2 * Copyright 2015-2016 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the OpenSSL license (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
11 #include <openssl/ec.h>
12 #include <openssl/evp.h>
14 /* Key derivation function from X9.62/SECG */
15 /* Way more than we will ever need */
16 #define ECDH_KDF_MAX (1 << 30)
18 int ECDH_KDF_X9_62(unsigned char *out, size_t outlen,
19 const unsigned char *Z, size_t Zlen,
20 const unsigned char *sinfo, size_t sinfolen,
23 EVP_MD_CTX *mctx = NULL;
28 if (sinfolen > ECDH_KDF_MAX || outlen > ECDH_KDF_MAX
29 || Zlen > ECDH_KDF_MAX)
31 mctx = EVP_MD_CTX_new();
34 mdlen = EVP_MD_size(md);
36 unsigned char mtmp[EVP_MAX_MD_SIZE];
37 if (!EVP_DigestInit_ex(mctx, md, NULL))
40 ctr[2] = (i >> 8) & 0xFF;
41 ctr[1] = (i >> 16) & 0xFF;
42 ctr[0] = (i >> 24) & 0xFF;
43 if (!EVP_DigestUpdate(mctx, Z, Zlen))
45 if (!EVP_DigestUpdate(mctx, ctr, sizeof(ctr)))
47 if (!EVP_DigestUpdate(mctx, sinfo, sinfolen))
49 if (outlen >= mdlen) {
50 if (!EVP_DigestFinal(mctx, out, NULL))
57 if (!EVP_DigestFinal(mctx, mtmp, NULL))
59 memcpy(out, mtmp, outlen);
60 OPENSSL_cleanse(mtmp, mdlen);
66 EVP_MD_CTX_free(mctx);