Annotation of src/usr.bin/signify/ge25519.c, Revision 1.1
1.1 ! deraadt 1: /* $OpenBSD: ge25519.c,v 1.3 2013/12/09 11:03:45 markus Exp $ */
! 2:
! 3: /*
! 4: * Public Domain, Authors: Daniel J. Bernstein, Niels Duif, Tanja Lange,
! 5: * Peter Schwabe, Bo-Yin Yang.
! 6: * Copied from supercop-20130419/crypto_sign/ed25519/ref/ge25519.c
! 7: */
! 8:
! 9: #include "fe25519.h"
! 10: #include "sc25519.h"
! 11: #include "ge25519.h"
! 12:
! 13: /*
! 14: * Arithmetic on the twisted Edwards curve -x^2 + y^2 = 1 + dx^2y^2
! 15: * with d = -(121665/121666) = 37095705934669439343138083508754565189542113879843219016388785533085940283555
! 16: * Base point: (15112221349535400772501151409588531511454012693041857206046113283949847762202,46316835694926478169428394003475163141307993866256225615783033603165251855960);
! 17: */
! 18:
! 19: /* d */
! 20: static const fe25519 ge25519_ecd = {{0xA3, 0x78, 0x59, 0x13, 0xCA, 0x4D, 0xEB, 0x75, 0xAB, 0xD8, 0x41, 0x41, 0x4D, 0x0A, 0x70, 0x00,
! 21: 0x98, 0xE8, 0x79, 0x77, 0x79, 0x40, 0xC7, 0x8C, 0x73, 0xFE, 0x6F, 0x2B, 0xEE, 0x6C, 0x03, 0x52}};
! 22: /* 2*d */
! 23: static const fe25519 ge25519_ec2d = {{0x59, 0xF1, 0xB2, 0x26, 0x94, 0x9B, 0xD6, 0xEB, 0x56, 0xB1, 0x83, 0x82, 0x9A, 0x14, 0xE0, 0x00,
! 24: 0x30, 0xD1, 0xF3, 0xEE, 0xF2, 0x80, 0x8E, 0x19, 0xE7, 0xFC, 0xDF, 0x56, 0xDC, 0xD9, 0x06, 0x24}};
! 25: /* sqrt(-1) */
! 26: static const fe25519 ge25519_sqrtm1 = {{0xB0, 0xA0, 0x0E, 0x4A, 0x27, 0x1B, 0xEE, 0xC4, 0x78, 0xE4, 0x2F, 0xAD, 0x06, 0x18, 0x43, 0x2F,
! 27: 0xA7, 0xD7, 0xFB, 0x3D, 0x99, 0x00, 0x4D, 0x2B, 0x0B, 0xDF, 0xC1, 0x4F, 0x80, 0x24, 0x83, 0x2B}};
! 28:
! 29: #define ge25519_p3 ge25519
! 30:
! 31: typedef struct
! 32: {
! 33: fe25519 x;
! 34: fe25519 z;
! 35: fe25519 y;
! 36: fe25519 t;
! 37: } ge25519_p1p1;
! 38:
! 39: typedef struct
! 40: {
! 41: fe25519 x;
! 42: fe25519 y;
! 43: fe25519 z;
! 44: } ge25519_p2;
! 45:
! 46: typedef struct
! 47: {
! 48: fe25519 x;
! 49: fe25519 y;
! 50: } ge25519_aff;
! 51:
! 52:
! 53: /* Packed coordinates of the base point */
! 54: const ge25519 ge25519_base = {{{0x1A, 0xD5, 0x25, 0x8F, 0x60, 0x2D, 0x56, 0xC9, 0xB2, 0xA7, 0x25, 0x95, 0x60, 0xC7, 0x2C, 0x69,
! 55: 0x5C, 0xDC, 0xD6, 0xFD, 0x31, 0xE2, 0xA4, 0xC0, 0xFE, 0x53, 0x6E, 0xCD, 0xD3, 0x36, 0x69, 0x21}},
! 56: {{0x58, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66,
! 57: 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66, 0x66}},
! 58: {{0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
