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openssh/sc25519.c
Damien Miller 5be9d9e3cb - markus@cvs.openbsd.org 2013/12/06 13:39:49 
[authfd.c authfile.c key.c key.h myproposal.h pathnames.h readconf.c]
     [servconf.c ssh-agent.c ssh-keygen.c ssh-keyscan.1 ssh-keyscan.c]
     [ssh-keysign.c ssh.c ssh_config.5 sshd.8 sshd.c verify.c ssh-ed25519.c]
     [sc25519.h sc25519.c hash.c ge25519_base.data ge25519.h ge25519.c]
     [fe25519.h fe25519.c ed25519.c crypto_api.h blocks.c]
     support ed25519 keys (hostkeys and user identities) using the public
     domain ed25519 reference code from SUPERCOP, see
     http://ed25519.cr.yp.to/software.html
     feedback, help & ok djm@
2013-12-07 11:24:01 +11:00

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/* $OpenBSD: */
/* Public Domain, from supercop-20130419/crypto_sign/ed25519/ref/sc25519.c */
#include "sc25519.h"
/*Arithmetic modulo the group order m = 2^252 + 27742317777372353535851937790883648493 = 7237005577332262213973186563042994240857116359379907606001950938285454250989 */
static const crypto_uint32 m[32] = {0xED, 0xD3, 0xF5, 0x5C, 0x1A, 0x63, 0x12, 0x58, 0xD6, 0x9C, 0xF7, 0xA2, 0xDE, 0xF9, 0xDE, 0x14,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x10};
static const crypto_uint32 mu[33] = {0x1B, 0x13, 0x2C, 0x0A, 0xA3, 0xE5, 0x9C, 0xED, 0xA7, 0x29, 0x63, 0x08, 0x5D, 0x21, 0x06, 0x21,
0xEB, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x0F};
static crypto_uint32 lt(crypto_uint32 a,crypto_uint32 b) /* 16-bit inputs */
{
unsigned int x = a;
x -= (unsigned int) b; /* 0..65535: no; 4294901761..4294967295: yes */
x >>= 31; /* 0: no; 1: yes */
return x;
}
/* Reduce coefficients of r before calling reduce_add_sub */
static void reduce_add_sub(sc25519 *r)
{
crypto_uint32 pb = 0;
crypto_uint32 b;
crypto_uint32 mask;
int i;
unsigned char t[32];
for(i=0;i<32;i++)
{
pb += m[i];
b = lt(r->v[i],pb);
t[i] = r->v[i]-pb+(b<<8);
pb = b;
}
mask = b - 1;
for(i=0;i<32;i++)
r->v[i] ^= mask & (r->v[i] ^ t[i]);
}
/* Reduce coefficients of x before calling barrett_reduce */
static void barrett_reduce(sc25519 *r, const crypto_uint32 x[64])
{
/* See HAC, Alg. 14.42 */
int i,j;
crypto_uint32 q2[66];
crypto_uint32 *q3 = q2 + 33;
crypto_uint32 r1[33];
crypto_uint32 r2[33];
crypto_uint32 carry;
crypto_uint32 pb = 0;
crypto_uint32 b;
for (i = 0;i < 66;++i) q2[i] = 0;
for (i = 0;i < 33;++i) r2[i] = 0;
for(i=0;i<33;i++)
for(j=0;j<33;j++)
if(i+j >= 31) q2[i+j] += mu[i]*x[j+31];
carry = q2[31] >> 8;
q2[32] += carry;
carry = q2[32] >> 8;
q2[33] += carry;
for(i=0;i<33;i++)r1[i] = x[i];
for(i=0;i<32;i++)
for(j=0;j<33;j++)
if(i+j < 33) r2[i+j] += m[i]*q3[j];
for(i=0;i<32;i++)
{
carry = r2[i] >> 8;
r2[i+1] += carry;
r2[i] &= 0xff;
}
for(i=0;i<32;i++)
{
pb += r2[i];
b = lt(r1[i],pb);
r->v[i] = r1[i]-pb+(b<<8);
pb = b;
}
/* XXX: Can it really happen that r<0?, See HAC, Alg 14.42, Step 3
* If so: Handle it here!
