 0x2f43, 0xd7a7, 0x3dfb, 0x0099, 0x2b4d, 0xdf0b, 0x4fc1, 0x2480, 0x2b83};

static u32 L32(u32 x,int c) { return (x << c) | ((x&0xffffffff) >> (32 - c)); }

static u32 ld32(const u8 *x)
{
  u32 u = x[3];
  u = (u<<8)|x[2];
  u = (u<<8)|x[1];
  return (u<<8)|x[0];
}

static u64 dl64(const u8 *x)
{
  u64 i,u=0;
  FOR(i,8) u=(u<<8)|x[i];
  return u;
}

sv st32(u8 *x,u32 u)
{
  int i;
  FOR(i,4) { x[i] = u; u >>= 8; }
}

sv ts64(u8 *x,u64 u)
{
  int i;
  for (i = 7;i >= 0;--i) { x[i] = u; u >>= 8; }
}

static int vn(const u8 *x,const u8 *y,int n)
{
  u32 i,d = 0;
  FOR(i,n) d |= x[i]^y[i];
  return (1 & ((d - 1) >> 8)) - 1;
}

int crypto_verify_16(const u8 *x,const u8 *y)
{
  return vn(x,y,16);
}

int crypto_verify_32(const u8 *x,const u8 *y)
{
  return vn(x,y,32);
}

sv core(u8 *out,const u8 *in,const u8 *k,const u8 *c,int h)
{
  u32 w[16],x[16],y[16],t[4];
  int i,j,m;

  FOR(i,4) {
    x[5*i] = ld32(c+4*i);
    x[1+i] = ld32(k+4*i);
    x[6+i] = ld32(in+4*i);
    x[11+i] = ld32(k+16+4*i);
  }

  FOR(i,16) y[i] = x[i];

  FOR(i,20) {
    FOR(j,4) {
      FOR(m,4) t[m] = x[(5*j+4*m)%16];
      t[1] ^= L32(t[0]+t[3], 7);
      t[2] ^= L32(t[1]+t[0], 9);
      t[3] ^= L32(t[2]+t[1],13);
      t[0] ^= L32(t[3]+t[2],18);
      FOR(m,4) w[4*j+(j+m)%4] = t[m];
    }
    FOR(m,16) x[m] = w[m];
  }

  if (h) {
    FOR(i,16) x[i] += y[i];
    FOR(i,4) {
      x[5*i] -= ld32(c+4*i);
      x[6+i] -= ld32(in+4*i);
    }
    FOR(i,4) {
      st32(out+4*i,x[5*i]);
      st32(out+16+4*i,x[6+i]);
    }
  } else
    FOR(i,16) st32(out + 4 * i,x[i] + y[i]);
}

int crypto_core_salsa20(u8 *out,const u8 *in,const u8 *k,const u8 *c)
{
  core(out,in,k,c,0);
  return 0;
}

int crypto_core_hsalsa20(u8 *out,const u8 *in,const u8 *k,const u8 *c)
{
  core(out,in,k,c,1);
  return 0;
}

static const u8 sigma[16] = "expand 32-byte k";

int crypto_stream_salsa20_xor(u8 *c,const u8 *m,u64 b,const u8 *n,const u8 *k)
{
  u8 z[16],x[64];
  u32 u,i;
  if (!b) return 0;
  FOR(i,16) z[i] = 0;
  FOR(i,8) z[i] = n[i];
  while (b >= 64) {
    crypto_core_salsa20(x,z,k,sigma);
    FOR(i,64) c[i] = (m?m[i]:0) ^ x[i];
    u = 1;
    for (i = 8;i < 16;++i) {
      u += (u32) z[i];
      z[i] = u;
      u >>= 8;
    }
    b -= 64;
    c += 64;
    if (m) m += 64;
  }
  if (b) {
    crypto_core_salsa20(x,z,k,sigma);
    FOR(i,b) c[i] = (m?m[i]:0) ^ x[i];
  }
  return 0;
}

int crypto_stream_salsa20(u8 *c,u64 d,const u8 *n,const u8 *k)
{
  return crypto_stream_salsa20_xor(c,0,d,n,k);
}

