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"

/**
  @file dsa_shared_secret.c
  DSA Crypto, Tom St Denis
*/

#ifdef LTC_MDSA

/**
  Create a DSA shared secret between two keys
  @param private_key      The private DSA key (the exponent)
  @param base             The base of the exponentiation (allows this to be used for both encrypt and decrypt)
  @param public_key       The public key
  @param out              [out] Destination of the shared secret
  @param outlen           [in/out] The max size and resulting size of the shared secret
  @return CRYPT_OK if successful
*/
int dsa_shared_secret(void          *private_key, void *base,
                      dsa_key       *public_key,
                      unsigned char *out,         unsigned long *outlen)
{
   unsigned long  x;
   void          *res;
   int            err;

   LTC_ARGCHK(private_key != NULL);
   LTC_ARGCHK(public_key  != NULL);
   LTC_ARGCHK(out         != NULL);
   LTC_ARGCHK(outlen      != NULL);

   /* make new point */
   if ((err = mp_init(&res)) != CRYPT_OK) {
      return err;
   }

   if ((err = mp_exptmod(base, private_key, public_key->p, res)) != CRYPT_OK) {
      mp_clear(res);
      return err;
   }

   x = (unsigned long)mp_unsigned_bin_size(res);
   if (*outlen < x) {
      *outlen = x;
      err = CRYPT_BUFFER_OVERFLOW;
      goto done;
   }
   zeromem(out, x);
   if ((err = mp_to_unsigned_bin(res, out + (x - mp_unsigned_bin_size(res))))   != CRYPT_OK)          { goto done; }

   err     = CRYPT_OK;
   *outlen = x;
done:
   mp_clear(res);
   return err;
}

#endif
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/* git commit:  $Format:%H$ */
/* commit time: $Format:%ai$ */