src/sig/falcon/pqclean_falcon-padded-512_avx2/inner.h

#ifndef FALCON_INNER_H__
#define FALCON_INNER_H__

/*
 * Internal functions for Falcon. This is not the API intended to be
 * used by applications; instead, this internal API provides all the
 * primitives on which wrappers build to provide external APIs.
 *
 * ==========================(LICENSE BEGIN)============================
 *
 * Copyright (c) 2017-2019  Falcon Project
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 * ===========================(LICENSE END)=============================
 *
 * @author   Thomas Pornin <thomas.pornin@nccgroup.com>
 */

/*
 * IMPORTANT API RULES
 * -------------------
 *
 * This API has some non-trivial usage rules:
 *
 *
 *  - All public functions (i.e. the non-static ones) must be referenced
 *    with the PQCLEAN_FALCONPADDED512_AVX2_ macro (e.g. PQCLEAN_FALCONPADDED512_AVX2_verify_raw for the verify_raw()
 *    function). That macro adds a prefix to the name, which is
 *    configurable with the FALCON_PREFIX macro. This allows compiling
 *    the code into a specific "namespace" and potentially including
 *    several versions of this code into a single application (e.g. to
 *    have an AVX2 and a non-AVX2 variants and select the one to use at
 *    runtime based on availability of AVX2 opcodes).
 *
 *  - Functions that need temporary buffers expects them as a final
 *    tmp[] array of type uint8_t*, with a size which is documented for
 *    each function. However, most have some alignment requirements,
 *    because they will use the array to store 16-bit, 32-bit or 64-bit
 *    values (e.g. uint64_t or double). The caller must ensure proper
 *    alignment. What happens on unaligned access depends on the
 *    underlying architecture, ranging from a slight time penalty
 *    to immediate termination of the process.
 *
 *  - Some functions rely on specific rounding rules and precision for
 *    floating-point numbers. On some systems (in particular 32-bit x86
 *    with the 387 FPU), this requires setting an hardware control
 *    word. The caller MUST use set_fpu_cw() to ensure proper precision:
 *
 *      oldcw = set_fpu_cw(2);
 *      PQCLEAN_FALCONPADDED512_AVX2_sign_dyn(...);
 *      set_fpu_cw(oldcw);
 *
 *    On systems where the native floating-point precision is already
 *    proper, or integer-based emulation is used, the set_fpu_cw()
 *    function does nothing, so it can be called systematically.
 */

#include <stdint.h>
#include <stdlib.h>
#include <string.h>

/*
 * This implementation uses AVX2 and optionally FMA intrinsics.
 */
#include <immintrin.h>
#define FMADD(a, b, c)   _mm256_add_pd(_mm256_mul_pd(a, b), c)
#define FMSUB(a, b, c)   _mm256_sub_pd(_mm256_mul_pd(a, b), c)

/*
 * Some computations with floating-point elements, in particular
 * rounding to the nearest integer, rely on operations using _exactly_
 * the precision of IEEE-754 binary64 type (i.e. 52 bits). On 32-bit
 * x86, the 387 FPU may be used (depending on the target OS) and, in
 * that case, may use more precision bits (i.e. 64 bits, for an 80-bit
 * total type length); to prevent miscomputations, we define an explicit
 * function that modifies the precision in the FPU control word.
 *
 * set_fpu_cw() sets the precision to the provided value, and returns
 * the previously set precision; callers are supposed to restore the
 * previous precision on exit. The correct (52-bit) precision is
 * configured with the value "2". On unsupported compilers, or on
 * targets other than 32-bit x86, or when the native 'double' type is
 * not used, the set_fpu_cw() function does nothing at all.
 */
static inline unsigned
set_fpu_cw(unsigned x) {
    return x;
}

/* ==================================================================== */
/*
 * SHAKE256 implementation (shake.c).
 *
 * API is defined to be easily replaced with the fips202.h API defined
 * as part of PQClean.
 */

#include "fips202.h"

