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- /* Libottery by Nick Mathewson.
-
- This software has been dedicated to the public domain under the CC0
- public domain dedication.
-
- To the extent possible under law, the person who associated CC0 with
- libottery has waived all copyright and related or neighboring rights
- to libottery.
-
- You should have received a copy of the CC0 legalcode along with this
- work in doc/cc0.txt. If not, see
- <http://creativecommons.org/publicdomain/zero/1.0/>.
- */
- #ifndef OTTERY_H_HEADER_INCLUDED_
- #define OTTERY_H_HEADER_INCLUDED_
- #include <stdint.h>
- #include <sys/types.h>
-
- #ifdef __cplusplus
- extern "C" {
- #endif
-
- #include "ottery_common.h"
-
- /** @file */
-
- struct ottery_config;
-
- /* Functions that use an implicit global state */
-
- /**
- * Fill a buffer with random bytes.
- *
- * @param buf The buffer to fill.
- * @param n The number of bytes to write.
- */
- void ottery_rand_bytes(void *buf, size_t n);
- /**
- * Generate a random number of type unsigned.
- *
- * @return A random number between 0 and UINT_MAX included,
- * chosen uniformly.
- */
- unsigned ottery_rand_unsigned(void);
- /**
- * Generate a random number of type uint32_t.
- *
- * @return A random number between 0 and UINT32_MAX included,
- * chosen uniformly.
- */
- uint32_t ottery_rand_uint32(void);
- /**
- * Generate a random number of type uint64_t.
- *
- * @return A random number between 0 and UINT64_MAX included,
- * chosen uniformly.
- */
- uint64_t ottery_rand_uint64(void);
- /**
- * Generate a random number of type unsigned in a given range.
- *
- * @param top The upper bound of the range (inclusive).
- * @return A random number no larger than top, and no less than 0,
- * chosen uniformly.
- */
- unsigned ottery_rand_range(unsigned top);
- /**
- * Generate a random number of type uint64_t in a given range.
- *
- * @param top The upper bound of the range (inclusive).
- * @return A random number no larger than top, and no less than 0,
- * chosen uniformly.
- */
- uint64_t ottery_rand_range64(uint64_t top);
-
- /**
- * Initialize the libottery global state.
- *
- * Most users should not need to use this function. If you use it, you must
- * call it before any of: ottery_rand_bytes, ottery_rand_unsigned,
- * ottery_rand_uint64, ottery_rand_range, ottery_rand_uint64_range,
- * ottery_add_seed, ottery_wipe, ottery_stir.
- *
- * You would want to use this function if you want to select some non-default
- * behavior using an ottery_config structure.
- *
- * @param cfg Either NULL, or an ottery_config structure that has been
- * initialized with ottery_config_init().
- * @return Zero on success, or one of the OTTERY_ERR_* error codes on failure.
- */
- int ottery_init(const struct ottery_config *cfg);
-
- /**
- * Add more entropy to the libottery global state.
- *
- * Calling this function should be needless, if you trust your operating
- * system's random number generator and entropy extraction features. You
- * would want to use this function if you think the operating system's random
- * number generator might be inadequate, and you want to add more entropy from
- * EGD or something.
- *
- * You might also want to call this function if your belief system says that
- * it's useful to periodically add more raw entropy to a well-seeded
- * cryptographically strong PRNG.
- *
- * @param seed Bytes to add to the state. If this value is NULL, we take
- * more random bytes from the OS.
- * @param n The number of bytes to add. If this value is 0, we take more
- * random bytes from the OS, regardless of the value of seed.
- * @return Zero on success, or one of the OTTERY_ERR_* error codes on failure.
- */
- int ottery_add_seed(const uint8_t *seed, size_t n);
-
- /**
- * Destroy the libottery global state and release any resources that it might
- * hold.
- *
- * Ordinarily, you would only want to call this at exit, if at all.
- */
- void ottery_wipe(void);
-
- /**
- * Explicitly tell libottery to prevent backtracking attacks. (Usually
- * needless.)
- *
- * Once this function has been called, an attacker who compromises the state
- * later on will not be able to recover bytes that have previously been
- * returned by any of the ottery_rand_* functions.
- *
- * You should not usually need to call this function: Libottery provides
- * backtracking resistance by default, so unless you have manually recompiled
- * with the OTTERY_NO_CLEAR_AFTER_YIELD option, this function isn't
- * necessary and has no effect. Even *with* OTTERY_NO_CLEAR_AFTER_YIELD,
- * this function isn't necessary in ordinary operation: the libottery state is
- * implicitly "stirred" every 1k or so.
- */
- void ottery_prevent_backtracking(void);
-
- #ifdef __cplusplus
- }
- #endif
-
- #endif
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