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Copy pathcrypto_kem_sntrup761_tinyssh.c
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crypto_kem_sntrup761_tinyssh.c
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#include "crypto_kem_sntrup761.h"
#include "haslibntruprime.h"
#ifndef HASLIBNTRUPRIME
/*
Original code: supercop-20210125/crypto_kem/sntrup761/ref
Modifications (Jan Mojzis):
- source code merged into single file
- crypto_kem renamed to crypto_kem_sntrup761_tinyssh
- crypto_declassify added
*/
/* See https://ntruprime.cr.yp.to/software.html for detailed documentation. */
#include <string.h>
#include "crypto_uint64.h"
#include "crypto_uint32.h"
#include "crypto_uint16.h"
#include "crypto_int32.h"
#include "crypto_int16.h"
#include "crypto_int8.h"
#include "randombytes.h"
#include "crypto_verify_32.h"
#include "crypto_sort_uint32.h"
#include "crypto_hash_sha512.h"
#include "crypto_declassify.h"
#define uint64 crypto_uint64
#define uint32 crypto_uint32
#define uint16 crypto_uint16
#define int32 crypto_int32
#define int16 crypto_int16
#define int8 crypto_int8
/* uint32.c */
/*
CPU division instruction typically takes time depending on x.
This software is designed to take time independent of x.
Time still varies depending on m; user must ensure that m is constant.
Time also varies on CPUs where multiplication is variable-time.
There could be more CPU issues.
There could also be compiler issues.
*/
static void uint32_divmod_uint14(uint32 *q, uint16 *r, uint32 x, uint16 m) {
uint32 v = 0x80000000;
uint32 qpart;
uint32 mask;
v /= m;
/* caller guarantees m > 0 */
/* caller guarantees m < 16384 */
/* vm <= 2^31 <= vm+m-1 */
/* xvm <= 2^31 x <= xvm+x(m-1) */
*q = 0;
qpart = (x * (uint64) v) >> 31;
/* 2^31 qpart <= xv <= 2^31 qpart + 2^31-1 */
/* 2^31 qpart m <= xvm <= 2^31 qpart m + (2^31-1)m */
/* 2^31 qpart m <= 2^31 x <= 2^31 qpart m + (2^31-1)m + x(m-1) */
/* 0 <= 2^31 newx <= (2^31-1)m + x(m-1) */
/* 0 <= newx <= (1-1/2^31)m + x(m-1)/2^31 */
/* 0 <= newx <= (1-1/2^31)(2^14-1) + (2^32-1)((2^14-1)-1)/2^31 */
x -= qpart * m;
*q += qpart;
/* x <= 49146 */
qpart = (x * (uint64) v) >> 31;
/* 0 <= newx <= (1-1/2^31)m + x(m-1)/2^31 */
/* 0 <= newx <= m + 49146(2^14-1)/2^31 */
/* 0 <= newx <= m + 0.4 */
/* 0 <= newx <= m */
x -= qpart * m;
*q += qpart;
/* x <= m */
x -= m;
*q += 1;
mask = -(x >> 31);
x += mask & (uint32) m;
*q += mask;
/* x < m */
*r = x;
}
uint32 uint32_div_uint14(uint32 x, uint16 m) {
uint32 q;
uint16 r;
uint32_divmod_uint14(&q, &r, x, m);
return q;
}
uint16 uint32_mod_uint14(uint32 x, uint16 m) {
uint32 q;
uint16 r;
uint32_divmod_uint14(&q, &r, x, m);
return r;
}
/* int32.c */
static void int32_divmod_uint14(int32 *q, uint16 *r, int32 x, uint16 m) {
uint32 uq, uq2;
uint16 ur, ur2;
uint32 mask;
uint32_divmod_uint14(&uq, &ur, 0x80000000 + (uint32) x, m);
