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add chacha20 function
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@apoelstra @jonasnick
apoelstra authored and jonasnick committed Nov 1, 2018
1 parent 123db29 commit 7bca01d
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3 changes: 3 additions & 0 deletions src/scalar.h
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Original file line number Diff line number Diff line change
Expand Up @@ -103,4 +103,7 @@ static void secp256k1_scalar_split_lambda(secp256k1_scalar *r1, secp256k1_scalar
/** Multiply a and b (without taking the modulus!), divide by 2**shift, and round to the nearest integer. Shift must be at least 256. */
static void secp256k1_scalar_mul_shift_var(secp256k1_scalar *r, const secp256k1_scalar *a, const secp256k1_scalar *b, unsigned int shift);

/** Generate two scalars from a 32-byte seed and an integer using the chacha20 stream cipher */
static void secp256k1_scalar_chacha20(secp256k1_scalar *r1, secp256k1_scalar *r2, const unsigned char *seed, uint64_t idx);

#endif /* SECP256K1_SCALAR_H */
93 changes: 93 additions & 0 deletions src/scalar_4x64_impl.h
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Expand Up @@ -7,6 +7,9 @@
#ifndef SECP256K1_SCALAR_REPR_IMPL_H
#define SECP256K1_SCALAR_REPR_IMPL_H

#include "scalar.h"
#include <string.h>

/* Limbs of the secp256k1 order. */
#define SECP256K1_N_0 ((uint64_t)0xBFD25E8CD0364141ULL)
#define SECP256K1_N_1 ((uint64_t)0xBAAEDCE6AF48A03BULL)
Expand Down Expand Up @@ -946,4 +949,94 @@ SECP256K1_INLINE static void secp256k1_scalar_mul_shift_var(secp256k1_scalar *r,
secp256k1_scalar_cadd_bit(r, 0, (l[(shift - 1) >> 6] >> ((shift - 1) & 0x3f)) & 1);
}

#define ROTL32(x,n) ((x) << (n) | (x) >> (32-(n)))
#define QUARTERROUND(a,b,c,d) \
a += b; d = ROTL32(d ^ a, 16); \
c += d; b = ROTL32(b ^ c, 12); \
a += b; d = ROTL32(d ^ a, 8); \
c += d; b = ROTL32(b ^ c, 7);

#ifdef WORDS_BIGENDIAN
#define LE32(p) ((((p) & 0xFF) << 24) | (((p) & 0xFF00) << 8) | (((p) & 0xFF0000) >> 8) | (((p) & 0xFF000000) >> 24))
#define BE32(p) (p)
#else
#define BE32(p) ((((p) & 0xFF) << 24) | (((p) & 0xFF00) << 8) | (((p) & 0xFF0000) >> 8) | (((p) & 0xFF000000) >> 24))
#define LE32(p) (p)
#endif

static void secp256k1_scalar_chacha20(secp256k1_scalar *r1, secp256k1_scalar *r2, const unsigned char *seed, uint64_t idx) {
size_t n;
size_t over_count = 0;
uint32_t seed32[8];
uint32_t x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;
int over1, over2;

memcpy((void *) seed32, (const void *) seed, 32);
do {
x0 = 0x61707865;
x1 = 0x3320646e;
x2 = 0x79622d32;
x3 = 0x6b206574;
x4 = LE32(seed32[0]);
x5 = LE32(seed32[1]);
x6 = LE32(seed32[2]);
x7 = LE32(seed32[3]);
x8 = LE32(seed32[4]);
x9 = LE32(seed32[5]);
x10 = LE32(seed32[6]);
x11 = LE32(seed32[7]);
x12 = idx;
x13 = idx >> 32;
x14 = 0;
x15 = over_count;

n = 10;
while (n--) {
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 += 0x61707865;
x1 += 0x3320646e;
x2 += 0x79622d32;
x3 += 0x6b206574;
x4 += LE32(seed32[0]);
x5 += LE32(seed32[1]);
x6 += LE32(seed32[2]);
x7 += LE32(seed32[3]);
x8 += LE32(seed32[4]);
x9 += LE32(seed32[5]);
x10 += LE32(seed32[6]);
x11 += LE32(seed32[7]);
x12 += idx;
x13 += idx >> 32;
x14 += 0;
x15 += over_count;

r1->d[3] = BE32((uint64_t) x0) << 32 | BE32(x1);
r1->d[2] = BE32((uint64_t) x2) << 32 | BE32(x3);
r1->d[1] = BE32((uint64_t) x4) << 32 | BE32(x5);
r1->d[0] = BE32((uint64_t) x6) << 32 | BE32(x7);
r2->d[3] = BE32((uint64_t) x8) << 32 | BE32(x9);
r2->d[2] = BE32((uint64_t) x10) << 32 | BE32(x11);
r2->d[1] = BE32((uint64_t) x12) << 32 | BE32(x13);
r2->d[0] = BE32((uint64_t) x14) << 32 | BE32(x15);

over1 = secp256k1_scalar_check_overflow(r1);
over2 = secp256k1_scalar_check_overflow(r2);
over_count++;
} while (over1 | over2);
}

