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93 lines
2.2 KiB
C
93 lines
2.2 KiB
C
/*
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* Copyright (C) 2018 HAW Hamburg
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @defgroup sys_puf_sram SRAM PUF
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* @ingroup sys
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*
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* @brief SRAM based physically unclonable function (PUF)
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* @experimental
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*
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* @{
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* @file
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*
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* @author Peter Kietzmann <peter.kietzmann@haw-hamburg.de>
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*/
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#ifndef PUF_SRAM_H
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#define PUF_SRAM_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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#include "hashes.h"
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#include "thread.h"
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/**
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* @brief SRAM length considered for seeding
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*/
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#ifndef SEED_RAM_LEN
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#define SEED_RAM_LEN (2048 / sizeof(uint32_t))
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#endif
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/**
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* @brief SRAM marker to detect reboot without power-off
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*
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* Source: https://www.random.org/bytes/
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*/
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#define PUF_SRAM_MARKER (0xad3021ff)
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/**
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* @brief Global seed variable, allocated in puf_sram.c
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*/
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extern uint32_t puf_sram_seed;
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/**
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* @brief Global seed state, allocated in puf_sram.c
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* 0 means seed was generated from SRAM pattern,
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1 means missing power cycle detected,
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2 means power cycle detected. The state will most likely
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be overwritten with 0 in the next steps
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*/
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extern uint32_t puf_sram_state;
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/**
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* @brief checks source of reboot by @p puf_sram_softreset and conditionally
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calls @p puf_sram_generate
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*
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* @param[in] ram pointer to SRAM memory
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* @param[in] len length of the memroy to consider
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*
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*/
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void puf_sram_init(const uint8_t *ram, size_t len);
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/**
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* @brief builds hash from @p SEED_RAM_LEN bytes uninitialized SRAM, writes it
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* to the global variable @p puf_sram_seed and returns the value
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*
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* @param[in] ram pointer to SRAM memory
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* @param[in] len length of the memroy to consider
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*/
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void puf_sram_generate(const uint8_t *ram, size_t len);
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/**
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* @brief checks for a memory marker to determine whether memory contains old data.
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Otherwise it assumes a reboot from power down mode
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*
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* @return 0 when reset with power cycle was detected
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* @return 1 when reset without power cycle was detected
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*/
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bool puf_sram_softreset(void);
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#ifdef __cplusplus
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}
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#endif
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/** @} */
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#endif /* PUF_SRAM_H */
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