uint32_divmod_uint14(&uq2, &ur2, 0x80000000, m);
ur -= ur2;
uq -= uq2;
mask = -(uint32) (ur >> 15);
ur += mask & m;
uq += mask;
*r = ur;
*q = uq;
}
int32 int32_div_uint14(int32 x, uint16 m) {
int32 q;
uint16 r;
int32_divmod_uint14(&q, &r, x, m);
return q;
}
uint16 int32_mod_uint14(int32 x, uint16 m) {
int32 q;
uint16 r;
int32_divmod_uint14(&q, &r, x, m);
return r;
}
/* paramsmenu.h */
/* pick one of these three: */
#define SIZE761
#undef SIZE653
#undef SIZE857
/* pick one of these two: */
#define SNTRUP /* Streamlined NTRU Prime */
#undef LPR /* NTRU LPRime */
/* params.h */
#ifndef params_H
#define params_H
/* menu of parameter choices: */
/* what the menu means: */
#if defined(SIZE761)
#define p 761
#define q 4591
#define Rounded_bytes 1007
#ifndef LPR
#define Rq_bytes 1158
#define w 286
#else
#define w 250
#define tau0 2156
#define tau1 114
#define tau2 2007
#define tau3 287
#endif
#elif defined(SIZE653)
#define p 653
#define q 4621
#define Rounded_bytes 865
#ifndef LPR
#define Rq_bytes 994
#define w 288
#else
#define w 252
#define tau0 2175
#define tau1 113
#define tau2 2031
#define tau3 290
#endif
#elif defined(SIZE857)
#define p 857
#define q 5167
#define Rounded_bytes 1152
#ifndef LPR
#define Rq_bytes 1322
#define w 322
#else
#define w 281
#define tau0 2433
#define tau1 101
#define tau2 2265
#define tau3 324
#endif
#else
#error "no parameter set defined"
#endif
#ifdef LPR
#define I 256
#endif
#endif
/* Decode.c */
static void Decode(uint16 *out, const unsigned char *S, const uint16 *M,
long long len) {
if (len == 1) {
if (M[0] == 1)
*out = 0;
else if (M[0] <= 256)
*out = uint32_mod_uint14(S[0], M[0]);
else
*out = uint32_mod_uint14(S[0] + (((uint16) S[1]) << 8), M[0]);
}
if (len > 1) {
uint16 R2[(len + 1) / 2];
uint16 M2[(len + 1) / 2];
uint16 bottomr[len / 2];
uint32 bottomt[len / 2];
long long i;
for (i = 0; i < len - 1; i += 2) {
uint32 m = M[i] * (uint32) M[i + 1];
if (m > 256 * 16383) {
bottomt[i / 2] = 256 * 256;
bottomr[i / 2] = S[0] + 256 * S[1];
S += 2;
M2[i / 2] = (((m + 255) >> 8) + 255) >> 8;
}
else if (m >= 16384) {
bottomt[i / 2] = 256;
bottomr[i / 2] = S[0];
S += 1;
M2[i / 2] = (m + 255) >> 8;
}
else {
bottomt[i / 2] = 1;
bottomr[i / 2] = 0;
M2[i / 2] = m;
}
}
if (i < len) M2[i / 2] = M[i];
Decode(R2, S, M2, (len + 1) / 2);
for (i = 0; i < len - 1; i += 2) {
uint32 r = bottomr[i / 2];
uint32 r1;
uint16 r0;
r += bottomt[i / 2] * R2[i / 2];
uint32_divmod_uint14(&r1, &r0, r, M[i]);
r1 = uint32_mod_uint14(
r1, M[i + 1]); /* only needed for invalid inputs */
*out++ = r0;
*out++ = r1;
}
if (i < len) *out++ = R2[i / 2];
}
}
/* Encode.c */
/* 0 <= R[i] < M[i] < 16384 */
static void Encode(unsigned char *out, const uint16 *R, const uint16 *M,
long long len) {
if (len == 1) {
uint16 r = R[0];
uint16 m = M[0];
while (m > 1) {