#define inner_shake256_context                shake256incctx
#define inner_shake256_init(sc)               shake256_inc_init(sc)
#define inner_shake256_inject(sc, in, len)    shake256_inc_absorb(sc, in, len)
#define inner_shake256_flip(sc)               shake256_inc_finalize(sc)
#define inner_shake256_extract(sc, out, len)  shake256_inc_squeeze(out, len, sc)
#define inner_shake256_ctx_release(sc)        shake256_inc_ctx_release(sc)

/* ==================================================================== */
/*
 * Encoding/decoding functions (codec.c).
 *
 * Encoding functions take as parameters an output buffer (out) with
 * a given maximum length (max_out_len); returned value is the actual
 * number of bytes which have been written. If the output buffer is
 * not large enough, then 0 is returned (some bytes may have been
 * written to the buffer). If 'out' is NULL, then 'max_out_len' is
 * ignored; instead, the function computes and returns the actual
 * required output length (in bytes).
 *
 * Decoding functions take as parameters an input buffer (in) with
 * its maximum length (max_in_len); returned value is the actual number
 * of bytes that have been read from the buffer. If the provided length
 * is too short, then 0 is returned.
 *
 * Values to encode or decode are vectors of integers, with N = 2^logn
 * elements.
 *
 * Three encoding formats are defined:
 *
 *   - modq: sequence of values modulo 12289, each encoded over exactly
 *     14 bits. The encoder and decoder verify that integers are within
 *     the valid range (0..12288). Values are arrays of uint16.
 *
 *   - trim: sequence of signed integers, a specified number of bits
 *     each. The number of bits is provided as parameter and includes
 *     the sign bit. Each integer x must be such that |x| < 2^(bits-1)
 *     (which means that the -2^(bits-1) value is forbidden); encode and
 *     decode functions check that property. Values are arrays of
 *     int16_t or int8_t, corresponding to names 'trim_i16' and
 *     'trim_i8', respectively.
 *
 *   - comp: variable-length encoding for signed integers; each integer
 *     uses a minimum of 9 bits, possibly more. This is normally used
 *     only for signatures.
 *
 */

size_t PQCLEAN_FALCONPADDED512_AVX2_modq_encode(void *out, size_t max_out_len,
        const uint16_t *x, unsigned logn);
size_t PQCLEAN_FALCONPADDED512_AVX2_trim_i16_encode(void *out, size_t max_out_len,
        const int16_t *x, unsigned logn, unsigned bits);
size_t PQCLEAN_FALCONPADDED512_AVX2_trim_i8_encode(void *out, size_t max_out_len,
        const int8_t *x, unsigned logn, unsigned bits);
size_t PQCLEAN_FALCONPADDED512_AVX2_comp_encode(void *out, size_t max_out_len,
        const int16_t *x, unsigned logn);

size_t PQCLEAN_FALCONPADDED512_AVX2_modq_decode(uint16_t *x, unsigned logn,
        const void *in, size_t max_in_len);
size_t PQCLEAN_FALCONPADDED512_AVX2_trim_i16_decode(int16_t *x, unsigned logn, unsigned bits,
        const void *in, size_t max_in_len);
size_t PQCLEAN_FALCONPADDED512_AVX2_trim_i8_decode(int8_t *x, unsigned logn, unsigned bits,
        const void *in, size_t max_in_len);
size_t PQCLEAN_FALCONPADDED512_AVX2_comp_decode(int16_t *x, unsigned logn,
        const void *in, size_t max_in_len);

/*
 * Number of bits for key elements, indexed by logn (1 to 10). This
 * is at most 8 bits for all degrees, but some degrees may have shorter
 * elements.
 */
extern const uint8_t PQCLEAN_FALCONPADDED512_AVX2_max_fg_bits[];
extern const uint8_t PQCLEAN_FALCONPADDED512_AVX2_max_FG_bits[];

/*
 * Maximum size, in bits, of elements in a signature, indexed by logn
 * (1 to 10). The size includes the sign bit.
 */
extern const uint8_t PQCLEAN_FALCONPADDED512_AVX2_max_sig_bits[];