int crypto_stream(u8 *c,u64 d,const u8 *n,const u8 *k)
{
  u8 s[32];
  crypto_core_hsalsa20(s,n,k,sigma);
  return crypto_stream_salsa20(c,d,n+16,s);
}

int crypto_stream_xor(u8 *c,const u8 *m,u64 d,const u8 *n,const u8 *k)
{
  u8 s[32];
  crypto_core_hsalsa20(s,n,k,sigma);
  return crypto_stream_salsa20_xor(c,m,d,n+16,s);
}

sv add1305(u32 *h,const u32 *c)
{
  u32 j,u = 0;
  FOR(j,17) {
    u += h[j] + c[j];
    h[j] = u & 255;
    u >>= 8;
  }
}

static const u32 minusp[17] = {
  5, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 252
} ;

int crypto_onetimeauth(u8 *out,const u8 *m,u64 n,const u8 *k)
{
  u32 s,i,j,u,x[17],r[17],h[17],c[17],g[17];

  FOR(j,17) r[j]=h[j]=0;
  FOR(j,16) r[j]=k[j];
  r[3]&=15;
  r[4]&=252;
  r[7]&=15;
  r[8]&=252;
  r[11]&=15;
  r[12]&=252;
  r[15]&=15;

  while (n > 0) {
    FOR(j,17) c[j] = 0;
    for (j = 0;(j < 16) && (j < n);++j) c[j] = m[j];
    c[j] = 1;
    m += j; n -= j;
    add1305(h,c);
    FOR(i,17) {
      x[i] = 0;
      FOR(j,17) x[i] += h[j] * ((j <= i) ? r[i - j] : 320 * r[i + 17 - j]);
    }
    FOR(i,17) h[i] = x[i];
    u = 0;
    FOR(j,16) {
      u += h[j];
      h[j] = u & 255;
      u >>= 8;
    }
    u += h[16]; h[16] = u & 3;
    u = 5 * (u >> 2);
    FOR(j,16) {
      u += h[j];
      h[j] = u & 255;
      u >>= 8;
    }
    u += h[16]; h[16] = u;
  }

  FOR(j,17) g[j] = h[j];
  add1305(h,minusp);
  s = -(h[16] >> 7);
  FOR(j,17) h[j] ^= s & (g[j] ^ h[j]);

  FOR(j,16) c[j] = k[j + 16];
  c[16] = 0;
  add1305(h,c);
  FOR(j,16) out[j] = h[j];
  return 0;
}

int crypto_onetimeauth_verify(const u8 *h,const u8 *m,u64 n,const u8 *k)
{
  u8 x[16];
  crypto_onetimeauth(x,m,n,k);
  return crypto_verify_16(h,x);
}

int crypto_secretbox(u8 *c,const u8 *m,u64 d,const u8 *n,const u8 *k)
{
  int i;
  if (d < 32) return -1;
  crypto_stream_xor(c,m,d,n,k);
  crypto_onetimeauth(c + 16,c + 32,d - 32,c);
  FOR(i,16) c[i] = 0;
  return 0;
}

int crypto_secretbox_open(u8 *m,const u8 *c,u64 d,const u8 *n,const u8 *k)
{
  int i;
  u8 x[32];
  if (d < 32) return -1;
  crypto_stream(x,32,n,k);
  if (crypto_onetimeauth_verify(c + 16,c + 32,d - 32,x) != 0) return -1;
  crypto_stream_xor(m,c,d,n,k);
  FOR(i,32) m[i] = 0;
  return 0;
}

sv set25519(gf r, const gf a)
{
  int i;
  FOR(i,16) r[i]=a[i];
}

sv car25519(gf o)
{
  int i;
  i64 c;
  FOR(i,16) {
    o[i]+=(1LL<<16);
    c=o[i]>>16;
    o[(i+1)*(i<15)]+=c-1+37*(c-1)*(i==15);
    o[i]-=c<<16;
  }
}

sv sel25519(gf p,gf q,int b)
{
  i64 t,i,c=~(b-1);
  FOR(i,16) {
    t= c&(p[i]^q[i]);
    p[i]^=t;
    q[i]^=t;
  }
}