*out++ = r;
r >>= 8;
m = (m + 255) >> 8;
}
}
if (len > 1) {
uint16 R2[(len + 1) / 2];
uint16 M2[(len + 1) / 2];
long long i;
for (i = 0; i < len - 1; i += 2) {
uint32 m0 = M[i];
uint32 r = R[i] + R[i + 1] * m0;
uint32 m = M[i + 1] * m0;
while (m >= 16384) {
*out++ = r;
r >>= 8;
m = (m + 255) >> 8;
}
R2[i / 2] = r;
M2[i / 2] = m;
}
if (i < len) {
R2[i / 2] = R[i];
M2[i / 2] = M[i];
}
Encode(out, R2, M2, (len + 1) / 2);
}
}
/* kem.c */
#ifdef LPR
#endif
/* ----- masks */
#ifndef LPR
/* return -1 if x!=0; else return 0 */
static int int16_nonzero_mask(int16 x) {
uint16 u = x; /* 0, else 1...65535 */
uint32 v = u; /* 0, else 1...65535 */
v = -v; /* 0, else 2^32-65535...2^32-1 */
v >>= 31; /* 0, else 1 */
return -v; /* 0, else -1 */
}
#endif
/* return -1 if x<0; otherwise return 0 */
static int int16_negative_mask(int16 x) {
uint16 u = x;
u >>= 15;
return -(int) u;
/* alternative with gcc -fwrapv: */
/* x>>15 compiles to CPU's arithmetic right shift */
}
/* ----- arithmetic mod 3 */
typedef int8 small;
/* F3 is always represented as -1,0,1 */
/* so ZZ_fromF3 is a no-op */
/* x must not be close to top int16 */
static small F3_freeze(int16 x) { return int32_mod_uint14(x + 1, 3) - 1; }
/* ----- arithmetic mod q */
#define q12 ((q - 1) / 2)
typedef int16 Fq;
/* always represented as -q12...q12 */
/* so ZZ_fromFq is a no-op */
/* x must not be close to top int32 */
static Fq Fq_freeze(int32 x) { return int32_mod_uint14(x + q12, q) - q12; }
#ifndef LPR
static Fq Fq_recip(Fq a1) {
int i = 1;
Fq ai = a1;
while (i < q - 2) {
ai = Fq_freeze(a1 * (int32) ai);
i += 1;
}
return ai;
}
#endif
/* ----- Top and Right */
#ifdef LPR
#define tau 16
static int8 Top(Fq C) { return (tau1 * (int32) (C + tau0) + 16384) >> 15; }
static Fq Right(int8 T) { return Fq_freeze(tau3 * (int32) T - tau2); }
#endif
/* ----- small polynomials */
#ifndef LPR
/* 0 if Weightw_is(r), else -1 */
static int Weightw_mask(small *r) {
int weight = 0;
int i;
for (i = 0; i < p; ++i) weight += r[i] & 1;
return int16_nonzero_mask(weight - w);
}
/* R3_fromR(R_fromRq(r)) */
static void R3_fromRq(small *out, const Fq *r) {
int i;
for (i = 0; i < p; ++i) out[i] = F3_freeze(r[i]);
}
/* h = f*g in the ring R3 */
static void R3_mult(small *h, const small *f, const small *g) {
small fg[p + p - 1];
small result;
int i, j;
for (i = 0; i < p; ++i) {
result = 0;
for (j = 0; j <= i; ++j) result = F3_freeze(result + f[j] * g[i - j]);
fg[i] = result;
}
for (i = p; i < p + p - 1; ++i) {
result = 0;
for (j = i - p + 1; j < p; ++j)
result = F3_freeze(result + f[j] * g[i - j]);
fg[i] = result;
}
for (i = p + p - 2; i >= p; --i) {
fg[i - p] = F3_freeze(fg[i - p] + fg[i]);
fg[i - p + 1] = F3_freeze(fg[i - p + 1] + fg[i]);
}
for (i = 0; i < p; ++i) h[i] = fg[i];
}
/* returns 0 if recip succeeded; else -1 */
