56 lines
1.5 KiB
C
56 lines
1.5 KiB
C
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/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org
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*/
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#include "mycrypt.h"
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/* v1.5 Encryption Padding for PKCS #1 -- Tom St Denis */
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#ifdef PKCS_1
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int pkcs_1_v15_es_encode(const unsigned char *msg, unsigned long msglen,
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unsigned long modulus_bitlen,
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prng_state *prng, int prng_idx,
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unsigned char *out, unsigned long *outlen)
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{
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unsigned long modulus_bytelen, x, y;
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_ARGCHK(msg != NULL);
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_ARGCHK(out != NULL);
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_ARGCHK(outlen != NULL);
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/* get modulus len */
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modulus_bytelen = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
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if (modulus_bytelen < 12) {
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return CRYPT_INVALID_ARG;
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}
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/* verify length */
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if (msglen > (modulus_bytelen - 11) || *outlen < modulus_bytelen) {
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return CRYPT_PK_INVALID_SIZE;
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}
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/* 0x00 0x02 PS 0x00 M */
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x = 0;
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out[x++] = 0x00;
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out[x++] = 0x02;
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y = modulus_bytelen - msglen - 3;
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if (prng_descriptor[prng_idx].read(out+x, y, prng) != y) {
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return CRYPT_ERROR_READPRNG;
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}
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x += y;
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out[x++] = 0x00;
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memcpy(out+x, msg, msglen);
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*outlen = modulus_bytelen;
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return CRYPT_OK;
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}
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#endif /* PKCS_1 */
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