///
///  @file rng.h
///  @brief An AES256 CTR DRBG
///
///  Created by Bassham, Lawrence E (Fed) on 8/29/17.
///  Copyright © 2017 Bassham, Lawrence E (Fed). All rights reserved.
///
///  An AES256 CTR DRBG
///

#ifndef rng_h
#define rng_h

#include <stdio.h>

#define RNG_SUCCESS     0
#define RNG_BAD_MAXLEN  -1
#define RNG_BAD_OUTBUF  -2
#define RNG_BAD_REQ_LEN -3

typedef struct {
    unsigned char buffer[16];
    int           buffer_pos;
    unsigned long length_remaining;
    unsigned char key[32];
    unsigned char ctr[16];
} AES_XOF_struct;

typedef struct {
    unsigned char Key[32];
    unsigned char V[16];
    int           reseed_counter;
} AES256_CTR_DRBG_struct;

void AES256_CTR_DRBG_Update(unsigned char *provided_data,
                            unsigned char *Key,
                            unsigned char *V);

int seedexpander_init(AES_XOF_struct *ctx,
                      unsigned char * seed,
                      unsigned char * diversifier,
                      unsigned long   maxlen);

int seedexpander(AES_XOF_struct *ctx, unsigned char *x, unsigned long xlen);

void randombytes_init(unsigned char *entropy_input,
                      unsigned char *personalization_string,
                      int            security_strength);

int randombytes(unsigned char *x, unsigned long long xlen);

void randombytes_init_with_state(AES256_CTR_DRBG_struct *states,
                                 unsigned char *         entropy_input_48bytes);

int randombytes_with_state(AES256_CTR_DRBG_struct *states,
                           unsigned char *         x,
                           unsigned long long      xlen);

#endif /* rng_h */