static int R3_recip(small *out, const small *in) {
small f[p + 1], g[p + 1], v[p + 1], r[p + 1];
int i, loop, delta;
int sign, swap, t;
for (i = 0; i < p + 1; ++i) v[i] = 0;
for (i = 0; i < p + 1; ++i) r[i] = 0;
r[0] = 1;
for (i = 0; i < p; ++i) f[i] = 0;
f[0] = 1;
f[p - 1] = f[p] = -1;
for (i = 0; i < p; ++i) g[p - 1 - i] = in[i];
g[p] = 0;
delta = 1;
for (loop = 0; loop < 2 * p - 1; ++loop) {
for (i = p; i > 0; --i) v[i] = v[i - 1];
v[0] = 0;
sign = -g[0] * f[0];
swap = int16_negative_mask(-delta) & int16_nonzero_mask(g[0]);
delta ^= swap & (delta ^ -delta);
delta += 1;
for (i = 0; i < p + 1; ++i) {
t = swap & (f[i] ^ g[i]);
f[i] ^= t;
g[i] ^= t;
t = swap & (v[i] ^ r[i]);
v[i] ^= t;
r[i] ^= t;
}
for (i = 0; i < p + 1; ++i) g[i] = F3_freeze(g[i] + sign * f[i]);
for (i = 0; i < p + 1; ++i) r[i] = F3_freeze(r[i] + sign * v[i]);
for (i = 0; i < p; ++i) g[i] = g[i + 1];
g[p] = 0;
}
sign = f[0];
for (i = 0; i < p; ++i) out[i] = sign * v[p - 1 - i];
return int16_nonzero_mask(delta);
}
#endif
/* ----- polynomials mod q */
/* h = f*g in the ring Rq */
static void Rq_mult_small(Fq *h, const Fq *f, const small *g) {
Fq fg[p + p - 1];
Fq result;
int i, j;
for (i = 0; i < p; ++i) {
result = 0;
for (j = 0; j <= i; ++j)
result = Fq_freeze(result + f[j] * (int32) g[i - j]);
fg[i] = result;
}
for (i = p; i < p + p - 1; ++i) {
result = 0;
for (j = i - p + 1; j < p; ++j)
result = Fq_freeze(result + f[j] * (int32) g[i - j]);
fg[i] = result;
}
for (i = p + p - 2; i >= p; --i) {
fg[i - p] = Fq_freeze(fg[i - p] + fg[i]);
fg[i - p + 1] = Fq_freeze(fg[i - p + 1] + fg[i]);
}
for (i = 0; i < p; ++i) h[i] = fg[i];
}
#ifndef LPR
/* h = 3f in Rq */
static void Rq_mult3(Fq *h, const Fq *f) {
int i;
for (i = 0; i < p; ++i) h[i] = Fq_freeze(3 * f[i]);
}
/* out = 1/(3*in) in Rq */
/* returns 0 if recip succeeded; else -1 */
static int Rq_recip3(Fq *out, const small *in) {
Fq f[p + 1], g[p + 1], v[p + 1], r[p + 1];
int i, loop, delta;
int swap, t;
int32 f0, g0;
Fq scale;
for (i = 0; i < p + 1; ++i) v[i] = 0;
for (i = 0; i < p + 1; ++i) r[i] = 0;
r[0] = Fq_recip(3);
for (i = 0; i < p; ++i) f[i] = 0;
f[0] = 1;
f[p - 1] = f[p] = -1;
for (i = 0; i < p; ++i) g[p - 1 - i] = in[i];
g[p] = 0;
delta = 1;
for (loop = 0; loop < 2 * p - 1; ++loop) {
for (i = p; i > 0; --i) v[i] = v[i - 1];
v[0] = 0;
swap = int16_negative_mask(-delta) & int16_nonzero_mask(g[0]);
delta ^= swap & (delta ^ -delta);
delta += 1;
for (i = 0; i < p + 1; ++i) {
t = swap & (f[i] ^ g[i]);
f[i] ^= t;
g[i] ^= t;
t = swap & (v[i] ^ r[i]);
v[i] ^= t;
r[i] ^= t;
}
f0 = f[0];
g0 = g[0];
for (i = 0; i < p + 1; ++i) g[i] = Fq_freeze(f0 * g[i] - g0 * f[i]);
for (i = 0; i < p + 1; ++i) r[i] = Fq_freeze(f0 * r[i] - g0 * v[i]);
for (i = 0; i < p; ++i) g[i] = g[i + 1];
g[p] = 0;
}
scale = Fq_recip(f[0]);
for (i = 0; i < p; ++i) out[i] = Fq_freeze(scale * (int32) v[p - 1 - i]);