/* ==================================================================== */
/*
 * Support functions used for both signature generation and signature
 * verification (common.c).
 */

/*
 * From a SHAKE256 context (must be already flipped), produce a new
 * point. This is the non-constant-time version, which may leak enough
 * information to serve as a stop condition on a brute force attack on
 * the hashed message (provided that the nonce value is known).
 */
void PQCLEAN_FALCONPADDED512_AVX2_hash_to_point_vartime(inner_shake256_context *sc,
        uint16_t *x, unsigned logn);

/*
 * From a SHAKE256 context (must be already flipped), produce a new
 * point. The temporary buffer (tmp) must have room for 2*2^logn bytes.
 * This function is constant-time but is typically more expensive than
 * PQCLEAN_FALCONPADDED512_AVX2_hash_to_point_vartime().
 *
 * tmp[] must have 16-bit alignment.
 */
void PQCLEAN_FALCONPADDED512_AVX2_hash_to_point_ct(inner_shake256_context *sc,
        uint16_t *x, unsigned logn, uint8_t *tmp);

/*
 * Tell whether a given vector (2N coordinates, in two halves) is
 * acceptable as a signature. This compares the appropriate norm of the
 * vector with the acceptance bound. Returned value is 1 on success
 * (vector is short enough to be acceptable), 0 otherwise.
 */
int PQCLEAN_FALCONPADDED512_AVX2_is_short(const int16_t *s1, const int16_t *s2, unsigned logn);

/*
 * Tell whether a given vector (2N coordinates, in two halves) is
 * acceptable as a signature. Instead of the first half s1, this
 * function receives the "saturated squared norm" of s1, i.e. the
 * sum of the squares of the coordinates of s1 (saturated at 2^32-1
 * if the sum exceeds 2^31-1).
 *
 * Returned value is 1 on success (vector is short enough to be
 * acceptable), 0 otherwise.
 */
int PQCLEAN_FALCONPADDED512_AVX2_is_short_half(uint32_t sqn, const int16_t *s2, unsigned logn);

/* ==================================================================== */
/*
 * Signature verification functions (vrfy.c).
 */

/*
 * Convert a public key to NTT + Montgomery format. Conversion is done
 * in place.
 */
void PQCLEAN_FALCONPADDED512_AVX2_to_ntt_monty(uint16_t *h, unsigned logn);

/*
 * Internal signature verification code:
 *   c0[]      contains the hashed nonce+message
 *   s2[]      is the decoded signature
 *   h[]       contains the public key, in NTT + Montgomery format
 *   logn      is the degree log
 *   tmp[]     temporary, must have at least 2*2^logn bytes
 * Returned value is 1 on success, 0 on error.
 *
 * tmp[] must have 16-bit alignment.
 */
int PQCLEAN_FALCONPADDED512_AVX2_verify_raw(const uint16_t *c0, const int16_t *s2,
        const uint16_t *h, unsigned logn, uint8_t *tmp);

/*
 * Compute the public key h[], given the private key elements f[] and
 * g[]. This computes h = g/f mod phi mod q, where phi is the polynomial
 * modulus. This function returns 1 on success, 0 on error (an error is
 * reported if f is not invertible mod phi mod q).
 *
 * The tmp[] array must have room for at least 2*2^logn elements.
 * tmp[] must have 16-bit alignment.
 */
int PQCLEAN_FALCONPADDED512_AVX2_compute_public(uint16_t *h,
        const int8_t *f, const int8_t *g, unsigned logn, uint8_t *tmp);

/*
 * Recompute the fourth private key element. Private key consists in
 * four polynomials with small coefficients f, g, F and G, which are
 * such that fG - gF = q mod phi; furthermore, f is invertible modulo
 * phi and modulo q. This function recomputes G from f, g and F.
 *
 * The tmp[] array must have room for at least 4*2^logn bytes.
 *
 * Returned value is 1 in success, 0 on error (f not invertible).
 * tmp[] must have 16-bit alignment.
 */
int PQCLEAN_FALCONPADDED512_AVX2_complete_private(int8_t *G,
        const int8_t *f, const int8_t *g, const int8_t *F,
        unsigned logn, uint8_t *tmp);

