diff options
Diffstat (limited to 'sc25519.c')
-rw-r--r-- | sc25519.c | 308 |
1 files changed, 308 insertions, 0 deletions
diff --git a/sc25519.c b/sc25519.c new file mode 100644 index 0000000..1568d9a --- /dev/null +++ b/sc25519.c @@ -0,0 +1,308 @@ +/* $OpenBSD: sc25519.c,v 1.3 2013/12/09 11:03:45 markus Exp $ */ + +/* + * Public Domain, Authors: Daniel J. Bernstein, Niels Duif, Tanja Lange, + * Peter Schwabe, Bo-Yin Yang. + * Copied from supercop-20130419/crypto_sign/ed25519/ref/sc25519.c + */ + +#include "includes.h" + +#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); +} |