#undef ROTL32
#undef QUARTERROUND
#undef BE32
#undef LE32

#endif /* SECP256K1_SCALAR_REPR_IMPL_H */
100 changes: 100 additions & 0 deletions src/scalar_8x32_impl.h
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Expand Up @@ -7,6 +7,8 @@
#ifndef SECP256K1_SCALAR_REPR_IMPL_H
#define SECP256K1_SCALAR_REPR_IMPL_H

#include <string.h>

/* Limbs of the secp256k1 order. */
#define SECP256K1_N_0 ((uint32_t)0xD0364141UL)
#define SECP256K1_N_1 ((uint32_t)0xBFD25E8CUL)
Expand Down Expand Up @@ -718,4 +720,102 @@ SECP256K1_INLINE static void secp256k1_scalar_mul_shift_var(secp256k1_scalar *r,
secp256k1_scalar_cadd_bit(r, 0, (l[(shift - 1) >> 5] >> ((shift - 1) & 0x1f)) & 1);
}

#define ROTL32(x,n) ((x) << (n) | (x) >> (32-(n)))
#define QUARTERROUND(a,b,c,d) \
a += b; d = ROTL32(d ^ a, 16); \
c += d; b = ROTL32(b ^ c, 12); \
a += b; d = ROTL32(d ^ a, 8); \
c += d; b = ROTL32(b ^ c, 7);

#ifdef WORDS_BIGENDIAN
#define LE32(p) ((((p) & 0xFF) << 24) | (((p) & 0xFF00) << 8) | (((p) & 0xFF0000) >> 8) | (((p) & 0xFF000000) >> 24))
#define BE32(p) (p)
#else
#define BE32(p) ((((p) & 0xFF) << 24) | (((p) & 0xFF00) << 8) | (((p) & 0xFF0000) >> 8) | (((p) & 0xFF000000) >> 24))
#define LE32(p) (p)
#endif

static void secp256k1_scalar_chacha20(secp256k1_scalar *r1, secp256k1_scalar *r2, const unsigned char *seed, uint64_t idx) {
size_t n;
size_t over_count = 0;
uint32_t seed32[8];
uint32_t x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;
int over1, over2;

memcpy((void *) seed32, (const void *) seed, 32);
do {
x0 = 0x61707865;
x1 = 0x3320646e;
x2 = 0x79622d32;
x3 = 0x6b206574;
x4 = LE32(seed32[0]);
x5 = LE32(seed32[1]);
x6 = LE32(seed32[2]);
x7 = LE32(seed32[3]);
x8 = LE32(seed32[4]);
x9 = LE32(seed32[5]);
x10 = LE32(seed32[6]);
x11 = LE32(seed32[7]);
x12 = idx;
x13 = idx >> 32;
x14 = 0;
x15 = over_count;

n = 10;
while (n--) {
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 += 0x61707865;
x1 += 0x3320646e;
x2 += 0x79622d32;
x3 += 0x6b206574;
x4 += LE32(seed32[0]);
x5 += LE32(seed32[1]);
x6 += LE32(seed32[2]);
x7 += LE32(seed32[3]);
x8 += LE32(seed32[4]);
x9 += LE32(seed32[5]);
x10 += LE32(seed32[6]);
x11 += LE32(seed32[7]);
x12 += idx;
x13 += idx >> 32;
x14 += 0;
x15 += over_count;

r1->d[7] = BE32(x0);
r1->d[6] = BE32(x1);
r1->d[5] = BE32(x2);
r1->d[4] = BE32(x3);
r1->d[3] = BE32(x4);
r1->d[2] = BE32(x5);
r1->d[1] = BE32(x6);
r1->d[0] = BE32(x7);
r2->d[7] = BE32(x8);
r2->d[6] = BE32(x9);
r2->d[5] = BE32(x10);
r2->d[4] = BE32(x11);
r2->d[3] = BE32(x12);
r2->d[2] = BE32(x13);
r2->d[1] = BE32(x14);
r2->d[0] = BE32(x15);

over1 = secp256k1_scalar_check_overflow(r1);
over2 = secp256k1_scalar_check_overflow(r2);
over_count++;
} while (over1 | over2);
}

#undef ROTL32
#undef QUARTERROUND
#undef BE32
#undef LE32

#endif /* SECP256K1_SCALAR_REPR_IMPL_H */
5 changes: 5 additions & 0 deletions src/scalar_low_impl.h
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Expand Up @@ -111,4 +111,9 @@ SECP256K1_INLINE static int secp256k1_scalar_eq(const secp256k1_scalar *a, const
return *a == *b;
}