/*
 * Test whether a given polynomial is invertible modulo phi and q.
 * Polynomial coefficients are small integers.
 *
 * tmp[] must have 16-bit alignment.
 */
int PQCLEAN_FALCONPADDED512_AVX2_is_invertible(
    const int16_t *s2, unsigned logn, uint8_t *tmp);

/*
 * Count the number of elements of value zero in the NTT representation
 * of the given polynomial: this is the number of primitive 2n-th roots
 * of unity (modulo q = 12289) that are roots of the provided polynomial
 * (taken modulo q).
 *
 * tmp[] must have 16-bit alignment.
 */
int PQCLEAN_FALCONPADDED512_AVX2_count_nttzero(const int16_t *sig, unsigned logn, uint8_t *tmp);

/*
 * Internal signature verification with public key recovery:
 *   h[]       receives the public key (NOT in NTT/Montgomery format)
 *   c0[]      contains the hashed nonce+message
 *   s1[]      is the first signature half
 *   s2[]      is the second signature half
 *   logn      is the degree log
 *   tmp[]     temporary, must have at least 2*2^logn bytes
 * Returned value is 1 on success, 0 on error. Success is returned if
 * the signature is a short enough vector; in that case, the public
 * key has been written to h[]. However, the caller must still
 * verify that h[] is the correct value (e.g. with regards to a known
 * hash of the public key).
 *
 * h[] may not overlap with any of the other arrays.
 *
 * tmp[] must have 16-bit alignment.
 */
int PQCLEAN_FALCONPADDED512_AVX2_verify_recover(uint16_t *h,
        const uint16_t *c0, const int16_t *s1, const int16_t *s2,
        unsigned logn, uint8_t *tmp);

/* ==================================================================== */
/*
 * Implementation of floating-point real numbers (fpr.h, fpr.c).
 */

/*
 * Real numbers are implemented by an extra header file, included below.
 * This is meant to support pluggable implementations. The default
 * implementation relies on the C type 'double'.
 *
 * The included file must define the following types, functions and
 * constants:
 *
 *   fpr
 *         type for a real number
 *
 *   fpr fpr_of(int64_t i)
 *         cast an integer into a real number; source must be in the
 *         -(2^63-1)..+(2^63-1) range
 *
 *   fpr fpr_scaled(int64_t i, int sc)
 *         compute i*2^sc as a real number; source 'i' must be in the
 *         -(2^63-1)..+(2^63-1) range
 *
 *   fpr fpr_ldexp(fpr x, int e)
 *         compute x*2^e
 *
 *   int64_t fpr_rint(fpr x)
 *         round x to the nearest integer; x must be in the -(2^63-1)
 *         to +(2^63-1) range
 *
 *   int64_t fpr_trunc(fpr x)
 *         round to an integer; this rounds towards zero; value must
 *         be in the -(2^63-1) to +(2^63-1) range
 *
 *   fpr fpr_add(fpr x, fpr y)
 *         compute x + y
 *
 *   fpr fpr_sub(fpr x, fpr y)
 *         compute x - y
 *
 *   fpr fpr_neg(fpr x)
 *         compute -x
 *
 *   fpr fpr_half(fpr x)
 *         compute x/2
 *
 *   fpr fpr_double(fpr x)
 *         compute x*2
 *
 *   fpr fpr_mul(fpr x, fpr y)
 *         compute x * y
 *
 *   fpr fpr_sqr(fpr x)
 *         compute x * x
 *
 *   fpr fpr_inv(fpr x)
 *         compute 1/x
 *
 *   fpr fpr_div(fpr x, fpr y)
 *         compute x/y
 *
 *   fpr fpr_sqrt(fpr x)
 *         compute the square root of x
 *
 *   int fpr_lt(fpr x, fpr y)
 *         return 1 if x < y, 0 otherwise
 *
 *   uint64_t fpr_expm_p63(fpr x)
 *         return exp(x), assuming that 0 <= x < log(2). Returned value
 *         is scaled to 63 bits (i.e. it really returns 2^63*exp(-x),
 *         rounded to the nearest integer). Computation should have a
 *         precision of at least 45 bits.
 *
 *   const fpr fpr_gm_tab[]
 *         array of constants for FFT / iFFT
 *
 *   const fpr fpr_p2_tab[]
 *         precomputed powers of 2 (by index, 0 to 10)
 *
 * Constants of type 'fpr':
 *
 *   fpr fpr_q                 12289
 *   fpr fpr_inverse_of_q      1/12289
 *   fpr fpr_inv_2sqrsigma0    1/(2*(1.8205^2))
 *   fpr fpr_inv_sigma[]       1/sigma (indexed by logn, 1 to 10)
 *   fpr fpr_sigma_min[]       1/sigma_min (indexed by logn, 1 to 10)
 *   fpr fpr_log2              log(2)
 *   fpr fpr_inv_log2          1/log(2)
 *   fpr fpr_bnorm_max         16822.4121
 *   fpr fpr_zero              0
 *   fpr fpr_one               1
 *   fpr fpr_two               2
 *   fpr fpr_onehalf           0.5
 *   fpr fpr_ptwo31            2^31
 *   fpr fpr_ptwo31m1          2^31-1
 *   fpr fpr_mtwo31m1          -(2^31-1)
 *   fpr fpr_ptwo63m1          2^63-1
 *   fpr fpr_mtwo63m1          -(2^63-1)
 *   fpr fpr_ptwo63            2^63
 */
#include "fpr.h"

