1/*
2Copyright (c) 2010 Werner Dittmann
3
4Permission is hereby granted, free of charge, to any person
5obtaining a copy of this software and associated documentation
6files (the "Software"), to deal in the Software without
7restriction, including without limitation the rights to use,
8copy, modify, merge, publish, distribute, sublicense, and/or sell
9copies of the Software, and to permit persons to whom the
10Software is furnished to do so, subject to the following
11conditions:
12
13The above copyright notice and this permission notice shall be
14included in all copies or substantial portions of the Software.
15
16THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
17EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
18OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
19NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
20HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
21WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
22FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
23OTHER DEALINGS IN THE SOFTWARE.
24
25*/
26
27#ifndef SKEINAPI_H
28#define SKEINAPI_H
29
30/**
31 * @file skein_api.h
32 * @brief A Skein API and its functions.
33 * @{
34 *
35 * This API and the functions that implement this API simplify the usage
36 * of Skein. The design and the way to use the functions follow the openSSL
37 * design but at the same time take care of some Skein specific behaviour
38 * and possibilities.
39 *
40 * The functions enable applications to create a normal Skein hashes and
41 * message authentication codes (MAC).
42 *
43 * Using these functions is simple and straight forward:
44 *
45 * @code
46 *
47 * #include "skein_api.h"
48 *
49 * ...
50 * struct skein_ctx ctx;             // a Skein hash or MAC context
51 *
52 * // prepare context, here for a Skein with a state size of 512 bits.
53 * skein_ctx_prepare(&ctx, SKEIN_512);
54 *
55 * // Initialize the context to set the requested hash length in bits
56 * // here request a output hash size of 31 bits (Skein supports variable
57 * // output sizes even very strange sizes)
58 * skein_init(&ctx, 31);
59 *
60 * // Now update Skein with any number of message bits. A function that
61 * // takes a number of bytes is also available.
62 * skein_update_bits(&ctx, message, msg_length);
63 *
64 * // Now get the result of the Skein hash. The output buffer must be
65 * // large enough to hold the request number of output bits. The application
66 * // may now extract the bits.
67 * skein_final(&ctx, result);
68 * ...
69 * @endcode
70 *
71 * An application may use @c skein_reset to reset a Skein context and use
72 * it for creation of another hash with the same Skein state size and output
73 * bit length. In this case the API implementation restores some internal
74 * internal state data and saves a full Skein initialization round.
75 *
76 * To create a MAC the application just uses @c skein_mac_init instead of
77 * @c skein_init. All other functions calls remain the same.
78 *
79 */
80
81#include <linux/types.h>
82#include "skein_base.h"
83
84/**
85 * Which Skein size to use
86 */
87enum skein_size {
88	SKEIN_256 = 256,     /*!< Skein with 256 bit state */
89	SKEIN_512 = 512,     /*!< Skein with 512 bit state */
90	SKEIN_1024 = 1024    /*!< Skein with 1024 bit state */
91};
92
93/**
94 * Context for Skein.
95 *
96 * This structure was setup with some know-how of the internal
97 * Skein structures, in particular ordering of header and size dependent
98 * variables. If Skein implementation changes this, then adapt these
99 * structures as well.
100 */
101struct skein_ctx {
102	u64 skein_size;
103	u64 x_save[SKEIN_MAX_STATE_WORDS];   /* save area for state variables */
104	union {
105		struct skein_ctx_hdr h;
106		struct skein_256_ctx s256;
107		struct skein_512_ctx s512;
108		struct skein_1024_ctx s1024;
109	} m;
110};
111
112/**
113 * Prepare a Skein context.
114 *
115 * An application must call this function before it can use the Skein
116 * context. The functions clears memory and initializes size dependent
117 * variables.
118 *
119 * @param ctx
120 *     Pointer to a Skein context.
121 * @param size
122 *     Which Skein size to use.
123 * @return
124 *     SKEIN_SUCESS of SKEIN_FAIL
125 */
126int skein_ctx_prepare(struct skein_ctx *ctx, enum skein_size size);
127
128/**
129 * Initialize a Skein context.
130 *
131 * Initializes the context with this data and saves the resulting Skein
132 * state variables for further use.
133 *
134 * @param ctx
135 *     Pointer to a Skein context.
136 * @param hash_bit_len
137 *     Number of MAC hash bits to compute
138 * @return
139 *     SKEIN_SUCESS of SKEIN_FAIL
140 * @see skein_reset
141 */
142int skein_init(struct skein_ctx *ctx, size_t hash_bit_len);
143
144/**
145 * Resets a Skein context for further use.
146 *
147 * Restores the saved chaining variables to reset the Skein context.
148 * Thus applications can reuse the same setup to  process several
149 * messages. This saves a complete Skein initialization cycle.
150 *
151 * @param ctx
152 *     Pointer to a pre-initialized Skein MAC context
153 */
154void skein_reset(struct skein_ctx *ctx);
155
156/**
157 * Initializes a Skein context for MAC usage.
158 *
159 * Initializes the context with this data and saves the resulting Skein
160 * state variables for further use.
161 *
162 * Applications call the normal Skein functions to update the MAC and
163 * get the final result.
164 *
165 * @param ctx
166 *     Pointer to an empty or preinitialized Skein MAC context
167 * @param key
168 *     Pointer to key bytes or NULL
169 * @param key_len
170 *     Length of the key in bytes or zero
171 * @param hash_bit_len
172 *     Number of MAC hash bits to compute
173 * @return
174 *     SKEIN_SUCESS of SKEIN_FAIL
175 */
176int skein_mac_init(struct skein_ctx *ctx, const u8 *key, size_t key_len,
177		   size_t hash_bit_len);
178
179/**
180 * Update Skein with the next part of the message.
181 *
182 * @param ctx
183 *     Pointer to initialized Skein context
184 * @param msg
185 *     Pointer to the message.
186 * @param msg_byte_cnt
187 *     Length of the message in @b bytes
188 * @return
189 *     Success or error code.
190 */
191int skein_update(struct skein_ctx *ctx, const u8 *msg,
192		 size_t msg_byte_cnt);
193
194/**
195 * Update the hash with a message bit string.
196 *
197 * Skein can handle data not only as bytes but also as bit strings of
198 * arbitrary length (up to its maximum design size).
199 *
200 * @param ctx
201 *     Pointer to initialized Skein context
202 * @param msg
203 *     Pointer to the message.
204 * @param msg_bit_cnt
205 *     Length of the message in @b bits.
206 */
207int skein_update_bits(struct skein_ctx *ctx, const u8 *msg,
208		      size_t msg_bit_cnt);
209
210/**
211 * Finalize Skein and return the hash.
212 *
213 * Before an application can reuse a Skein setup the application must
214 * reset the Skein context.
215 *
216 * @param ctx
217 *     Pointer to initialized Skein context
218 * @param hash
219 *     Pointer to buffer that receives the hash. The buffer must be large
220 *     enough to store @c hash_bit_len bits.
221 * @return
222 *     Success or error code.
223 * @see skein_reset
224 */
225int skein_final(struct skein_ctx *ctx, u8 *hash);
226
227/**
228 * @}
229 */
230#endif
231