*/
reduce_add_sub(r);
reduce_add_sub(r);
}
void sc25519_from32bytes(sc25519 *r, const unsigned char x[32])
{
int i;
crypto_uint32 t[64];
for(i=0;i<32;i++) t[i] = x[i];
for(i=32;i<64;++i) t[i] = 0;
barrett_reduce(r, t);
}
void shortsc25519_from16bytes(shortsc25519 *r, const unsigned char x[16])
{
int i;
for(i=0;i<16;i++) r->v[i] = x[i];
}
void sc25519_from64bytes(sc25519 *r, const unsigned char x[64])
{
int i;
crypto_uint32 t[64];
for(i=0;i<64;i++) t[i] = x[i];
barrett_reduce(r, t);
}
void sc25519_from_shortsc(sc25519 *r, const shortsc25519 *x)
{
int i;
for(i=0;i<16;i++)
r->v[i] = x->v[i];
for(i=0;i<16;i++)
r->v[16+i] = 0;
}
void sc25519_to32bytes(unsigned char r[32], const sc25519 *x)
{
int i;
for(i=0;i<32;i++) r[i] = x->v[i];
}
int sc25519_iszero_vartime(const sc25519 *x)
{
int i;
for(i=0;i<32;i++)
if(x->v[i] != 0) return 0;
return 1;
}
int sc25519_isshort_vartime(const sc25519 *x)
{
int i;
for(i=31;i>15;i--)
if(x->v[i] != 0) return 0;
return 1;
}
int sc25519_lt_vartime(const sc25519 *x, const sc25519 *y)
{
int i;
for(i=31;i>=0;i--)
{
if(x->v[i] < y->v[i]) return 1;
if(x->v[i] > y->v[i]) return 0;
}
return 0;
}
void sc25519_add(sc25519 *r, const sc25519 *x, const sc25519 *y)
{
int i, carry;
for(i=0;i<32;i++) r->v[i] = x->v[i] + y->v[i];
for(i=0;i<31;i++)
{
carry = r->v[i] >> 8;
r->v[i+1] += carry;
r->v[i] &= 0xff;
}
reduce_add_sub(r);
}
void sc25519_sub_nored(sc25519 *r, const sc25519 *x, const sc25519 *y)
{
crypto_uint32 b = 0;
crypto_uint32 t;
int i;
for(i=0;i<32;i++)
{
t = x->v[i] - y->v[i] - b;
r->v[i] = t & 255;
b = (t >> 8) & 1;
}
}
void sc25519_mul(sc25519 *r, const sc25519 *x, const sc25519 *y)
{
int i,j,carry;
crypto_uint32 t[64];
for(i=0;i<64;i++)t[i] = 0;
for(i=0;i<32;i++)
for(j=0;j<32;j++)
t[i+j] += x->v[i] * y->v[j];
/* Reduce coefficients */
for(i=0;i<63;i++)
{
carry = t[i] >> 8;
t[i+1] += carry;
t[i] &= 0xff;
}
barrett_reduce(r, t);
}
void sc25519_mul_shortsc(sc25519 *r, const sc25519 *x, const shortsc25519 *y)
{
sc25519 t;
sc25519_from_shortsc(&t, y);
sc25519_mul(r, x, &t);
}
void sc25519_window3(signed char r[85], const sc25519 *s)
{
char carry;
int i;
for(i=0;i<10;i++)
{
