Add Chacha20-Poly1305, AES128-GCM and AES256-GCM support (#93) * Add Chacha20-Poly1305 authenticated encryption * Add general AEAD approach. * Add [email protected] algo using LibTomCrypt chacha and poly1305 routines. Chacha20-Poly1305 is generally faster than AES256 on CPU w/o dedicated AES instructions, having the same key size. Compiling in will add ~5,5kB to binary size on x86-64. function old new delta chacha_crypt - 1397 +1397 _poly1305_block - 608 +608 poly1305_done - 595 +595 dropbear_chachapoly_crypt - 457 +457 .rodata 26976 27392 +416 poly1305_process - 290 +290 poly1305_init - 221 +221 chacha_setup - 218 +218 encrypt_packet 1068 1270 +202 dropbear_chachapoly_getlength - 147 +147 decrypt_packet 756 897 +141 chacha_ivctr64 - 137 +137 read_packet 543 637 +94 dropbear_chachapoly_start - 94 +94 read_kex_algos 792 880 +88 chacha_keystream - 69 +69 dropbear_mode_chachapoly - 48 +48 sshciphers 280 320 +40 dropbear_mode_none 24 48 +24 dropbear_mode_ctr 24 48 +24 dropbear_mode_cbc 24 48 +24 dropbear_chachapoly_mac - 24 +24 dropbear_chachapoly - 24 +24 gen_new_keys 848 854 +6 ------------------------------------------------------------------------------ (add/remove: 14/0 grow/shrink: 10/0 up/down: 5388/0) Total: 5388 bytes * Add AES128-GCM and AES256-GCM authenticated encryption * Add general AES-GCM mode. * Add [email protected] and [email protected] algo using LibTomCrypt gcm routines. AES-GCM is combination of AES CTR mode and GHASH, slower than AES-CTR on CPU w/o dedicated AES/GHASH instructions therefore disabled by default. Compiling in will add ~6kB to binary size on x86-64. function old new delta gcm_process - 1060 +1060 .rodata 26976 27808 +832 gcm_gf_mult - 820 +820 gcm_add_aad - 660 +660 gcm_shift_table - 512 +512 gcm_done - 471 +471 gcm_add_iv - 384 +384 gcm_init - 347 +347 dropbear_gcm_crypt - 309 +309 encrypt_packet 1068 1270 +202 decrypt_packet 756 897 +141 gcm_reset - 118 +118 read_packet 543 637 +94 read_kex_algos 792 880 +88 sshciphers 280 360 +80 gcm_mult_h - 80 +80 dropbear_gcm_start - 62 +62 dropbear_mode_gcm - 48 +48 dropbear_mode_none 24 48 +24 dropbear_mode_ctr 24 48 +24 dropbear_mode_cbc 24 48 +24 dropbear_ghash - 24 +24 dropbear_gcm_getlength - 24 +24 gen_new_keys 848 854 +6 ------------------------------------------------------------------------------ (add/remove: 14/0 grow/shrink: 10/0 up/down: 6434/0) Total: 6434 bytes

/* LibTomCrypt, modular cryptographic library -- Tom St Denis
 *
 * LibTomCrypt is a library that provides various cryptographic
 * algorithms in a highly modular and flexible manner.
 *
 * The library is free for all purposes without any express
 * guarantee it works.
 */
#include "tomcrypt.h"

#if defined(LTC_MRSA) || (!defined(LTC_NO_MATH) && !defined(LTC_NO_PRNGS))

/**
  @file rand_prime.c
  Generate a random prime, Tom St Denis
*/

#define USE_BBS 1

int rand_prime(void *N, long len, prng_state *prng, int wprng)
{
   int            err, res, type;
   unsigned char *buf;

   LTC_ARGCHK(N != NULL);

   /* get type */
   if (len < 0) {
      type = USE_BBS;
      len = -len;
   } else {
      type = 0;
   }

   /* allow sizes between 2 and 512 bytes for a prime size */
   if (len < 2 || len > 512) {
      return CRYPT_INVALID_PRIME_SIZE;
   }

   /* valid PRNG? Better be! */
   if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
      return err;
   }

   /* allocate buffer to work with */
   buf = XCALLOC(1, len);
   if (buf == NULL) {
       return CRYPT_MEM;
   }

   do {
      /* generate value */
      if (prng_descriptor[wprng].read(buf, len, prng) != (unsigned long)len) {
         XFREE(buf);
         return CRYPT_ERROR_READPRNG;
      }

      /* munge bits */
      buf[0]     |= 0x80 | 0x40;
      buf[len-1] |= 0x01 | ((type & USE_BBS) ? 0x02 : 0x00);

      /* load value */
      if ((err = mp_read_unsigned_bin(N, buf, len)) != CRYPT_OK) {
         XFREE(buf);
         return err;
      }

      /* test */
      if ((err = mp_prime_is_prime(N, LTC_MILLER_RABIN_REPS, &res)) != CRYPT_OK) {
         XFREE(buf);
         return err;
      }
   } while (res == LTC_MP_NO);

#ifdef LTC_CLEAN_STACK
   zeromem(buf, len);
#endif

   XFREE(buf);
   return CRYPT_OK;
}

#endif /* LTC_NO_MATH */


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