sv pack25519(u8 *o,const gf n)
{
  int i,j,b;
  gf m,t;
  FOR(i,16) t[i]=n[i];
  car25519(t);
  car25519(t);
  car25519(t);
  FOR(j,2) {
    m[0]=t[0]-0xffed;
    for(i=1;i<15;i++) {
      m[i]=t[i]-0xffff-((m[i-1]>>16)&1);
      m[i-1]&=0xffff;
    }
    m[15]=t[15]-0x7fff-((m[14]>>16)&1);
    b=(m[15]>>16)&1;
    m[14]&=0xffff;
    sel25519(t,m,1-b);
  }
  FOR(i,16) {
    o[2*i]=t[i]&0xff;
    o[2*i+1]=t[i]>>8;
  }
}

static int neq25519(const gf a, const gf b)
{
  u8 c[32],d[32];
  pack25519(c,a);
  pack25519(d,b);
  return crypto_verify_32(c,d);
}

static u8 par25519(const gf a)
{
  u8 d[32];
  pack25519(d,a);
  return d[0]&1;
}

sv unpack25519(gf o, const u8 *n)
{
  int i;
  FOR(i,16) o[i]=n[2*i]+((i64)n[2*i+1]<<8);
  o[15]&=0x7fff;
}

sv A(gf o,const gf a,const gf b)
{
  int i;
  FOR(i,16) o[i]=a[i]+b[i];
}

sv Z(gf o,const gf a,const gf b)
{
  int i;
  FOR(i,16) o[i]=a[i]-b[i];
}

sv M(gf o,const gf a,const gf b)
{
  i64 i,j,t[31];
  FOR(i,31) t[i]=0;
  FOR(i,16) FOR(j,16) t[i+j]+=a[i]*b[j];
  FOR(i,15) t[i]+=38*t[i+16];
  FOR(i,16) o[i]=t[i];
  car25519(o);
  car25519(o);
}

sv S(gf o,const gf a)
{
  M(o,a,a);
}

sv inv25519(gf o,const gf i)
{
  gf c;
  int a;
  FOR(a,16) c[a]=i[a];
  for(a=253;a>=0;a--) {
    S(c,c);
    if(a!=2&&a!=4) M(c,c,i);
  }
  FOR(a,16) o[a]=c[a];
}

sv pow2523(gf o,const gf i)
{
  gf c;
  int a;
  FOR(a,16) c[a]=i[a];
  for(a=250;a>=0;a--) {
    S(c,c);
    if(a!=1) M(c,c,i);
  }
  FOR(a,16) o[a]=c[a];
}

int crypto_scalarmult(u8 *q,const u8 *n,const u8 *p)
{
  u8 z[32];
  i64 x[80],r,i;
  gf a,b,c,d,e,f;
  FOR(i,31) z[i]=n[i];
  z[31]=(n[31]&127)|64;
  z[0]&=248;
  unpack25519(x,p);
  FOR(i,16) {
    b[i]=x[i];
    d[i]=a[i]=c[i]=0;
  }
  a[0]=d[0]=1;
  for(i=254;i>=0;--i) {
    r=(z[i>>3]>>(i&7))&1;
    sel25519(a,b,r);
    sel25519(c,d,r);
    A(e,a,c);
    Z(a,a,c);
    A(c,b,d);
    Z(b,b,d);
    S(d,e);
    S(f,a);
    M(a,c,a);
    M(c,b,e);
    A(e,a,c);
    Z(a,a,c);
    S(b,a);
    Z(c,d,f);
    M(a,c,_121665);
    A(a,a,d);
    M(c,c,a);
    M(a,d,f);
    M(d,b,x);
    S(b,e);
    sel25519(a,b,r);
    sel25519(c,d,r);
  }
  FOR(i,16) {
    x[i+16]=a[i];
    x[i+32]=c[i];
    x[i+48]=b[i];
    x[i+64]=d[i];
  }
  inv25519(x+32,x+32);
  M(x+16,x+16,x+32);
  pack25519(q,x+16);
  return 0;
}