r[8*i+0] = s->v[3*i+0] & 7;
r[8*i+1] = (s->v[3*i+0] >> 3) & 7;
r[8*i+2] = (s->v[3*i+0] >> 6) & 7;
r[8*i+2] ^= (s->v[3*i+1] << 2) & 7;
r[8*i+3] = (s->v[3*i+1] >> 1) & 7;
r[8*i+4] = (s->v[3*i+1] >> 4) & 7;
r[8*i+5] = (s->v[3*i+1] >> 7) & 7;
r[8*i+5] ^= (s->v[3*i+2] << 1) & 7;
r[8*i+6] = (s->v[3*i+2] >> 2) & 7;
r[8*i+7] = (s->v[3*i+2] >> 5) & 7;
}
r[8*i+0] = s->v[3*i+0] & 7;
r[8*i+1] = (s->v[3*i+0] >> 3) & 7;
r[8*i+2] = (s->v[3*i+0] >> 6) & 7;
r[8*i+2] ^= (s->v[3*i+1] << 2) & 7;
r[8*i+3] = (s->v[3*i+1] >> 1) & 7;
r[8*i+4] = (s->v[3*i+1] >> 4) & 7;
/* Making it signed */
carry = 0;
for(i=0;i<84;i++)
{
r[i] += carry;
r[i+1] += r[i] >> 3;
r[i] &= 7;
carry = r[i] >> 2;
r[i] -= carry<<3;
}
r[84] += carry;
}
void sc25519_window5(signed char r[51], const sc25519 *s)
{
char carry;
int i;
for(i=0;i<6;i++)
{
r[8*i+0] = s->v[5*i+0] & 31;
r[8*i+1] = (s->v[5*i+0] >> 5) & 31;
r[8*i+1] ^= (s->v[5*i+1] << 3) & 31;
r[8*i+2] = (s->v[5*i+1] >> 2) & 31;
r[8*i+3] = (s->v[5*i+1] >> 7) & 31;
r[8*i+3] ^= (s->v[5*i+2] << 1) & 31;
r[8*i+4] = (s->v[5*i+2] >> 4) & 31;
r[8*i+4] ^= (s->v[5*i+3] << 4) & 31;
r[8*i+5] = (s->v[5*i+3] >> 1) & 31;
r[8*i+6] = (s->v[5*i+3] >> 6) & 31;
r[8*i+6] ^= (s->v[5*i+4] << 2) & 31;
r[8*i+7] = (s->v[5*i+4] >> 3) & 31;
}
r[8*i+0] = s->v[5*i+0] & 31;
r[8*i+1] = (s->v[5*i+0] >> 5) & 31;
r[8*i+1] ^= (s->v[5*i+1] << 3) & 31;
r[8*i+2] = (s->v[5*i+1] >> 2) & 31;
/* Making it signed */
carry = 0;
for(i=0;i<50;i++)
{
r[i] += carry;
r[i+1] += r[i] >> 5;
r[i] &= 31;
carry = r[i] >> 4;
r[i] -= carry<<5;
}
r[50] += carry;
}
void sc25519_2interleave2(unsigned char r[127], const sc25519 *s1, const sc25519 *s2)
{
int i;
for(i=0;i<31;i++)
{
r[4*i] = ( s1->v[i] & 3) ^ (( s2->v[i] & 3) << 2);
r[4*i+1] = ((s1->v[i] >> 2) & 3) ^ (((s2->v[i] >> 2) & 3) << 2);
r[4*i+2] = ((s1->v[i] >> 4) & 3) ^ (((s2->v[i] >> 4) & 3) << 2);
r[4*i+3] = ((s1->v[i] >> 6) & 3) ^ (((s2->v[i] >> 6) & 3) << 2);
}
r[124] = ( s1->v[31] & 3) ^ (( s2->v[31] & 3) << 2);
r[125] = ((s1->v[31] >> 2) & 3) ^ (((s2->v[31] >> 2) & 3) << 2);
r[126] = ((s1->v[31] >> 4) & 3) ^ (((s2->v[31] >> 4) & 3) << 2);
}
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