/* ==================================================================== */
/*
 * RNG (rng.c).
 *
 * A PRNG based on ChaCha20 is implemented; it is seeded from a SHAKE256
 * context (flipped) and is used for bulk pseudorandom generation.
 * A system-dependent seed generator is also provided.
 */

/*
 * Obtain a random seed from the system RNG.
 *
 * Returned value is 1 on success, 0 on error.
 */
int PQCLEAN_FALCONPADDED512_AVX2_get_seed(void *seed, size_t seed_len);

/*
 * Structure for a PRNG. This includes a large buffer so that values
 * get generated in advance. The 'state' is used to keep the current
 * PRNG algorithm state (contents depend on the selected algorithm).
 *
 * The unions with 'dummy_u64' are there to ensure proper alignment for
 * 64-bit direct access.
 */
typedef struct {
    union {
        uint8_t d[512]; /* MUST be 512, exactly */
        uint64_t dummy_u64;
    } buf;
    size_t ptr;
    union {
        uint8_t d[256];
        uint64_t dummy_u64;
    } state;
    int type;
} prng;

/*
 * Instantiate a PRNG. That PRNG will feed over the provided SHAKE256
 * context (in "flipped" state) to obtain its initial state.
 */
void PQCLEAN_FALCONPADDED512_AVX2_prng_init(prng *p, inner_shake256_context *src);

/*
 * Refill the PRNG buffer. This is normally invoked automatically, and
 * is declared here only so that prng_get_u64() may be inlined.
 */
void PQCLEAN_FALCONPADDED512_AVX2_prng_refill(prng *p);

/*
 * Get some bytes from a PRNG.
 */
void PQCLEAN_FALCONPADDED512_AVX2_prng_get_bytes(prng *p, void *dst, size_t len);

/*
 * Get a 64-bit random value from a PRNG.
 */
static inline uint64_t
prng_get_u64(prng *p) {
    size_t u;

    /*
     * If there are less than 9 bytes in the buffer, we refill it.
     * This means that we may drop the last few bytes, but this allows
     * for faster extraction code. Also, it means that we never leave
     * an empty buffer.
     */
    u = p->ptr;
    if (u >= (sizeof p->buf.d) - 9) {
        PQCLEAN_FALCONPADDED512_AVX2_prng_refill(p);
        u = 0;
    }
    p->ptr = u + 8;

    return (uint64_t)p->buf.d[u + 0]
           | ((uint64_t)p->buf.d[u + 1] << 8)
           | ((uint64_t)p->buf.d[u + 2] << 16)
           | ((uint64_t)p->buf.d[u + 3] << 24)
           | ((uint64_t)p->buf.d[u + 4] << 32)
           | ((uint64_t)p->buf.d[u + 5] << 40)
           | ((uint64_t)p->buf.d[u + 6] << 48)
           | ((uint64_t)p->buf.d[u + 7] << 56);
}

