|
- /* $OpenBSD: sntrup761.c,v 1.6 2023/01/11 02:13:52 djm Exp $ */
-
- /*
- * Public Domain, Authors:
- * - Daniel J. Bernstein
- * - Chitchanok Chuengsatiansup
- * - Tanja Lange
- * - Christine van Vredendaal
- */
-
- #include "includes.h"
-
- #ifdef USE_SNTRUP761X25519
-
- #include <string.h>
- #include "crypto_api.h"
-
- #define int8 crypto_int8
- #define uint8 crypto_uint8
- #define int16 crypto_int16
- #define uint16 crypto_uint16
- #define int32 crypto_int32
- #define uint32 crypto_uint32
- #define int64 crypto_int64
- #define uint64 crypto_uint64
-
- /* from supercop-20201130/crypto_sort/int32/portable4/int32_minmax.inc */
- #define int32_MINMAX(a,b) \
- do { \
- int64_t ab = (int64_t)b ^ (int64_t)a; \
- int64_t c = (int64_t)b - (int64_t)a; \
- c ^= ab & (c ^ b); \
- c >>= 31; \
- c &= ab; \
- a ^= c; \
- b ^= c; \
- } while(0)
-
- /* from supercop-20201130/crypto_sort/int32/portable4/sort.c */
-
-
- static void crypto_sort_int32(void *array,long long n)
- {
- long long top,p,q,r,i,j;
- int32 *x = array;
-
- if (n < 2) return;
- top = 1;
- while (top < n - top) top += top;
-
- for (p = top;p >= 1;p >>= 1) {
- i = 0;
- while (i + 2 * p <= n) {
- for (j = i;j < i + p;++j)
- int32_MINMAX(x[j],x[j+p]);
- i += 2 * p;
- }
- for (j = i;j < n - p;++j)
- int32_MINMAX(x[j],x[j+p]);
-
- i = 0;
- j = 0;
- for (q = top;q > p;q >>= 1) {
- if (j != i) for (;;) {
- if (j == n - q) goto done;
- int32 a = x[j + p];
- for (r = q;r > p;r >>= 1)
- int32_MINMAX(a,x[j + r]);
- x[j + p] = a;
- ++j;
- if (j == i + p) {
- i += 2 * p;
- break;
- }
- }
- while (i + p <= n - q) {
- for (j = i;j < i + p;++j) {
- int32 a = x[j + p];
- for (r = q;r > p;r >>= 1)
- int32_MINMAX(a,x[j+r]);
- x[j + p] = a;
- }
- i += 2 * p;
- }
- /* now i + p > n - q */
- j = i;
- while (j < n - q) {
- int32 a = x[j + p];
- for (r = q;r > p;r >>= 1)
- int32_MINMAX(a,x[j+r]);
- x[j + p] = a;
- ++j;
- }
-
- done: ;
- }
- }
- }
-
- /* from supercop-20201130/crypto_sort/uint32/useint32/sort.c */
-
- /* can save time by vectorizing xor loops */
- /* can save time by integrating xor loops with int32_sort */
-
- static void crypto_sort_uint32(void *array,long long n)
- {
- crypto_uint32 *x = array;
- long long j;
- for (j = 0;j < n;++j) x[j] ^= 0x80000000;
- crypto_sort_int32(array,n);
- for (j = 0;j < n;++j) x[j] ^= 0x80000000;
- }
-
- /* from supercop-20201130/crypto_kem/sntrup761/ref/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;
- }
-
-
- static uint16 uint32_mod_uint14(uint32 x,uint16 m)
- {
- uint32 q;
- uint16 r;
- uint32_divmod_uint14(&q,&r,x,m);
- return r;
- }
-
- /* from supercop-20201130/crypto_kem/sntrup761/ref/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;
- }
-
-
- static uint16 int32_mod_uint14(int32 x,uint16 m)
- {
- int32 q;
- uint16 r;
- int32_divmod_uint14(&q,&r,x,m);
- return r;
- }
-
- /* from supercop-20201130/crypto_kem/sntrup761/ref/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 */
-
- /* from supercop-20201130/crypto_kem/sntrup761/ref/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
-
- /* from supercop-20201130/crypto_kem/sntrup761/ref/Decode.h */
- #ifndef Decode_H
- #define Decode_H
-
-
- /* Decode(R,s,M,len) */
- /* assumes 0 < M[i] < 16384 */
- /* produces 0 <= R[i] < M[i] */
-
- #endif
-
- /* from supercop-20201130/crypto_kem/sntrup761/ref/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];
- }
- }
-
- /* from supercop-20201130/crypto_kem/sntrup761/ref/Encode.h */
- #ifndef Encode_H
- #define Encode_H
-
-
- /* Encode(s,R,M,len) */
- /* assumes 0 <= R[i] < M[i] < 16384 */
-
- #endif
-
- /* from supercop-20201130/crypto_kem/sntrup761/ref/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);
- }
- }
-
- /* from supercop-20201130/crypto_kem/sntrup761/ref/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 (;;) {
- Small_random(g);
- if (R3_recip(ginv,g) == 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);
- }
-
- /* c = ZEncrypt(r,pk) */
- static void ZEncrypt(unsigned char *c,const Inputs r,const unsigned char *pk)
- {
- Fq A[p];
