| 1 | /** |
| 2 | * \file ctr.h |
| 3 | * |
| 4 | * \brief This file contains common functionality for counter algorithms. |
| 5 | * |
| 6 | * Copyright The Mbed TLS Contributors |
| 7 | * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later |
| 8 | */ |
| 9 | |
| 10 | #ifndef MBEDTLS_CTR_H |
| 11 | #define MBEDTLS_CTR_H |
| 12 | |
| 13 | #include "common.h" |
| 14 | |
| 15 | /** |
| 16 | * \brief Increment a big-endian 16-byte value. |
| 17 | * This is quite performance-sensitive for AES-CTR and CTR-DRBG. |
| 18 | * |
| 19 | * \param n A 16-byte value to be incremented. |
| 20 | */ |
| 21 | static inline void mbedtls_ctr_increment_counter(uint8_t n[16]) |
| 22 | { |
| 23 | // The 32-bit version seems to perform about the same as a 64-bit version |
| 24 | // on 64-bit architectures, so no need to define a 64-bit version. |
| 25 | for (int i = 3;; i--) { |
| 26 | uint32_t x = MBEDTLS_GET_UINT32_BE(n, i << 2); |
| 27 | x += 1; |
| 28 | MBEDTLS_PUT_UINT32_BE(x, n, i << 2); |
| 29 | if (x != 0 || i == 0) { |
| 30 | break; |
| 31 | } |
| 32 | } |
| 33 | } |
| 34 | |
| 35 | #endif /* MBEDTLS_CTR_H */ |
| 36 | |