int crypto_scalarmult_base(u8 *q,const u8 *n)
{ 
  return crypto_scalarmult(q,n,_9);
}

int crypto_box_keypair(u8 *y,u8 *x)
{
  randombytes(x,32);
  return crypto_scalarmult_base(y,x);
}

int crypto_box_beforenm(u8 *k,const u8 *y,const u8 *x)
{
  u8 s[32];
  crypto_scalarmult(s,x,y);
  return crypto_core_hsalsa20(k,_0,s,sigma);
}

int crypto_box_afternm(u8 *c,const u8 *m,u64 d,const u8 *n,const u8 *k)
{
  return crypto_secretbox(c,m,d,n,k);
}

int crypto_box_open_afternm(u8 *m,const u8 *c,u64 d,const u8 *n,const u8 *k)
{
  return crypto_secretbox_open(m,c,d,n,k);
}

int crypto_box(u8 *c,const u8 *m,u64 d,const u8 *n,const u8 *y,const u8 *x)
{
  u8 k[32];
  crypto_box_beforenm(k,y,x);
  return crypto_box_afternm(c,m,d,n,k);
}

int crypto_box_open(u8 *m,const u8 *c,u64 d,const u8 *n,const u8 *y,const u8 *x)
{
  u8 k[32];
  crypto_box_beforenm(k,y,x);
  return crypto_box_open_afternm(m,c,d,n,k);
}

static u64 R(u64 x,int c) { return (x >> c) | (x << (64 - c)); }
static u64 Ch(u64 x,u64 y,u64 z) { return (x & y) ^ (~x & z); }
static u64 Maj(u64 x,u64 y,u64 z) { return (x & y) ^ (x & z) ^ (y & z); }
static u64 Sigma0(u64 x) { return R(x,28) ^ R(x,34) ^ R(x,39); }
static u64 Sigma1(u64 x) { return R(x,14) ^ R(x,18) ^ R(x,41); }
static u64 sigma0(u64 x) { return R(x, 1) ^ R(x, 8) ^ (x >> 7); }
static u64 sigma1(u64 x) { return R(x,19) ^ R(x,61) ^ (x >> 6); }

static const u64 K[80] = 
{
  0x428a2f98d728ae22ULL, 0x7137449123ef65cdULL, 0xb5c0fbcfec4d3b2fULL, 0xe9b5dba58189dbbcULL,
  0x3956c25bf348b538ULL, 0x59f111f1b605d019ULL, 0x923f82a4af194f9bULL, 0xab1c5ed5da6d8118ULL,
  0xd807aa98a3030242ULL, 0x12835b0145706fbeULL, 0x243185be4ee4b28cULL, 0x550c7dc3d5ffb4e2ULL,
  0x72be5d74f27b896fULL, 0x80deb1fe3b1696b1ULL, 0x9bdc06a725c71235ULL, 0xc19bf174cf692694ULL,
  0xe49b69c19ef14ad2ULL, 0xefbe4786384f25e3ULL, 0x0fc19dc68b8cd5b5ULL, 0x240ca1cc77ac9c65ULL,
  0x2de92c6f592b0275ULL, 0x4a7484aa6ea6e483ULL, 0x5cb0a9dcbd41fbd4ULL, 0x76f988da831153b5ULL,
  0x983e5152ee66dfabULL, 0xa831c66d2db43210ULL, 0xb00327c898fb213fULL, 0xbf597fc7beef0ee4ULL,
  0xc6e00bf33da88fc2ULL, 0xd5a79147930aa725ULL, 0x06ca6351e003826fULL, 0x142929670a0e6e70ULL,
  0x27b70a8546d22ffcULL, 0x2e1b21385c26c926ULL, 0x4d2c6dfc5ac42aedULL, 0x53380d139d95b3dfULL,
  0x650a73548baf63deULL, 0x766a0abb3c77b2a8ULL, 0x81c2c92e47edaee6ULL, 0x92722c851482353bULL,
  0xa2bfe8a14cf10364ULL, 0xa81a664bbc423001ULL, 0xc24b8b70d0f89791ULL, 0xc76c51a30654be30ULL,
  0xd192e819d6ef5218ULL, 0xd69906245565a910ULL, 0xf40e35855771202aULL, 0x106aa07032bbd1b8ULL,
  0x19a4c116b8d2d0c8ULL, 0x1e376c085141ab53ULL, 0x2748774cdf8eeb99ULL, 0x34b0bcb5e19b48a8ULL,
  0x391c0cb3c5c95a63ULL, 0x4ed8aa4ae3418acbULL, 0x5b9cca4f7763e373ULL, 0x682e6ff3d6b2b8a3ULL,
  0x748f82ee5defb2fcULL, 0x78a5636f43172f60ULL, 0x84c87814a1f0ab72ULL, 0x8cc702081a6439ecULL,
  0x90befffa23631e28ULL, 0xa4506cebde82bde9ULL, 0xbef9a3f7b2c67915ULL, 0xc67178f2e372532bULL,
  0xca273eceea26619cULL, 0xd186b8c721c0c207ULL, 0xeada7dd6cde0eb1eULL, 0xf57d4f7fee6ed178ULL,
  0x06f067aa72176fbaULL, 0x0a637dc5a2c898a6ULL, 0x113f9804bef90daeULL, 0x1b710b35131c471bULL,
  0x28db77f523047d84ULL, 0x32caab7b40c72493ULL, 0x3c9ebe0a15c9bebcULL, 0x431d67c49c100d4cULL,
  0x4cc5d4becb3e42b6ULL, 0x597f299cfc657e2aULL, 0x5fcb6fab3ad6faecULL, 0x6c44198c4a475817ULL
};

