2 Copyright (c) 2010 Werner Dittmann
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32 * @brief A Skein API and its functions.
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
40 * The functions enable applications to create a normal Skein hashes and
41 * message authentication codes (MAC).
43 * Using these functions is simple and straight forward:
47 * #include "skein_api.h"
50 * struct skein_ctx ctx; // a Skein hash or MAC context
52 * // prepare context, here for a Skein with a state size of 512 bits.
53 * skein_ctx_prepare(&ctx, SKEIN_512);
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);
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);
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);
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.
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.
81 #include <linux/types.h>
85 * Which Skein size to use
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 */
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
103 u64 x_save[SKEIN_MAX_STATE_WORDS]; /* save area for state variables */
105 struct skein_ctx_hdr h;
106 struct skein_256_ctx s256;
107 struct skein_512_ctx s512;
108 struct skein_1024_ctx s1024;
113 * Prepare a Skein context.
115 * An application must call this function before it can use the Skein
116 * context. The functions clears memory and initializes size dependent
120 * Pointer to a Skein context.
122 * Which Skein size to use.
124 * SKEIN_SUCESS of SKEIN_FAIL
126 int skein_ctx_prepare(struct skein_ctx *ctx, enum skein_size size);
129 * Initialize a Skein context.
131 * Initializes the context with this data and saves the resulting Skein
132 * state variables for further use.
135 * Pointer to a Skein context.
136 * @param hash_bit_len
137 * Number of MAC hash bits to compute
139 * SKEIN_SUCESS of SKEIN_FAIL
142 int skein_init(struct skein_ctx *ctx, size_t hash_bit_len);
145 * Resets a Skein context for further use.
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.
152 * Pointer to a pre-initialized Skein MAC context
154 void skein_reset(struct skein_ctx *ctx);
157 * Initializes a Skein context for MAC usage.
159 * Initializes the context with this data and saves the resulting Skein
160 * state variables for further use.
162 * Applications call the normal Skein functions to update the MAC and
163 * get the final result.
166 * Pointer to an empty or preinitialized Skein MAC context
168 * Pointer to key bytes or NULL
170 * Length of the key in bytes or zero
171 * @param hash_bit_len
172 * Number of MAC hash bits to compute
174 * SKEIN_SUCESS of SKEIN_FAIL
176 int skein_mac_init(struct skein_ctx *ctx, const u8 *key, size_t key_len,
177 size_t hash_bit_len);
180 * Update Skein with the next part of the message.
183 * Pointer to initialized Skein context
185 * Pointer to the message.
186 * @param msg_byte_cnt
187 * Length of the message in @b bytes
189 * Success or error code.
191 int skein_update(struct skein_ctx *ctx, const u8 *msg,
192 size_t msg_byte_cnt);
195 * Update the hash with a message bit string.
197 * Skein can handle data not only as bytes but also as bit strings of
198 * arbitrary length (up to its maximum design size).
201 * Pointer to initialized Skein context
203 * Pointer to the message.
205 * Length of the message in @b bits.
207 int skein_update_bits(struct skein_ctx *ctx, const u8 *msg,
211 * Finalize Skein and return the hash.
213 * Before an application can reuse a Skein setup the application must
214 * reset the Skein context.
217 * Pointer to initialized Skein context
219 * Pointer to buffer that receives the hash. The buffer must be large
220 * enough to store @c hash_bit_len bits.
222 * Success or error code.
225 int skein_final(struct skein_ctx *ctx, u8 *hash);