! 59: 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}},
! 60: {{0xA3, 0xDD, 0xB7, 0xA5, 0xB3, 0x8A, 0xDE, 0x6D, 0xF5, 0x52, 0x51, 0x77, 0x80, 0x9F, 0xF0, 0x20,
! 61: 0x7D, 0xE3, 0xAB, 0x64, 0x8E, 0x4E, 0xEA, 0x66, 0x65, 0x76, 0x8B, 0xD7, 0x0F, 0x5F, 0x87, 0x67}}};
! 62:
! 63: /* Multiples of the base point in affine representation */
! 64: static const ge25519_aff ge25519_base_multiples_affine[425] = {
! 65: #include "ge25519_base.data"
! 66: };
! 67:
! 68: static void p1p1_to_p2(ge25519_p2 *r, const ge25519_p1p1 *p)
! 69: {
! 70: fe25519_mul(&r->x, &p->x, &p->t);
! 71: fe25519_mul(&r->y, &p->y, &p->z);
! 72: fe25519_mul(&r->z, &p->z, &p->t);
! 73: }
! 74:
! 75: static void p1p1_to_p3(ge25519_p3 *r, const ge25519_p1p1 *p)
! 76: {
! 77: p1p1_to_p2((ge25519_p2 *)r, p);
! 78: fe25519_mul(&r->t, &p->x, &p->y);
! 79: }
! 80:
! 81: static void ge25519_mixadd2(ge25519_p3 *r, const ge25519_aff *q)
! 82: {
! 83: fe25519 a,b,t1,t2,c,d,e,f,g,h,qt;
! 84: fe25519_mul(&qt, &q->x, &q->y);
! 85: fe25519_sub(&a, &r->y, &r->x); /* A = (Y1-X1)*(Y2-X2) */
! 86: fe25519_add(&b, &r->y, &r->x); /* B = (Y1+X1)*(Y2+X2) */
! 87: fe25519_sub(&t1, &q->y, &q->x);
! 88: fe25519_add(&t2, &q->y, &q->x);
! 89: fe25519_mul(&a, &a, &t1);
! 90: fe25519_mul(&b, &b, &t2);
! 91: fe25519_sub(&e, &b, &a); /* E = B-A */
! 92: fe25519_add(&h, &b, &a); /* H = B+A */
! 93: fe25519_mul(&c, &r->t, &qt); /* C = T1*k*T2 */
! 94: fe25519_mul(&c, &c, &ge25519_ec2d);
! 95: fe25519_add(&d, &r->z, &r->z); /* D = Z1*2 */
! 96: fe25519_sub(&f, &d, &c); /* F = D-C */
! 97: fe25519_add(&g, &d, &c); /* G = D+C */
! 98: fe25519_mul(&r->x, &e, &f);
! 99: fe25519_mul(&r->y, &h, &g);
! 100: fe25519_mul(&r->z, &g, &f);
! 101: fe25519_mul(&r->t, &e, &h);
! 102: }
! 103:
! 104: static void add_p1p1(ge25519_p1p1 *r, const ge25519_p3 *p, const ge25519_p3 *q)
! 105: {
! 106: fe25519 a, b, c, d, t;
! 107:
! 108: fe25519_sub(&a, &p->y, &p->x); /* A = (Y1-X1)*(Y2-X2) */
! 109: fe25519_sub(&t, &q->y, &q->x);
! 110: fe25519_mul(&a, &a, &t);
! 111: fe25519_add(&b, &p->x, &p->y); /* B = (Y1+X1)*(Y2+X2) */
! 112: fe25519_add(&t, &q->x, &q->y);
! 113: fe25519_mul(&b, &b, &t);
! 114: fe25519_mul(&c, &p->t, &q->t); /* C = T1*k*T2 */
! 115: fe25519_mul(&c, &c, &ge25519_ec2d);
! 116: fe25519_mul(&d, &p->z, &q->z); /* D = Z1*2*Z2 */
! 117: fe25519_add(&d, &d, &d);
! 118: fe25519_sub(&r->x, &b, &a); /* E = B-A */
! 119: fe25519_sub(&r->t, &d, &c); /* F = D-C */