return int16_nonzero_mask(delta);
}
#endif
/* ----- rounded polynomials mod q */
static void Round(Fq *out, const Fq *a) {
int i;
for (i = 0; i < p; ++i) out[i] = a[i] - F3_freeze(a[i]);
}
/* ----- sorting to generate short polynomial */
static void Short_fromlist(small *out, const uint32 *in) {
uint32 L[p];
int i;
for (i = 0; i < w; ++i) L[i] = in[i] & (uint32) -2;
for (i = w; i < p; ++i) L[i] = (in[i] & (uint32) -3) | 1;
crypto_sort_uint32(L, p);
for (i = 0; i < p; ++i) out[i] = (L[i] & 3) - 1;
}
/* ----- underlying hash function */
#define Hash_bytes 32
/* e.g., b = 0 means out = Hash0(in) */
static void Hash_prefix(unsigned char *out, int b, const unsigned char *in,
int inlen) {
unsigned char x[inlen + 1];
unsigned char h[64];
int i;
x[0] = b;
for (i = 0; i < inlen; ++i) x[i + 1] = in[i];
crypto_hash_sha512(h, x, inlen + 1);
for (i = 0; i < 32; ++i) out[i] = h[i];
}
/* ----- higher-level randomness */
static uint32 urandom32(void) {
unsigned char c[4];
uint32 out[4];
randombytes(c, 4);
out[0] = (uint32) c[0];
out[1] = ((uint32) c[1]) << 8;
out[2] = ((uint32) c[2]) << 16;
out[3] = ((uint32) c[3]) << 24;
return out[0] + out[1] + out[2] + out[3];
}
static void Short_random(small *out) {
uint32 L[p];
int i;
for (i = 0; i < p; ++i) L[i] = urandom32();
Short_fromlist(out, L);
}
#ifndef LPR
static void Small_random(small *out) {
int i;
for (i = 0; i < p; ++i)
out[i] = (((urandom32() & 0x3fffffff) * 3) >> 30) - 1;
}
#endif
/* ----- Streamlined NTRU Prime Core */
#ifndef LPR
/* h,(f,ginv) = KeyGen() */
static void KeyGen(Fq *h, small *f, small *ginv) {
small g[p];
Fq finv[p];
for (;;) {
int result;
Small_random(g);
result = R3_recip(ginv, g);
crypto_declassify(&result, sizeof result);
if (result == 0) break;
}
Short_random(f);
Rq_recip3(finv, f); /* always works */
Rq_mult_small(h, finv, g);
}
/* c = Encrypt(r,h) */
static void Encrypt(Fq *c, const small *r, const Fq *h) {
Fq hr[p];
Rq_mult_small(hr, h, r);
Round(c, hr);
}
/* r = Decrypt(c,(f,ginv)) */
static void Decrypt(small *r, const Fq *c, const small *f, const small *ginv) {
Fq cf[p];
Fq cf3[p];
small e[p];
small ev[p];
int mask;
int i;
Rq_mult_small(cf, c, f);
Rq_mult3(cf3, cf);
R3_fromRq(e, cf3);
R3_mult(ev, e, ginv);
mask = Weightw_mask(ev); /* 0 if weight w, else -1 */
for (i = 0; i < w; ++i) r[i] = ((ev[i] ^ 1) & ~mask) ^ 1;
for (i = w; i < p; ++i) r[i] = ev[i] & ~mask;
}
#endif
/* ----- NTRU LPRime Core */
#ifdef LPR
/* (G,A),a = KeyGen(G); leaves G unchanged */
static void KeyGen(Fq *A, small *a, const Fq *G) {
Fq aG[p];
Short_random(a);
Rq_mult_small(aG, G, a);
Round(A, aG);
}
/* B,T = Encrypt(r,(G,A),b) */
static void Encrypt(Fq *B, int8 *T, const int8 *r, const Fq *G, const Fq *A,
const small *b) {
Fq bG[p];
Fq bA[p];
int i;
Rq_mult_small(bG, G, b);
Round(B, bG);
Rq_mult_small(bA, A, b);