/*
 * Get an 8-bit random value from a PRNG.
 */
static inline unsigned
prng_get_u8(prng *p) {
    unsigned v;

    v = p->buf.d[p->ptr ++];
    if (p->ptr == sizeof p->buf.d) {
        PQCLEAN_FALCONPADDED512_AVX2_prng_refill(p);
    }
    return v;
}

/* ==================================================================== */
/*
 * FFT (falcon-fft.c).
 *
 * A real polynomial is represented as an array of N 'fpr' elements.
 * The FFT representation of a real polynomial contains N/2 complex
 * elements; each is stored as two real numbers, for the real and
 * imaginary parts, respectively. See falcon-fft.c for details on the
 * internal representation.
 */

/*
 * Compute FFT in-place: the source array should contain a real
 * polynomial (N coefficients); its storage area is reused to store
 * the FFT representation of that polynomial (N/2 complex numbers).
 *
 * 'logn' MUST lie between 1 and 10 (inclusive).
 */
void PQCLEAN_FALCONPADDED512_AVX2_FFT(fpr *f, unsigned logn);

/*
 * Compute the inverse FFT in-place: the source array should contain the
 * FFT representation of a real polynomial (N/2 elements); the resulting
 * real polynomial (N coefficients of type 'fpr') is written over the
 * array.
 *
 * 'logn' MUST lie between 1 and 10 (inclusive).
 */
void PQCLEAN_FALCONPADDED512_AVX2_iFFT(fpr *f, unsigned logn);

/*
 * Add polynomial b to polynomial a. a and b MUST NOT overlap. This
 * function works in both normal and FFT representations.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_add(fpr *a, const fpr *b, unsigned logn);

/*
 * Subtract polynomial b from polynomial a. a and b MUST NOT overlap. This
 * function works in both normal and FFT representations.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_sub(fpr *a, const fpr *b, unsigned logn);

/*
 * Negate polynomial a. This function works in both normal and FFT
 * representations.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_neg(fpr *a, unsigned logn);

/*
 * Compute adjoint of polynomial a. This function works only in FFT
 * representation.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_adj_fft(fpr *a, unsigned logn);

/*
 * Multiply polynomial a with polynomial b. a and b MUST NOT overlap.
 * This function works only in FFT representation.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_mul_fft(fpr *a, const fpr *b, unsigned logn);

/*
 * Multiply polynomial a with the adjoint of polynomial b. a and b MUST NOT
 * overlap. This function works only in FFT representation.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_muladj_fft(fpr *a, const fpr *b, unsigned logn);

/*
 * Multiply polynomial with its own adjoint. This function works only in FFT
 * representation.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_mulselfadj_fft(fpr *a, unsigned logn);

/*
 * Multiply polynomial with a real constant. This function works in both
 * normal and FFT representations.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_mulconst(fpr *a, fpr x, unsigned logn);

/*
 * Divide polynomial a by polynomial b, modulo X^N+1 (FFT representation).
 * a and b MUST NOT overlap.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_div_fft(fpr *a, const fpr *b, unsigned logn);

/*
 * Given f and g (in FFT representation), compute 1/(f*adj(f)+g*adj(g))
 * (also in FFT representation). Since the result is auto-adjoint, all its
 * coordinates in FFT representation are real; as such, only the first N/2
 * values of d[] are filled (the imaginary parts are skipped).
 *
 * Array d MUST NOT overlap with either a or b.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_invnorm2_fft(fpr *d,
        const fpr *a, const fpr *b, unsigned logn);

