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36 lines
947 B
C
36 lines
947 B
C
/**
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* \file ctr.h
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*
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* \brief This file contains common functionality for counter algorithms.
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*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
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*/
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#ifndef MBEDTLS_CTR_H
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#define MBEDTLS_CTR_H
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#include "common.h"
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/**
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* \brief Increment a big-endian 16-byte value.
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* This is quite performance-sensitive for AES-CTR and CTR-DRBG.
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*
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* \param n A 16-byte value to be incremented.
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*/
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static inline void mbedtls_ctr_increment_counter(uint8_t n[16])
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{
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// The 32-bit version seems to perform about the same as a 64-bit version
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// on 64-bit architectures, so no need to define a 64-bit version.
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for (int i = 3;; i--) {
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uint32_t x = MBEDTLS_GET_UINT32_BE(n, i << 2);
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x += 1;
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MBEDTLS_PUT_UINT32_BE(x, n, i << 2);
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if (x != 0 || i == 0) {
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break;
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}
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}
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}
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#endif /* MBEDTLS_CTR_H */
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