2 * AFsplitter - Anti forensic information splitter
4 * Copyright (C) 2004, Clemens Fruhwirth <clemens@endorphin.org>
5 * Copyright (C) 2009-2012, Red Hat, Inc. All rights reserved.
7 * AFsplitter diffuses information over a large stripe of data,
8 * therefor supporting secure data destruction.
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public License
12 * version 2 as published by the Free Software Foundation.
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU Library General Public License for more details.
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
27 #include <netinet/in.h>
32 static void XORblock(const char *src1, const char *src2, char *dst, size_t n)
36 for(j = 0; j < n; ++j)
37 dst[j] = src1[j] ^ src2[j];
40 static int hash_buf(const char *src, char *dst, uint32_t iv,
41 size_t len, const char *hash_name)
43 struct crypt_hash *hd = NULL;
44 char *iv_char = (char *)&iv;
48 if (crypt_hash_init(&hd, hash_name))
51 if ((r = crypt_hash_write(hd, iv_char, sizeof(uint32_t))))
54 if ((r = crypt_hash_write(hd, src, len)))
57 r = crypt_hash_final(hd, dst, len);
59 crypt_hash_destroy(hd);
63 /* diffuse: Information spreading over the whole dataset with
64 * the help of hash function.
67 static int diffuse(char *src, char *dst, size_t size, const char *hash_name)
69 unsigned int digest_size = crypt_hash_size(hash_name);
70 unsigned int i, blocks, padding;
72 blocks = size / digest_size;
73 padding = size % digest_size;
75 for (i = 0; i < blocks; i++)
76 if(hash_buf(src + digest_size * i,
77 dst + digest_size * i,
78 i, (size_t)digest_size, hash_name))
82 if(hash_buf(src + digest_size * i,
83 dst + digest_size * i,
84 i, (size_t)padding, hash_name))
91 * Information splitting. The amount of data is multiplied by
92 * blocknumbers. The same blocksize and blocknumbers values
93 * must be supplied to AF_merge to recover information.
96 int AF_split(char *src, char *dst, size_t blocksize,
97 unsigned int blocknumbers, const char *hash)
103 if((bufblock = calloc(blocksize, 1)) == NULL) return -ENOMEM;
105 /* process everything except the last block */
106 for(i=0; i<blocknumbers-1; i++) {
107 r = crypt_random_get(NULL, dst+(blocksize*i), blocksize, CRYPT_RND_NORMAL);
110 XORblock(dst+(blocksize*i),bufblock,bufblock,blocksize);
111 if(diffuse(bufblock, bufblock, blocksize, hash))
114 /* the last block is computed */
115 XORblock(src,bufblock,dst+(i*blocksize),blocksize);
122 int AF_merge(char *src, char *dst, size_t blocksize,
123 unsigned int blocknumbers, const char *hash)
129 if((bufblock = calloc(blocksize, 1)) == NULL)
132 memset(bufblock,0,blocksize);
133 for(i=0; i<blocknumbers-1; i++) {
134 XORblock(src+(blocksize*i),bufblock,bufblock,blocksize);
135 if(diffuse(bufblock, bufblock, blocksize, hash))
138 XORblock(src + blocksize * i, bufblock, dst, blocksize);
145 /* Size of final split data including sector alignment */
146 size_t AF_split_sectors(size_t blocksize, unsigned int blocknumbers)
150 /* data material * stripes */
151 af_size = blocksize * blocknumbers;
153 /* round up to sector */
154 af_size = (af_size + (SECTOR_SIZE - 1)) / SECTOR_SIZE;