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Introduce mbedtls_ctr_increment_counter

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
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Dave Rodgman 2024-01-13 16:40:58 +00:00
parent c4f984f2a5
commit b49cf1019d
1 changed files with 30 additions and 0 deletions
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library/ctr.h Normal file
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/**
* \file ctr.h
*
* \brief This file contains common functionality for counter algorithms.
*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
*/
#include "common.h"
/**
* \brief Increment a big-endian 16-byte value.
* This is quite performance-sensitive for AES-CTR and CTR-DRBG.
*
* \param n A 16-byte value to be incremented.
*/
static inline void mbedtls_ctr_increment_counter(uint8_t n[16])
{
// The 32-bit version seems to perform about the same as a 64-bit version
// on 64-bit architectures, so no need to define a 64-bit version.
for (int i = 3;; i--) {
uint32_t x = MBEDTLS_GET_UINT32_BE(n, i << 2);
x += 1;
MBEDTLS_PUT_UINT32_BE(x, n, i << 2);
if (x != 0 || i == 0) {
break;
}
}
}