! 120: fe25519_add(&r->z, &d, &c); /* G = D+C */
! 121: fe25519_add(&r->y, &b, &a); /* H = B+A */
! 122: }
! 123:
! 124: /* See http://www.hyperelliptic.org/EFD/g1p/auto-twisted-extended-1.html#doubling-dbl-2008-hwcd */
! 125: static void dbl_p1p1(ge25519_p1p1 *r, const ge25519_p2 *p)
! 126: {
! 127: fe25519 a,b,c,d;
! 128: fe25519_square(&a, &p->x);
! 129: fe25519_square(&b, &p->y);
! 130: fe25519_square(&c, &p->z);
! 131: fe25519_add(&c, &c, &c);
! 132: fe25519_neg(&d, &a);
! 133:
! 134: fe25519_add(&r->x, &p->x, &p->y);
! 135: fe25519_square(&r->x, &r->x);
! 136: fe25519_sub(&r->x, &r->x, &a);
! 137: fe25519_sub(&r->x, &r->x, &b);
! 138: fe25519_add(&r->z, &d, &b);
! 139: fe25519_sub(&r->t, &r->z, &c);
! 140: fe25519_sub(&r->y, &d, &b);
! 141: }
! 142:
! 143: /* Constant-time version of: if(b) r = p */
! 144: static void cmov_aff(ge25519_aff *r, const ge25519_aff *p, unsigned char b)
! 145: {
! 146: fe25519_cmov(&r->x, &p->x, b);
! 147: fe25519_cmov(&r->y, &p->y, b);
! 148: }
! 149:
! 150: static unsigned char equal(signed char b,signed char c)
! 151: {
! 152: unsigned char ub = b;
! 153: unsigned char uc = c;
! 154: unsigned char x = ub ^ uc; /* 0: yes; 1..255: no */
! 155: crypto_uint32 y = x; /* 0: yes; 1..255: no */
! 156: y -= 1; /* 4294967295: yes; 0..254: no */
! 157: y >>= 31; /* 1: yes; 0: no */
! 158: return y;
! 159: }
! 160:
! 161: static unsigned char negative(signed char b)
! 162: {
! 163: unsigned long long x = b; /* 18446744073709551361..18446744073709551615: yes; 0..255: no */
! 164: x >>= 63; /* 1: yes; 0: no */
! 165: return x;
! 166: }
! 167:
! 168: static void choose_t(ge25519_aff *t, unsigned long long pos, signed char b)
! 169: {
! 170: /* constant time */
! 171: fe25519 v;
! 172: *t = ge25519_base_multiples_affine[5*pos+0];
! 173: cmov_aff(t, &ge25519_base_multiples_affine[5*pos+1],equal(b,1) | equal(b,-1));
! 174: cmov_aff(t, &ge25519_base_multiples_affine[5*pos+2],equal(b,2) | equal(b,-2));
! 175: cmov_aff(t, &ge25519_base_multiples_affine[5*pos+3],equal(b,3) | equal(b,-3));
! 176: cmov_aff(t, &ge25519_base_multiples_affine[5*pos+4],equal(b,-4));
! 177: fe25519_neg(&v, &t->x);
! 178: fe25519_cmov(&t->x, &v, negative(b));
! 179: }
! 180:
! 181: static void setneutral(ge25519 *r)
! 182: {
! 183: fe25519_setzero(&r->x);
! 184: fe25519_setone(&r->y);
! 185: fe25519_setone(&r->z);
! 186: fe25519_setzero(&r->t);
! 187: }
! 188:
! 189: /* ********************************************************************