/*
 * Given F, G, f and g (in FFT representation), compute F*adj(f)+G*adj(g)
 * (also in FFT representation). Destination d MUST NOT overlap with
 * any of the source arrays.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_add_muladj_fft(fpr *d,
        const fpr *F, const fpr *G,
        const fpr *f, const fpr *g, unsigned logn);

/*
 * Multiply polynomial a by polynomial b, where b is autoadjoint. Both
 * a and b are in FFT representation. Since b is autoadjoint, all its
 * FFT coefficients are real, and the array b contains only N/2 elements.
 * a and b MUST NOT overlap.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_mul_autoadj_fft(fpr *a,
        const fpr *b, unsigned logn);

/*
 * Divide polynomial a by polynomial b, where b is autoadjoint. Both
 * a and b are in FFT representation. Since b is autoadjoint, all its
 * FFT coefficients are real, and the array b contains only N/2 elements.
 * a and b MUST NOT overlap.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_div_autoadj_fft(fpr *a,
        const fpr *b, unsigned logn);

/*
 * Perform an LDL decomposition of an auto-adjoint matrix G, in FFT
 * representation. On input, g00, g01 and g11 are provided (where the
 * matrix G = [[g00, g01], [adj(g01), g11]]). On output, the d00, l10
 * and d11 values are written in g00, g01 and g11, respectively
 * (with D = [[d00, 0], [0, d11]] and L = [[1, 0], [l10, 1]]).
 * (In fact, d00 = g00, so the g00 operand is left unmodified.)
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_LDL_fft(const fpr *g00,
        fpr *g01, fpr *g11, unsigned logn);

/*
 * Perform an LDL decomposition of an auto-adjoint matrix G, in FFT
 * representation. This is identical to poly_LDL_fft() except that
 * g00, g01 and g11 are unmodified; the outputs d11 and l10 are written
 * in two other separate buffers provided as extra parameters.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_LDLmv_fft(fpr *d11, fpr *l10,
        const fpr *g00, const fpr *g01,
        const fpr *g11, unsigned logn);

/*
 * Apply "split" operation on a polynomial in FFT representation:
 * f = f0(x^2) + x*f1(x^2), for half-size polynomials f0 and f1
 * (polynomials modulo X^(N/2)+1). f0, f1 and f MUST NOT overlap.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_split_fft(fpr *f0, fpr *f1,
        const fpr *f, unsigned logn);

/*
 * Apply "merge" operation on two polynomials in FFT representation:
 * given f0 and f1, polynomials moduo X^(N/2)+1, this function computes
 * f = f0(x^2) + x*f1(x^2), in FFT representation modulo X^N+1.
 * f MUST NOT overlap with either f0 or f1.
 */
void PQCLEAN_FALCONPADDED512_AVX2_poly_merge_fft(fpr *f,
        const fpr *f0, const fpr *f1, unsigned logn);

/* ==================================================================== */
/*
 * Key pair generation.
 */

/*
 * Required sizes of the temporary buffer (in bytes).
 *
 * This size is 28*2^logn bytes, except for degrees 2 and 4 (logn = 1
 * or 2) where it is slightly greater.
 */
#define FALCON_KEYGEN_TEMP_1      136
#define FALCON_KEYGEN_TEMP_2      272
#define FALCON_KEYGEN_TEMP_3      224
#define FALCON_KEYGEN_TEMP_4      448
#define FALCON_KEYGEN_TEMP_5      896
#define FALCON_KEYGEN_TEMP_6     1792
#define FALCON_KEYGEN_TEMP_7     3584
#define FALCON_KEYGEN_TEMP_8     7168
#define FALCON_KEYGEN_TEMP_9    14336
#define FALCON_KEYGEN_TEMP_10   28672