int crypto_hashblocks(u8 *x,const u8 *m,u64 n)
{
  u64 z[8],b[8],a[8],w[16],t;
  int i,j;

  FOR(i,8) z[i] = a[i] = dl64(x + 8 * i);

  while (n >= 128) {
    FOR(i,16) w[i] = dl64(m + 8 * i);

    FOR(i,80) {
      FOR(j,8) b[j] = a[j];
      t = a[7] + Sigma1(a[4]) + Ch(a[4],a[5],a[6]) + K[i] + w[i%16];
      b[7] = t + Sigma0(a[0]) + Maj(a[0],a[1],a[2]);
      b[3] += t;
      FOR(j,8) a[(j+1)%8] = b[j];
      if (i%16 == 15)
	FOR(j,16)
	  w[j] += w[(j+9)%16] + sigma0(w[(j+1)%16]) + sigma1(w[(j+14)%16]);
    }

    FOR(i,8) { a[i] += z[i]; z[i] = a[i]; }

    m += 128;
    n -= 128;
  }

  FOR(i,8) ts64(x+8*i,z[i]);

  return n;
}

static const u8 iv[64] = {
  0x6a,0x09,0xe6,0x67,0xf3,0xbc,0xc9,0x08,
  0xbb,0x67,0xae,0x85,0x84,0xca,0xa7,0x3b,
  0x3c,0x6e,0xf3,0x72,0xfe,0x94,0xf8,0x2b,
  0xa5,0x4f,0xf5,0x3a,0x5f,0x1d,0x36,0xf1,
  0x51,0x0e,0x52,0x7f,0xad,0xe6,0x82,0xd1,
  0x9b,0x05,0x68,0x8c,0x2b,0x3e,0x6c,0x1f,
  0x1f,0x83,0xd9,0xab,0xfb,0x41,0xbd,0x6b,
  0x5b,0xe0,0xcd,0x19,0x13,0x7e,0x21,0x79
} ;

int crypto_hash(u8 *out,const u8 *m,u64 n)
{
  u8 h[64],x[256];
  u64 i,b = n;

  FOR(i,64) h[i] = iv[i];

  crypto_hashblocks(h,m,n);
  m += n;
  n &= 127;
  m -= n;

  FOR(i,256) x[i] = 0;
  FOR(i,n) x[i] = m[i];
  x[n] = 128;

  n = 256-128*(n<112);
  x[n-9] = b >> 61;
  ts64(x+n-8,b<<3);
  crypto_hashblocks(h,x,n);