! 190: * EXPORTED FUNCTIONS
! 191: ******************************************************************** */
! 192:
! 193: /* return 0 on success, -1 otherwise */
! 194: int ge25519_unpackneg_vartime(ge25519_p3 *r, const unsigned char p[32])
! 195: {
! 196: unsigned char par;
! 197: fe25519 t, chk, num, den, den2, den4, den6;
! 198: fe25519_setone(&r->z);
! 199: par = p[31] >> 7;
! 200: fe25519_unpack(&r->y, p);
! 201: fe25519_square(&num, &r->y); /* x = y^2 */
! 202: fe25519_mul(&den, &num, &ge25519_ecd); /* den = dy^2 */
! 203: fe25519_sub(&num, &num, &r->z); /* x = y^2-1 */
! 204: fe25519_add(&den, &r->z, &den); /* den = dy^2+1 */
! 205:
! 206: /* Computation of sqrt(num/den) */
! 207: /* 1.: computation of num^((p-5)/8)*den^((7p-35)/8) = (num*den^7)^((p-5)/8) */
! 208: fe25519_square(&den2, &den);
! 209: fe25519_square(&den4, &den2);
! 210: fe25519_mul(&den6, &den4, &den2);
! 211: fe25519_mul(&t, &den6, &num);
! 212: fe25519_mul(&t, &t, &den);
! 213:
! 214: fe25519_pow2523(&t, &t);
! 215: /* 2. computation of r->x = t * num * den^3 */
! 216: fe25519_mul(&t, &t, &num);
! 217: fe25519_mul(&t, &t, &den);
! 218: fe25519_mul(&t, &t, &den);
! 219: fe25519_mul(&r->x, &t, &den);
! 220:
! 221: /* 3. Check whether sqrt computation gave correct result, multiply by sqrt(-1) if not: */
! 222: fe25519_square(&chk, &r->x);
! 223: fe25519_mul(&chk, &chk, &den);
! 224: if (!fe25519_iseq_vartime(&chk, &num))
! 225: fe25519_mul(&r->x, &r->x, &ge25519_sqrtm1);
! 226:
! 227: /* 4. Now we have one of the two square roots, except if input was not a square */
! 228: fe25519_square(&chk, &r->x);
! 229: fe25519_mul(&chk, &chk, &den);
! 230: if (!fe25519_iseq_vartime(&chk, &num))
! 231: return -1;
! 232:
! 233: /* 5. Choose the desired square root according to parity: */
! 234: if(fe25519_getparity(&r->x) != (1-par))
! 235: fe25519_neg(&r->x, &r->x);
! 236:
! 237: fe25519_mul(&r->t, &r->x, &r->y);
! 238: return 0;
! 239: }
! 240:
! 241: void ge25519_pack(unsigned char r[32], const ge25519_p3 *p)
! 242: {
! 243: fe25519 tx, ty, zi;
! 244: fe25519_invert(&zi, &p->z);
! 245: fe25519_mul(&tx, &p->x, &zi);
! 246: fe25519_mul(&ty, &p->y, &zi);
! 247: fe25519_pack(r, &ty);
! 248: r[31] ^= fe25519_getparity(&tx) << 7;
! 249: }
! 250:
! 251: int ge25519_isneutral_vartime(const ge25519_p3 *p)
! 252: {
! 253: int ret = 1;
! 254: if(!fe25519_iszero(&p->x)) ret = 0;
! 255: if(!fe25519_iseq_vartime(&p->y, &p->z)) ret = 0;
! 256: return ret;
! 257: }
