xmss-KAT-generator/prg.c

/*
prg.c version 20150811
Andreas Hülsing
Public domain.
*/
#include "chacha.h"
#include "prg.h"
#include <stdio.h>


const unsigned char zero_nonce[12] = {0};

/**
 * Generates rlen output bytes using ChaCha20 with a zero nonce and counter = 0
 */
void prg(unsigned char *r, unsigned long long rlen, const unsigned char *key, unsigned int key_len)
{  
  CRYPTO_chacha_20_keystream(r, rlen, key, zero_nonce, 0);
}

/**
 * Generates rlen output bytes using ChaCha20.
 * Nonce and counter are set depending on the address addr.
 */
void prg_with_counter(unsigned char *r, unsigned long long rlen, const unsigned char *key, unsigned int key_len, const unsigned char addr[16])
{
  int i;
  unsigned char nonce[12];
  if(key_len == 32){
    for(i = 0; i < 12; i++)
    {
      nonce[i] = addr[i];
    }
    uint32_t counter;
    counter = (((uint32_t)addr[12]) << 24)|(((uint32_t)addr[13]) << 16)|(((uint32_t)addr[14]) << 8)|addr[15];
    // TODO: Check address handling. Endianess?
    CRYPTO_chacha_20_keystream(r, rlen, key, nonce, counter);
  } 
  else 
  {
    if(key_len == 64)
    {
      for(i = 0; i < 12; i++)
      {
	nonce[i] = addr[i];
      }
      uint32_t counter;
      counter = (((uint32_t)addr[12]) << 24)|(((uint32_t)addr[13]) << 16)|(((uint32_t)addr[14]) << 8)|addr[15];
      // TODO: WRONG! Uses only 32 byte of key. However, does not compile with HMAC-SHA512
      CRYPTO_chacha_20_keystream(r, rlen, key, nonce, counter);
    } else {
      fprintf(stderr,"prg.c:: Code only supports 32 byte and 64 byte seeds");
    }
  }
}