  FOR(i,64) out[i] = h[i];

  return 0;
}

sv add(gf p[4],gf q[4])
{
  gf a,b,c,d,t,e,f,g,h;
  
  Z(a, p[1], p[0]);
  Z(t, q[1], q[0]);
  M(a, a, t);
  A(b, p[0], p[1]);
  A(t, q[0], q[1]);
  M(b, b, t);
  M(c, p[3], q[3]);
  M(c, c, D2);
  M(d, p[2], q[2]);
  A(d, d, d);
  Z(e, b, a);
  Z(f, d, c);
  A(g, d, c);
  A(h, b, a);

  M(p[0], e, f);
  M(p[1], h, g);
  M(p[2], g, f);
  M(p[3], e, h);
}

sv cswap(gf p[4],gf q[4],u8 b)
{
  int i;
  FOR(i,4)
    sel25519(p[i],q[i],b);
}

sv pack(u8 *r,gf p[4])
{
  gf tx, ty, zi;
  inv25519(zi, p[2]); 
  M(tx, p[0], zi);
  M(ty, p[1], zi);
  pack25519(r, ty);
  r[31] ^= par25519(tx) << 7;
}

sv scalarmult(gf p[4],gf q[4],const u8 *s)
{
  int i;
  set25519(p[0],gf0);
  set25519(p[1],gf1);
  set25519(p[2],gf1);
  set25519(p[3],gf0);
  for (i = 255;i >= 0;--i) {
    u8 b = (s[i/8]>>(i&7))&1;
    cswap(p,q,b);
    add(q,p);
    add(p,p);
    cswap(p,q,b);
  }
}

sv scalarbase(gf p[4],const u8 *s)
{
  gf q[4];
  set25519(q[0],X);
  set25519(q[1],Y);
  set25519(q[2],gf1);
  M(q[3],X,Y);
  scalarmult(p,q,s);
}

int crypto_sign_keypair(u8 *pk, u8 *sk)
{
  u8 d[64];
  gf p[4];
  int i;

  randombytes(sk, 32);
  crypto_hash(d, sk, 32);
  d[0] &= 248;
  d[31] &= 127;
  d[31] |= 64;

  scalarbase(p,d);
  pack(pk,p);

  FOR(i,32) sk[32 + i] = pk[i];
  return 0;
}

static const u64 L[32] = {0xed, 0xd3, 0xf5, 0x5c, 0x1a, 0x63, 0x12, 0x58, 0xd6, 0x9c, 0xf7, 0xa2, 0xde, 0xf9, 0xde, 0x14, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x10};

sv modL(u8 *r,i64 x[64])
{
  i64 carry,i,j;
  for (i = 63;i >= 32;--i) {
    carry = 0;
    for (j = i - 32;j < i - 12;++j) {
      x[j] += carry - 16 * x[i] * L[j - (i - 32)];
      carry = (x[j] + 128) >> 8;
      x[j] -= carry << 8;
    }
    x[j] += carry;
    x[i] = 0;
  }
  carry = 0;
  FOR(j,32) {
    x[j] += carry - (x[31] >> 4) * L[j];
    carry = x[j] >> 8;
    x[j] &= 255;
  }
  FOR(j,32) x[j] -= carry * L[j];
  FOR(i,32) {
    x[i+1] += x[i] >> 8;
    r[i] = x[i] & 255;
  }
}

sv reduce(u8 *r)
{
  i64 x[64],i;
  FOR(i,64) x[i] = (u64) r[i];
  FOR(i,64) r[i] = 0;
  modL(r,x);
}

int crypto_sign(u8 *sm,u64 *smlen,const u8 *m,u64 n,const u8 *sk)
{
  u8 d[64],h[64],r[64];
  i64 i,j,x[64];
  gf p[4];

  crypto_hash(d, sk, 32);
  d[0] &= 248;
  d[31] &= 127;
  d[31] |= 64;

  *smlen = n+64;
  FOR(i,n) sm[64 + i] = m[i];
  FOR(i,32) sm[32 + i] = d[32 + i];

  crypto_hash(r, sm+32, n+32);
  reduce(r);
  scalarbase(p,r);
  pack(sm,p);

