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* \file psa/crypto_entropy_driver.h
* \brief PSA entropy source driver module
* This header declares types and function signatures for entropy sources.
* This file is part of the PSA Crypto Driver Model, containing functions for
* driver developers to implement to enable hardware to be called in a
* standardized way by a PSA Cryptographic API implementation. The functions
* comprising the driver model, which driver authors implement, are not
* intended to be called by application developers.
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
#include "crypto_driver_common.h"
#ifdef __cplusplus
extern "C" {
/** \defgroup driver_rng Entropy Generation
/** \brief Initialize an entropy driver
* \param[in,out] p_context A hardware-specific structure
* containing any context information for
* the implementation
* \retval #PSA_SUCCESS
typedef psa_status_t (*psa_drv_entropy_init_t)(void *p_context);
/** \brief Get a specified number of bits from the entropy source
* It retrives `buffer_size` bytes of data from the entropy source. The entropy
* source will always fill the provided buffer to its full size, however, most
* entropy sources have biases, and the actual amount of entropy contained in
* the buffer will be less than the number of bytes.
* The driver will return the actual number of bytes of entropy placed in the
* buffer in `p_received_entropy_bytes`.
* A PSA Crypto API implementation will likely feed the output of this function
* into a Digital Random Bit Generator (DRBG), and typically has a minimum
* amount of entropy that it needs.
* To accomplish this, the PSA Crypto implementation should be designed to call
* this function multiple times until it has received the required amount of
* entropy from the entropy source.
* \param[in,out] p_context A hardware-specific structure
* containing any context information
* for the implementation
* \param[out] p_buffer A caller-allocated buffer for the
* retrieved entropy to be placed in
* \param[in] buffer_size The allocated size of `p_buffer`
* \param[out] p_received_entropy_bits The amount of entropy (in bits)
* actually provided in `p_buffer`
* \retval #PSA_SUCCESS
typedef psa_status_t (*psa_drv_entropy_get_bits_t)(void *p_context,
uint8_t *p_buffer,
uint32_t buffer_size,
uint32_t *p_received_entropy_bits);
* \brief A struct containing all of the function pointers needed to interface
* to an entropy source
* PSA Crypto API implementations should populate instances of the table as
* appropriate upon startup.
* If one of the functions is not implemented, it should be set to NULL.
typedef struct {
/** The driver-specific size of the entropy context */
const size_t context_size;
/** Function that performs initialization for the entropy source */
psa_drv_entropy_init_t p_init;
/** Function that performs the get_bits operation for the entropy source */
psa_drv_entropy_get_bits_t p_get_bits;
} psa_drv_entropy_t;
#ifdef __cplusplus