- Fq B[p];
- int8 T[I];
-
- Rounded_decode(A,pk+Seeds_bytes);
- XEncrypt(B,T,r,pk,A);
- Rounded_encode(c,B); c += Rounded_bytes;
- Top_encode(c,T);
- }
-
- /* r = ZDecrypt(C,sk) */
- static void ZDecrypt(Inputs r,const unsigned char *c,const unsigned char *sk)
- {
- small a[p];
- Fq B[p];
- int8 T[I];
-
- Small_decode(a,sk);
- Rounded_decode(B,c);
- Top_decode(T,c+Rounded_bytes);
- XDecrypt(r,B,T,a);
- }
-
- #endif
-
- /* ----- confirmation hash */
-
- #define Confirm_bytes 32
-
- /* h = HashConfirm(r,pk,cache); cache is Hash4(pk) */
- static void HashConfirm(unsigned char *h,const unsigned char *r,const unsigned char *pk,const unsigned char *cache)
- {
- #ifndef LPR
- unsigned char x[Hash_bytes*2];
- int i;
-
- Hash_prefix(x,3,r,Inputs_bytes);
- for (i = 0;i < Hash_bytes;++i) x[Hash_bytes+i] = cache[i];
- #else
- unsigned char x[Inputs_bytes+Hash_bytes];
- int i;
-
- for (i = 0;i < Inputs_bytes;++i) x[i] = r[i];
- for (i = 0;i < Hash_bytes;++i) x[Inputs_bytes+i] = cache[i];
- #endif
- Hash_prefix(h,2,x,sizeof x);
- }
-
- /* ----- session-key hash */
-
- /* k = HashSession(b,y,z) */
- static void HashSession(unsigned char *k,int b,const unsigned char *y,const unsigned char *z)
- {
- #ifndef LPR
- unsigned char x[Hash_bytes+Ciphertexts_bytes+Confirm_bytes];
- int i;
-
- Hash_prefix(x,3,y,Inputs_bytes);
- for (i = 0;i < Ciphertexts_bytes+Confirm_bytes;++i) x[Hash_bytes+i] = z[i];
- #else
- unsigned char x[Inputs_bytes+Ciphertexts_bytes+Confirm_bytes];
- int i;
-
- for (i = 0;i < Inputs_bytes;++i) x[i] = y[i];
- for (i = 0;i < Ciphertexts_bytes+Confirm_bytes;++i) x[Inputs_bytes+i] = z[i];
- #endif
- Hash_prefix(k,b,x,sizeof x);
- }
-
- /* ----- Streamlined NTRU Prime and NTRU LPRime */
-
- /* pk,sk = KEM_KeyGen() */
- static void KEM_KeyGen(unsigned char *pk,unsigned char *sk)
- {
- int i;
-
- ZKeyGen(pk,sk); sk += SecretKeys_bytes;
- for (i = 0;i < PublicKeys_bytes;++i) *sk++ = pk[i];
- randombytes(sk,Inputs_bytes); sk += Inputs_bytes;
- Hash_prefix(sk,4,pk,PublicKeys_bytes);
- }
-
- /* c,r_enc = Hide(r,pk,cache); cache is Hash4(pk) */
- static void Hide(unsigned char *c,unsigned char *r_enc,const Inputs r,const unsigned char *pk,const unsigned char *cache)
- {
- Inputs_encode(r_enc,r);
- ZEncrypt(c,r,pk); c += Ciphertexts_bytes;
- HashConfirm(c,r_enc,pk,cache);
- }
-
- /* c,k = Encap(pk) */
- static void Encap(unsigned char *c,unsigned char *k,const unsigned char *pk)
- {
- Inputs r;
- unsigned char r_enc[Inputs_bytes];
- unsigned char cache[Hash_bytes];
-
- Hash_prefix(cache,4,pk,PublicKeys_bytes);
- Inputs_random(r);
- Hide(c,r_enc,r,pk,cache);
- HashSession(k,1,r_enc,c);
- }
-
- /* 0 if matching ciphertext+confirm, else -1 */
- static int Ciphertexts_diff_mask(const unsigned char *c,const unsigned char *c2)
- {
- uint16 differentbits = 0;
- int len = Ciphertexts_bytes+Confirm_bytes;
-
- while (len-- > 0) differentbits |= (*c++)^(*c2++);
- return (1&((differentbits-1)>>8))-1;
- }
-
- /* k = Decap(c,sk) */
- static void Decap(unsigned char *k,const unsigned char *c,const unsigned char *sk)
- {
- const unsigned char *pk = sk + SecretKeys_bytes;
- const unsigned char *rho = pk + PublicKeys_bytes;
- const unsigned char *cache = rho + Inputs_bytes;
- Inputs r;
- unsigned char r_enc[Inputs_bytes];
- unsigned char cnew[Ciphertexts_bytes+Confirm_bytes];
- int mask;
- int i;
-
- ZDecrypt(r,c,sk);
- Hide(cnew,r_enc,r,pk,cache);
- mask = Ciphertexts_diff_mask(c,cnew);
- for (i = 0;i < Inputs_bytes;++i) r_enc[i] ^= mask&(r_enc[i]^rho[i]);
- HashSession(k,1+mask,r_enc,c);
- }
-
- /* ----- crypto_kem API */
-
-
- int crypto_kem_sntrup761_keypair(unsigned char *pk,unsigned char *sk)
- {
- KEM_KeyGen(pk,sk);
- return 0;
- }
-
- int crypto_kem_sntrup761_enc(unsigned char *c,unsigned char *k,const unsigned char *pk)
- {
- Encap(c,k,pk);
- return 0;
- }
-
- int crypto_kem_sntrup761_dec(unsigned char *k,const unsigned char *c,const unsigned char *sk)
- {
- Decap(k,c,sk);
- return 0;
- }
- #endif /* USE_SNTRUP761X25519 */
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