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.
 */

/* The implementation is based on:
 * chacha-ref.c version 20080118
 * Public domain from D. J. Bernstein
 */

#include "tomcrypt.h"

#ifdef LTC_CHACHA

static const char * const sigma = "expand 32-byte k";
static const char * const tau   = "expand 16-byte k";

/**
   Initialize an ChaCha context (only the key)
   @param st        [out] The destination of the ChaCha state
   @param key       The secret key
   @param keylen    The length of the secret key (octets)
   @param rounds    Number of rounds (e.g. 20 for ChaCha20)
   @return CRYPT_OK if successful
*/
int chacha_setup(chacha_state *st, const unsigned char *key, unsigned long keylen, int rounds)
{
   const char *constants;

   LTC_ARGCHK(st  != NULL);
   LTC_ARGCHK(key != NULL);
   LTC_ARGCHK(keylen == 32 || keylen == 16);

   if (rounds == 0) rounds = 20;

   LOAD32L(st->input[4], key + 0);
   LOAD32L(st->input[5], key + 4);
   LOAD32L(st->input[6], key + 8);
   LOAD32L(st->input[7], key + 12);
   if (keylen == 32) { /* 256bit */
      key += 16;
      constants = sigma;
   } else { /* 128bit */
      constants = tau;
   }
   LOAD32L(st->input[8],  key + 0);
   LOAD32L(st->input[9],  key + 4);
   LOAD32L(st->input[10], key + 8);
   LOAD32L(st->input[11], key + 12);
   LOAD32L(st->input[0],  constants + 0);
   LOAD32L(st->input[1],  constants + 4);
   LOAD32L(st->input[2],  constants + 8);
   LOAD32L(st->input[3],  constants + 12);
   st->rounds = rounds; /* e.g. 20 for chacha20 */
   st->ivlen = 0; /* will be set later by chacha_ivctr(32|64) */
   return CRYPT_OK;
}

#endif

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