SECP256K1_INLINE static void secp256k1_scalar_chacha20(secp256k1_scalar *r1, secp256k1_scalar *r2, const unsigned char *seed, uint64_t n) {
*r1 = (seed[0] + n) % EXHAUSTIVE_TEST_ORDER;
*r2 = (seed[1] + n) % EXHAUSTIVE_TEST_ORDER;
}

#endif /* SECP256K1_SCALAR_REPR_IMPL_H */
58 changes: 58 additions & 0 deletions src/tests.c
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Expand Up @@ -961,12 +961,70 @@ void scalar_test(void) {

}

void scalar_chacha_tests(void) {
unsigned char expected1[64] = {
0x76, 0xb8, 0xe0, 0xad, 0xa0, 0xf1, 0x3d, 0x90,
0x40, 0x5d, 0x6a, 0xe5, 0x53, 0x86, 0xbd, 0x28,
0xbd, 0xd2, 0x19, 0xb8, 0xa0, 0x8d, 0xed, 0x1a,
0xa8, 0x36, 0xef, 0xcc, 0x8b, 0x77, 0x0d, 0xc7,
0xda, 0x41, 0x59, 0x7c, 0x51, 0x57, 0x48, 0x8d,
0x77, 0x24, 0xe0, 0x3f, 0xb8, 0xd8, 0x4a, 0x37,
0x6a, 0x43, 0xb8, 0xf4, 0x15, 0x18, 0xa1, 0x1c,
0xc3, 0x87, 0xb6, 0x69, 0xb2, 0xee, 0x65, 0x86
};
unsigned char expected2[64] = {
0x45, 0x40, 0xf0, 0x5a, 0x9f, 0x1f, 0xb2, 0x96,
0xd7, 0x73, 0x6e, 0x7b, 0x20, 0x8e, 0x3c, 0x96,
0xeb, 0x4f, 0xe1, 0x83, 0x46, 0x88, 0xd2, 0x60,
0x4f, 0x45, 0x09, 0x52, 0xed, 0x43, 0x2d, 0x41,
0xbb, 0xe2, 0xa0, 0xb6, 0xea, 0x75, 0x66, 0xd2,
0xa5, 0xd1, 0xe7, 0xe2, 0x0d, 0x42, 0xaf, 0x2c,
0x53, 0xd7, 0x92, 0xb1, 0xc4, 0x3f, 0xea, 0x81,
0x7e, 0x9a, 0xd2, 0x75, 0xae, 0x54, 0x69, 0x63
};
unsigned char expected3[64] = {
0x47, 0x4a, 0x4f, 0x35, 0x4f, 0xee, 0x93, 0x59,
0xbb, 0x65, 0x81, 0xe5, 0xd9, 0x15, 0xa6, 0x01,
0xb6, 0x8c, 0x68, 0x03, 0x38, 0xff, 0x65, 0xe6,
0x56, 0x4a, 0x3e, 0x65, 0x59, 0xfc, 0x12, 0x3f,
0xa9, 0xb2, 0xf9, 0x3e, 0x57, 0xc3, 0xa5, 0xcb,
0xe0, 0x72, 0x74, 0x27, 0x88, 0x1c, 0x23, 0xdf,
0xe2, 0xb6, 0xcc, 0xfb, 0x93, 0xed, 0xcb, 0x02,
0xd7, 0x50, 0x52, 0x45, 0x84, 0x88, 0xbb, 0xea
};

secp256k1_scalar exp_r1, exp_r2;
secp256k1_scalar r1, r2;
unsigned char seed1[32] = { 0 };

secp256k1_scalar_chacha20(&r1, &r2, seed1, 0);
secp256k1_scalar_set_b32(&exp_r1, &expected1[0], NULL);
secp256k1_scalar_set_b32(&exp_r2, &expected1[32], NULL);
CHECK(secp256k1_scalar_eq(&exp_r1, &r1));
CHECK(secp256k1_scalar_eq(&exp_r2, &r2));

seed1[31] = 1;
secp256k1_scalar_chacha20(&r1, &r2, seed1, 0);
secp256k1_scalar_set_b32(&exp_r1, &expected2[0], NULL);
secp256k1_scalar_set_b32(&exp_r2, &expected2[32], NULL);
CHECK(secp256k1_scalar_eq(&exp_r1, &r1));
CHECK(secp256k1_scalar_eq(&exp_r2, &r2));

secp256k1_scalar_chacha20(&r1, &r2, seed1, 100);
secp256k1_scalar_set_b32(&exp_r1, &expected3[0], NULL);
secp256k1_scalar_set_b32(&exp_r2, &expected3[32], NULL);
CHECK(secp256k1_scalar_eq(&exp_r1, &r1));
CHECK(secp256k1_scalar_eq(&exp_r2, &r2));
}

void run_scalar_tests(void) {
int i;
for (i = 0; i < 128 * count; i++) {
scalar_test();
}

scalar_chacha_tests();

{
/* (-1)+1 should be zero. */
secp256k1_scalar s, o;
Expand Down

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