/*
 * Generate a new key pair. Randomness is extracted from the provided
 * SHAKE256 context, which must have already been seeded and flipped.
 * The tmp[] array must have suitable size (see FALCON_KEYGEN_TEMP_*
 * macros) and be aligned for the uint32_t, uint64_t and fpr types.
 *
 * The private key elements are written in f, g, F and G, and the
 * public key is written in h. Either or both of G and h may be NULL,
 * in which case the corresponding element is not returned (they can
 * be recomputed from f, g and F).
 *
 * tmp[] must have 64-bit alignment.
 * This function uses floating-point rounding (see set_fpu_cw()).
 */
void PQCLEAN_FALCONPADDED512_AVX2_keygen(inner_shake256_context *rng,
        int8_t *f, int8_t *g, int8_t *F, int8_t *G, uint16_t *h,
        unsigned logn, uint8_t *tmp);

/* ==================================================================== */
/*
 * Signature generation.
 */

/*
 * Expand a private key into the B0 matrix in FFT representation and
 * the LDL tree. All the values are written in 'expanded_key', for
 * a total of (8*logn+40)*2^logn bytes.
 *
 * The tmp[] array must have room for at least 48*2^logn bytes.
 *
 * tmp[] must have 64-bit alignment.
 * This function uses floating-point rounding (see set_fpu_cw()).
 */
void PQCLEAN_FALCONPADDED512_AVX2_expand_privkey(fpr *expanded_key,
        const int8_t *f, const int8_t *g, const int8_t *F, const int8_t *G,
        unsigned logn, uint8_t *tmp);

/*
 * Compute a signature over the provided hashed message (hm); the
 * signature value is one short vector. This function uses an
 * expanded key (as generated by PQCLEAN_FALCONPADDED512_AVX2_expand_privkey()).
 *
 * The sig[] and hm[] buffers may overlap.
 *
 * On successful output, the start of the tmp[] buffer contains the s1
 * vector (as int16_t elements).
 *
 * The minimal size (in bytes) of tmp[] is 48*2^logn bytes.
 *
 * tmp[] must have 64-bit alignment.
 * This function uses floating-point rounding (see set_fpu_cw()).
 */
void PQCLEAN_FALCONPADDED512_AVX2_sign_tree(int16_t *sig, inner_shake256_context *rng,
        const fpr *expanded_key,
        const uint16_t *hm, unsigned logn, uint8_t *tmp);

/*
 * Compute a signature over the provided hashed message (hm); the
 * signature value is one short vector. This function uses a raw
 * key and dynamically recompute the B0 matrix and LDL tree; this
 * saves RAM since there is no needed for an expanded key, but
 * increases the signature cost.
 *
 * The sig[] and hm[] buffers may overlap.
 *
 * On successful output, the start of the tmp[] buffer contains the s1
 * vector (as int16_t elements).
 *
 * The minimal size (in bytes) of tmp[] is 72*2^logn bytes.
 *
 * tmp[] must have 64-bit alignment.
 * This function uses floating-point rounding (see set_fpu_cw()).
 */
void PQCLEAN_FALCONPADDED512_AVX2_sign_dyn(int16_t *sig, inner_shake256_context *rng,
        const int8_t *f, const int8_t *g,
        const int8_t *F, const int8_t *G,
        const uint16_t *hm, unsigned logn, uint8_t *tmp);

/*
 * Internal sampler engine. Exported for tests.
 *
 * sampler_context wraps around a source of random numbers (PRNG) and
 * the sigma_min value (nominally dependent on the degree).
 *
 * sampler() takes as parameters:
 *   ctx      pointer to the sampler_context structure
 *   mu       center for the distribution
 *   isigma   inverse of the distribution standard deviation
 * It returns an integer sampled along the Gaussian distribution centered
 * on mu and of standard deviation sigma = 1/isigma.
 *
 * gaussian0_sampler() takes as parameter a pointer to a PRNG, and
 * returns an integer sampled along a half-Gaussian with standard
 * deviation sigma0 = 1.8205 (center is 0, returned value is
 * nonnegative).
 */

typedef struct {
    prng p;
    fpr sigma_min;
} sampler_context;

int PQCLEAN_FALCONPADDED512_AVX2_sampler(void *ctx, fpr mu, fpr isigma);

int PQCLEAN_FALCONPADDED512_AVX2_gaussian0_sampler(prng *p);

/* ==================================================================== */

#endif