2 * Copyright (C) 2008, Damien Miller
3 * Copyright (C) 2011, Alex Hornung
5 * Permission to use, copy, and modify this software with or without fee
6 * is hereby granted, provided that this entire notice is included in
7 * all copies of any software which is or includes a copy or
8 * modification of this software.
9 * You may use this code under the GNU public license if you so wish. Please
10 * contribute changes back to the authors under this freer than GPL license
11 * so that we may further the use of strong encryption without limitations to
14 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
15 * IMPLIED WARRANTY. IN PARTICULAR, NONE OF THE AUTHORS MAKES ANY
16 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
17 * MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
28 #include "generic_xts.h"
33 xts_reinit(struct xts_ctx *ctx, u_int64_t blocknum)
38 * Prepare tweak as E_k2(IV). IV is specified as LE representation
39 * of a 64-bit block number which we allow to be passed in directly.
41 for (i = 0; i < XTS_IVSIZE; i++) {
42 ctx->tweak[i] = blocknum & 0xff;
45 /* Last 64 bits of IV are always zero */
46 bzero(ctx->tweak + XTS_IVSIZE, XTS_IVSIZE);
48 return ctx->encrypt_fn(ctx->ctx2, ctx->blk_sz, ctx->tweak, ctx->tweak);
52 xts_crypt(struct xts_ctx *ctx, u_int8_t *data, u_int do_encrypt)
54 u_int8_t block[XTS_MAX_BLOCKSIZE];
55 u_int i, carry_in, carry_out;
58 for (i = 0; i < ctx->blk_sz; i++)
59 block[i] = data[i] ^ ctx->tweak[i];
62 err = ctx->encrypt_fn(ctx->ctx1, ctx->blk_sz, block, data);
64 err = ctx->decrypt_fn(ctx->ctx1, ctx->blk_sz, block, data);
69 for (i = 0; i < ctx->blk_sz; i++)
70 data[i] ^= ctx->tweak[i];
72 /* Exponentiate tweak */
74 for (i = 0; i < ctx->blk_sz; i++) {
75 carry_out = ctx->tweak[i] & 0x80;
76 ctx->tweak[i] = (ctx->tweak[i] << 1) | (carry_in ? 1 : 0);
80 ctx->tweak[0] ^= XTS_ALPHA;
83 bzero(block, sizeof(block));
88 xts_init(struct xts_ctx *ctx, void *arg1, void *arg2, set_key_fn _set_key_fn,
89 zero_key_fn _zero_key_fn, encrypt_decrypt_fn _encrypt_fn,
90 encrypt_decrypt_fn _decrypt_fn, u_int blk_sz, u_int8_t *key, int len)
94 if (len != 32 && len != 64)
98 ctx->encrypt_fn = _encrypt_fn;
99 ctx->decrypt_fn = _decrypt_fn;
100 ctx->set_key_fn = _set_key_fn;
101 ctx->zero_key_fn = _zero_key_fn;
103 err = ctx->set_key_fn(&ctx->ctx1, arg1, arg2, key, len * 4);
107 err = ctx->set_key_fn(&ctx->ctx2, arg1, arg2, key + (len / 2),
110 ctx->zero_key_fn(&ctx->ctx1);
118 xts_encrypt(struct xts_ctx *ctx, u_int8_t *data, size_t len, uint8_t *iv)
120 uint64_t sector = *((uint64_t *)iv);
123 if ((len % ctx->blk_sz) != 0)
126 err = xts_reinit(ctx, sector);
131 err = xts_crypt(ctx, data, 1);
143 xts_decrypt(struct xts_ctx *ctx, u_int8_t *data, size_t len, uint8_t *iv)
145 uint64_t sector = *((uint64_t *)iv);
148 if ((len % ctx->blk_sz) != 0)
151 err = xts_reinit(ctx, sector);
156 err = xts_crypt(ctx, data, 0);
168 xts_uninit(struct xts_ctx *ctx)
170 ctx->zero_key_fn(&ctx->ctx1);
171 ctx->zero_key_fn(&ctx->ctx2);