Mercurial > dropbear
diff libtomcrypt/src/pk/dh/dh_generate_key.c @ 1471:6dba84798cd5
Update to libtomcrypt 1.18.1, merged with Dropbear changes
author | Matt Johnston <matt@ucc.asn.au> |
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date | Fri, 09 Feb 2018 21:44:05 +0800 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/libtomcrypt/src/pk/dh/dh_generate_key.c Fri Feb 09 21:44:05 2018 +0800 @@ -0,0 +1,102 @@ +/* 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" + +#ifdef LTC_MDH + +static int _dh_groupsize_to_keysize(int groupsize) +{ + /* The strength estimates from https://tools.ietf.org/html/rfc3526#section-8 + * We use "Estimate 2" to get an appropriate private key (exponent) size. + */ + if (groupsize <= 0) { + return 0; + } + else if (groupsize <= 192) { + return 30; /* 1536-bit => key size 240-bit */ + } + else if (groupsize <= 256) { + return 40; /* 2048-bit => key size 320-bit */ + } + else if (groupsize <= 384) { + return 52; /* 3072-bit => key size 416-bit */ + } + else if (groupsize <= 512) { + return 60; /* 4096-bit => key size 480-bit */ + } + else if (groupsize <= 768) { + return 67; /* 6144-bit => key size 536-bit */ + } + else if (groupsize <= 1024) { + return 77; /* 8192-bit => key size 616-bit */ + } + else { + return 0; + } +} + +int dh_generate_key(prng_state *prng, int wprng, dh_key *key) +{ + unsigned char *buf; + unsigned long keysize; + int err, max_iterations = LTC_PK_MAX_RETRIES; + + LTC_ARGCHK(key != NULL); + LTC_ARGCHK(ltc_mp.name != NULL); + + /* good prng? */ + if ((err = prng_is_valid(wprng)) != CRYPT_OK) { + return err; + } + + keysize = _dh_groupsize_to_keysize(mp_unsigned_bin_size(key->prime)); + if (keysize == 0) { + err = CRYPT_INVALID_KEYSIZE; + goto freemp; + } + + /* allocate buffer */ + buf = XMALLOC(keysize); + if (buf == NULL) { + err = CRYPT_MEM; + goto freemp; + } + + key->type = PK_PRIVATE; + do { + /* make up random buf */ + if (prng_descriptor[wprng].read(buf, keysize, prng) != keysize) { + err = CRYPT_ERROR_READPRNG; + goto freebuf; + } + /* load the x value - private key */ + if ((err = mp_read_unsigned_bin(key->x, buf, keysize)) != CRYPT_OK) { + goto freebuf; + } + /* compute the y value - public key */ + if ((err = mp_exptmod(key->base, key->x, key->prime, key->y)) != CRYPT_OK) { + goto freebuf; + } + err = dh_check_pubkey(key); + } while (err != CRYPT_OK && max_iterations-- > 0); + +freebuf: + zeromem(buf, keysize); + XFREE(buf); +freemp: + if (err != CRYPT_OK) dh_free(key); + return err; +} + +#endif /* LTC_MDH */ + +/* ref: $Format:%D$ */ +/* git commit: $Format:%H$ */ +/* commit time: $Format:%ai$ */