  FOR(i,32) sm[i+32] = sk[i+32];
  crypto_hash(h,sm,n + 64);
  reduce(h);

  FOR(i,64) x[i] = 0;
  FOR(i,32) x[i] = (u64) r[i];
  FOR(i,32) FOR(j,32) x[i+j] += h[i] * (u64) d[j];
  modL(sm + 32,x);

  return 0;
}

static int unpackneg(gf r[4],const u8 p[32])
{
  gf t, chk, num, den, den2, den4, den6;
  set25519(r[2],gf1);
  unpack25519(r[1],p);
  S(num,r[1]);
  M(den,num,D);
  Z(num,num,r[2]);
  A(den,r[2],den);

  S(den2,den);
  S(den4,den2);
  M(den6,den4,den2);
  M(t,den6,num);
  M(t,t,den);

  pow2523(t,t);
  M(t,t,num);
  M(t,t,den);
  M(t,t,den);
  M(r[0],t,den);

  S(chk,r[0]);
  M(chk,chk,den);
  if (neq25519(chk, num)) M(r[0],r[0],I);

  S(chk,r[0]);
  M(chk,chk,den);
  if (neq25519(chk, num)) return -1;

  if (par25519(r[0]) == (p[31]>>7)) Z(r[0],gf0,r[0]);

  M(r[3],r[0],r[1]);
  return 0;
}

int crypto_sign_open(u8 *m,u64 *mlen,const u8 *sm,u64 n,const u8 *pk)
{
  int i;
  u8 t[32],h[64];
  gf p[4],q[4];

  *mlen = -1;
  if (n < 64) return -1;

  if (unpackneg(q,pk)) return -1;

  FOR(i,n) m[i] = sm[i];
  FOR(i,32) m[i+32] = pk[i];
  crypto_hash(h,m,n);
  reduce(h);
  scalarmult(p,q,h);

  scalarbase(q,sm + 32);
  add(p,q);
  pack(t,p);

  n -= 64;
  if (crypto_verify_32(sm, t)) {
    FOR(i,n) m[i] = 0;
    return -1;
  }

  FOR(i,n) m[i] = sm[i + 64];
  *mlen = n;
  return 0;
}


#ifdef ZMQ_HAVE_WINDOWS

#include <windows.h>
#include <WinCrypt.h>

#define NCP ((HCRYPTPROV) 0)

HCRYPTPROV hProvider = NCP;

void randombytes(unsigned char *x,unsigned long long xlen)
{
    unsigned i;
    BOOL ret;

    if (hProvider == NCP) {
        for (;;) {
            ret = CryptAcquireContext(&hProvider, NULL, NULL,
                                      PROV_RSA_FULL, CRYPT_VERIFYCONTEXT | CRYPT_SILENT);
            if (ret != FALSE)
                break;
            Sleep (1);
        }
    }
    while (xlen > 0) {
        if (xlen < 1048576)
            i = (unsigned) xlen;
        else
            i = 1048576;

        ret = CryptGenRandom(hProvider, i, x);
        if (ret == FALSE) {
            Sleep(1);
            continue;
        }
        x += i;
        xlen -= i;
    }
}

int randombytes_close(void)
{
    int rc = -1;
    if ((hProvider != NCP) && (CryptReleaseContext(hProvider, 0) != FALSE)) {
        hProvider = NCP;
        rc = 0;
    }
    return rc;
}

#else

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>

static int fd = -1;

void randombytes (unsigned char *x,unsigned long long xlen)
{
    int i;
    if (fd == -1) {
        for (;;) {
            fd = open("/dev/urandom",O_RDONLY);
            if (fd != -1) break;
                sleep (1);
        }
    }
    while (xlen > 0) {
        if (xlen < 1048576)
            i = xlen;
        else
            i = 1048576;

        i = read(fd,x,i);
        if (i < 1) {
            sleep (1);
            continue;
        }
        x += i;
        xlen -= i;
    }
}

int randombytes_close (void)
{
    int rc = -1;
    if (fd != -1 && close(fd) == 0) {
        fd = -1;
        rc = 0;
    }
    return rc;
}

#endif

#endif