for (i = 0; i < I; ++i) T[i] = Top(Fq_freeze(bA[i] + r[i] * q12));
}
/* r = Decrypt((B,T),a) */
static void Decrypt(int8 *r, const Fq *B, const int8 *T, const small *a) {
Fq aB[p];
int i;
Rq_mult_small(aB, B, a);
for (i = 0; i < I; ++i)
r[i] = -int16_negative_mask(Fq_freeze(Right(T[i]) - aB[i] + 4 * w + 1));
}
#endif
/* ----- encoding I-bit inputs */
#ifdef LPR
#define Inputs_bytes (I / 8)
typedef int8 Inputs[I]; /* passed by reference */
static void Inputs_encode(unsigned char *s, const Inputs r) {
int i;
for (i = 0; i < Inputs_bytes; ++i) s[i] = 0;
for (i = 0; i < I; ++i) s[i >> 3] |= r[i] << (i & 7);
}
#endif
/* ----- Expand */
#ifdef LPR
static const unsigned char aes_nonce[16] = {0};
static void Expand(uint32 *L, const unsigned char *k) {
int i;
crypto_stream_aes256ctr((unsigned char *) L, 4 * p, aes_nonce, k);
for (i = 0; i < p; ++i) {
uint32 L0 = ((unsigned char *) L)[4 * i];
uint32 L1 = ((unsigned char *) L)[4 * i + 1];
uint32 L2 = ((unsigned char *) L)[4 * i + 2];
uint32 L3 = ((unsigned char *) L)[4 * i + 3];
L[i] = L0 + (L1 << 8) + (L2 << 16) + (L3 << 24);
}
}
#endif
/* ----- Seeds */
#ifdef LPR
#define Seeds_bytes 32
static void Seeds_random(unsigned char *s) { randombytes(s, Seeds_bytes); }
#endif
/* ----- Generator, HashShort */
#ifdef LPR
/* G = Generator(k) */
static void Generator(Fq *G, const unsigned char *k) {
uint32 L[p];
int i;
Expand(L, k);
for (i = 0; i < p; ++i) G[i] = uint32_mod_uint14(L[i], q) - q12;
}
/* out = HashShort(r) */
static void HashShort(small *out, const Inputs r) {
unsigned char s[Inputs_bytes];
unsigned char h[Hash_bytes];
uint32 L[p];
Inputs_encode(s, r);
Hash_prefix(h, 5, s, sizeof s);
Expand(L, h);
Short_fromlist(out, L);
}
#endif
/* ----- NTRU LPRime Expand */
#ifdef LPR
/* (S,A),a = XKeyGen() */
static void XKeyGen(unsigned char *S, Fq *A, small *a) {
Fq G[p];
Seeds_random(S);
Generator(G, S);
KeyGen(A, a, G);
}
/* B,T = XEncrypt(r,(S,A)) */
static void XEncrypt(Fq *B, int8 *T, const int8 *r, const unsigned char *S,
const Fq *A) {
Fq G[p];
small b[p];
Generator(G, S);
HashShort(b, r);
Encrypt(B, T, r, G, A, b);
}
#define XDecrypt Decrypt
#endif
/* ----- encoding small polynomials (including short polynomials) */
#define Small_bytes ((p + 3) / 4)
/* these are the only functions that rely on p mod 4 = 1 */
static void Small_encode(unsigned char *s, const small *f) {
small x;
int i;
for (i = 0; i < p / 4; ++i) {
x = *f++ + 1;
x += (*f++ + 1) << 2;
x += (*f++ + 1) << 4;
x += (*f++ + 1) << 6;
*s++ = x;
}
x = *f++ + 1;
*s++ = x;
}
static void Small_decode(small *f, const unsigned char *s) {
unsigned char x;
int i;
for (i = 0; i < p / 4; ++i) {
x = *s++;
*f++ = ((small) (x & 3)) - 1;
x >>= 2;
*f++ = ((small) (x & 3)) - 1;
x >>= 2;
*f++ = ((small) (x & 3)) - 1;
x >>= 2;
*f++ = ((small) (x & 3)) - 1;
}
x = *s++;