! 258:
! 259: /* computes [s1]p1 + [s2]p2 */
! 260: void ge25519_double_scalarmult_vartime(ge25519_p3 *r, const ge25519_p3 *p1, const sc25519 *s1, const ge25519_p3 *p2, const sc25519 *s2)
! 261: {
! 262: ge25519_p1p1 tp1p1;
! 263: ge25519_p3 pre[16];
! 264: unsigned char b[127];
! 265: int i;
! 266:
! 267: /* precomputation s2 s1 */
! 268: setneutral(pre); /* 00 00 */
! 269: pre[1] = *p1; /* 00 01 */
! 270: dbl_p1p1(&tp1p1,(ge25519_p2 *)p1); p1p1_to_p3( &pre[2], &tp1p1); /* 00 10 */
! 271: add_p1p1(&tp1p1,&pre[1], &pre[2]); p1p1_to_p3( &pre[3], &tp1p1); /* 00 11 */
! 272: pre[4] = *p2; /* 01 00 */
! 273: add_p1p1(&tp1p1,&pre[1], &pre[4]); p1p1_to_p3( &pre[5], &tp1p1); /* 01 01 */
! 274: add_p1p1(&tp1p1,&pre[2], &pre[4]); p1p1_to_p3( &pre[6], &tp1p1); /* 01 10 */
! 275: add_p1p1(&tp1p1,&pre[3], &pre[4]); p1p1_to_p3( &pre[7], &tp1p1); /* 01 11 */
! 276: dbl_p1p1(&tp1p1,(ge25519_p2 *)p2); p1p1_to_p3( &pre[8], &tp1p1); /* 10 00 */
! 277: add_p1p1(&tp1p1,&pre[1], &pre[8]); p1p1_to_p3( &pre[9], &tp1p1); /* 10 01 */
! 278: dbl_p1p1(&tp1p1,(ge25519_p2 *)&pre[5]); p1p1_to_p3(&pre[10], &tp1p1); /* 10 10 */
! 279: add_p1p1(&tp1p1,&pre[3], &pre[8]); p1p1_to_p3(&pre[11], &tp1p1); /* 10 11 */
! 280: add_p1p1(&tp1p1,&pre[4], &pre[8]); p1p1_to_p3(&pre[12], &tp1p1); /* 11 00 */
! 281: add_p1p1(&tp1p1,&pre[1],&pre[12]); p1p1_to_p3(&pre[13], &tp1p1); /* 11 01 */
! 282: add_p1p1(&tp1p1,&pre[2],&pre[12]); p1p1_to_p3(&pre[14], &tp1p1); /* 11 10 */
! 283: add_p1p1(&tp1p1,&pre[3],&pre[12]); p1p1_to_p3(&pre[15], &tp1p1); /* 11 11 */
! 284:
! 285: sc25519_2interleave2(b,s1,s2);
! 286:
! 287: /* scalar multiplication */
! 288: *r = pre[b[126]];
! 289: for(i=125;i>=0;i--)
! 290: {
! 291: dbl_p1p1(&tp1p1, (ge25519_p2 *)r);
! 292: p1p1_to_p2((ge25519_p2 *) r, &tp1p1);
! 293: dbl_p1p1(&tp1p1, (ge25519_p2 *)r);
! 294: if(b[i]!=0)
! 295: {
! 296: p1p1_to_p3(r, &tp1p1);
! 297: add_p1p1(&tp1p1, r, &pre[b[i]]);
! 298: }
! 299: if(i != 0) p1p1_to_p2((ge25519_p2 *)r, &tp1p1);
! 300: else p1p1_to_p3(r, &tp1p1);
! 301: }
! 302: }
! 303:
! 304: void ge25519_scalarmult_base(ge25519_p3 *r, const sc25519 *s)
! 305: {
! 306: signed char b[85];
! 307: int i;
! 308: ge25519_aff t;
! 309: sc25519_window3(b,s);
! 310:
! 311: choose_t((ge25519_aff *)r, 0, b[0]);
! 312: fe25519_setone(&r->z);
! 313: fe25519_mul(&r->t, &r->x, &r->y);
! 314: for(i=1;i<85;i++)
! 315: {
! 316: choose_t(&t, (unsigned long long) i, b[i]);
! 317: ge25519_mixadd2(r, &t);
! 318: }
! 319: }