*f++ = ((small) (x & 3)) - 1;
}
/* ----- encoding general polynomials */
#ifndef LPR
static void Rq_encode(unsigned char *s, const Fq *r) {
uint16 R[p], M[p];
int i;
for (i = 0; i < p; ++i) R[i] = r[i] + q12;
for (i = 0; i < p; ++i) M[i] = q;
Encode(s, R, M, p);
}
static void Rq_decode(Fq *r, const unsigned char *s) {
uint16 R[p], M[p];
int i;
for (i = 0; i < p; ++i) M[i] = q;
Decode(R, s, M, p);
for (i = 0; i < p; ++i) r[i] = ((Fq) R[i]) - q12;
}
#endif
/* ----- encoding rounded polynomials */
static void Rounded_encode(unsigned char *s, const Fq *r) {
uint16 R[p], M[p];
int i;
for (i = 0; i < p; ++i) R[i] = ((r[i] + q12) * 10923) >> 15;
for (i = 0; i < p; ++i) M[i] = (q + 2) / 3;
Encode(s, R, M, p);
}
static void Rounded_decode(Fq *r, const unsigned char *s) {
uint16 R[p], M[p];
int i;
for (i = 0; i < p; ++i) M[i] = (q + 2) / 3;
Decode(R, s, M, p);
for (i = 0; i < p; ++i) r[i] = R[i] * 3 - q12;
}
/* ----- encoding top polynomials */
#ifdef LPR
#define Top_bytes (I / 2)
static void Top_encode(unsigned char *s, const int8 *T) {
int i;
for (i = 0; i < Top_bytes; ++i) s[i] = T[2 * i] + (T[2 * i + 1] << 4);
}
static void Top_decode(int8 *T, const unsigned char *s) {
int i;
for (i = 0; i < Top_bytes; ++i) {
T[2 * i] = s[i] & 15;
T[2 * i + 1] = s[i] >> 4;
}
}
#endif
/* ----- Streamlined NTRU Prime Core plus encoding */
#ifndef LPR
typedef small Inputs[p]; /* passed by reference */
#define Inputs_random Short_random
#define Inputs_encode Small_encode
#define Inputs_bytes Small_bytes
#define Ciphertexts_bytes Rounded_bytes
#define SecretKeys_bytes (2 * Small_bytes)
#define PublicKeys_bytes Rq_bytes
/* pk,sk = ZKeyGen() */
static void ZKeyGen(unsigned char *pk, unsigned char *sk) {
Fq h[p];
small f[p], v[p];
KeyGen(h, f, v);
Rq_encode(pk, h);
Small_encode(sk, f);
sk += Small_bytes;
Small_encode(sk, v);
}
/* C = ZEncrypt(r,pk) */
static void ZEncrypt(unsigned char *C, const Inputs r,
const unsigned char *pk) {
Fq h[p];
Fq c[p];
Rq_decode(h, pk);
Encrypt(c, r, h);
Rounded_encode(C, c);
}
/* r = ZDecrypt(C,sk) */
static void ZDecrypt(Inputs r, const unsigned char *C,
const unsigned char *sk) {
small f[p], v[p];
Fq c[p];
Small_decode(f, sk);
sk += Small_bytes;
Small_decode(v, sk);
Rounded_decode(c, C);
Decrypt(r, c, f, v);
}
#endif
/* ----- NTRU LPRime Expand plus encoding */
#ifdef LPR
#define Ciphertexts_bytes (Rounded_bytes + Top_bytes)
#define SecretKeys_bytes Small_bytes
#define PublicKeys_bytes (Seeds_bytes + Rounded_bytes)
static void Inputs_random(Inputs r) {
unsigned char s[Inputs_bytes];
int i;
randombytes(s, sizeof s);
for (i = 0; i < I; ++i) r[i] = 1 & (s[i >> 3] >> (i & 7));
}
/* pk,sk = ZKeyGen() */
static void ZKeyGen(unsigned char *pk, unsigned char *sk) {
Fq A[p];
small a[p];
XKeyGen(pk, A, a);
pk += Seeds_bytes;
Rounded_encode(pk, A);
Small_encode(sk, a);