1 | /**
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2 | * \file chachapoly.h
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3 | *
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4 | * \brief This file contains the AEAD-ChaCha20-Poly1305 definitions and
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5 | * functions.
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6 | *
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7 | * ChaCha20-Poly1305 is an algorithm for Authenticated Encryption
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8 | * with Associated Data (AEAD) that can be used to encrypt and
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9 | * authenticate data. It is based on ChaCha20 and Poly1305 by Daniel
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10 | * Bernstein and was standardized in RFC 7539.
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11 | *
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12 | * \author Daniel King <damaki.gh@gmail.com>
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13 | */
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14 |
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15 | /* Copyright (C) 2006-2018, Arm Limited (or its affiliates), All Rights Reserved.
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16 | * SPDX-License-Identifier: Apache-2.0
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17 | *
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18 | * Licensed under the Apache License, Version 2.0 (the "License"); you may
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19 | * not use this file except in compliance with the License.
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20 | * You may obtain a copy of the License at
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21 | *
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22 | * http://www.apache.org/licenses/LICENSE-2.0
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23 | *
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24 | * Unless required by applicable law or agreed to in writing, software
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25 | * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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26 | * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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27 | * See the License for the specific language governing permissions and
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28 | * limitations under the License.
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29 | *
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30 | * This file is part of Mbed TLS (https://tls.mbed.org)
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31 | */
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32 |
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33 | #ifndef MBEDTLS_CHACHAPOLY_H
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34 | #define MBEDTLS_CHACHAPOLY_H
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35 |
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36 | #if !defined(MBEDTLS_CONFIG_FILE)
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37 | #include "config.h"
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38 | #else
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39 | #include MBEDTLS_CONFIG_FILE
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40 | #endif
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41 |
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42 | /* for shared error codes */
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43 | #include "poly1305.h"
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44 |
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45 | #define MBEDTLS_ERR_CHACHAPOLY_BAD_STATE -0x0054 /**< The requested operation is not permitted in the current state. */
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46 | #define MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED -0x0056 /**< Authenticated decryption failed: data was not authentic. */
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47 |
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48 | #ifdef __cplusplus
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49 | extern "C" {
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50 | #endif
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51 |
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52 | typedef enum
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53 | {
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54 | MBEDTLS_CHACHAPOLY_ENCRYPT, /**< The mode value for performing encryption. */
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55 | MBEDTLS_CHACHAPOLY_DECRYPT /**< The mode value for performing decryption. */
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56 | }
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57 | mbedtls_chachapoly_mode_t;
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58 |
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59 | #if !defined(MBEDTLS_CHACHAPOLY_ALT)
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60 |
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61 | #include "chacha20.h"
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62 |
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63 | typedef struct mbedtls_chachapoly_context
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64 | {
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65 | mbedtls_chacha20_context chacha20_ctx; /**< The ChaCha20 context. */
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66 | mbedtls_poly1305_context poly1305_ctx; /**< The Poly1305 context. */
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67 | uint64_t aad_len; /**< The length (bytes) of the Additional Authenticated Data. */
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68 | uint64_t ciphertext_len; /**< The length (bytes) of the ciphertext. */
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69 | int state; /**< The current state of the context. */
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70 | mbedtls_chachapoly_mode_t mode; /**< Cipher mode (encrypt or decrypt). */
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71 | }
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72 | mbedtls_chachapoly_context;
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73 |
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74 | #else /* !MBEDTLS_CHACHAPOLY_ALT */
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75 | #include "chachapoly_alt.h"
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76 | #endif /* !MBEDTLS_CHACHAPOLY_ALT */
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77 |
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78 | /**
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79 | * \brief This function initializes the specified ChaCha20-Poly1305 context.
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80 | *
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81 | * It must be the first API called before using
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82 | * the context. It must be followed by a call to
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83 | * \c mbedtls_chachapoly_setkey() before any operation can be
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84 | * done, and to \c mbedtls_chachapoly_free() once all
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85 | * operations with that context have been finished.
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86 | *
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87 | * In order to encrypt or decrypt full messages at once, for
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88 | * each message you should make a single call to
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89 | * \c mbedtls_chachapoly_crypt_and_tag() or
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90 | * \c mbedtls_chachapoly_auth_decrypt().
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91 | *
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92 | * In order to encrypt messages piecewise, for each
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93 | * message you should make a call to
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94 | * \c mbedtls_chachapoly_starts(), then 0 or more calls to
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95 | * \c mbedtls_chachapoly_update_aad(), then 0 or more calls to
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96 | * \c mbedtls_chachapoly_update(), then one call to
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97 | * \c mbedtls_chachapoly_finish().
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98 | *
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99 | * \warning Decryption with the piecewise API is discouraged! Always
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100 | * use \c mbedtls_chachapoly_auth_decrypt() when possible!
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101 | *
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102 | * If however this is not possible because the data is too
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103 | * large to fit in memory, you need to:
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104 | *
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105 | * - call \c mbedtls_chachapoly_starts() and (if needed)
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106 | * \c mbedtls_chachapoly_update_aad() as above,
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107 | * - call \c mbedtls_chachapoly_update() multiple times and
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108 | * ensure its output (the plaintext) is NOT used in any other
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109 | * way than placing it in temporary storage at this point,
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110 | * - call \c mbedtls_chachapoly_finish() to compute the
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111 | * authentication tag and compared it in constant time to the
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112 | * tag received with the ciphertext.
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113 | *
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114 | * If the tags are not equal, you must immediately discard
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115 | * all previous outputs of \c mbedtls_chachapoly_update(),
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116 | * otherwise you can now safely use the plaintext.
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117 | *
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118 | * \param ctx The ChachaPoly context to initialize. Must not be \c NULL.
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119 | */
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120 | void mbedtls_chachapoly_init( mbedtls_chachapoly_context *ctx );
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121 |
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122 | /**
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123 | * \brief This function releases and clears the specified
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124 | * ChaCha20-Poly1305 context.
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125 | *
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126 | * \param ctx The ChachaPoly context to clear. This may be \c NULL, in which
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127 | * case this function is a no-op.
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128 | */
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129 | void mbedtls_chachapoly_free( mbedtls_chachapoly_context *ctx );
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130 |
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131 | /**
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132 | * \brief This function sets the ChaCha20-Poly1305
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133 | * symmetric encryption key.
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134 | *
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135 | * \param ctx The ChaCha20-Poly1305 context to which the key should be
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136 | * bound. This must be initialized.
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137 | * \param key The \c 256 Bit (\c 32 Bytes) key.
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138 | *
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139 | * \return \c 0 on success.
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140 | * \return A negative error code on failure.
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141 | */
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142 | int mbedtls_chachapoly_setkey( mbedtls_chachapoly_context *ctx,
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143 | const unsigned char key[32] );
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144 |
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145 | /**
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146 | * \brief This function starts a ChaCha20-Poly1305 encryption or
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147 | * decryption operation.
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148 | *
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149 | * \warning You must never use the same nonce twice with the same key.
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150 | * This would void any confidentiality and authenticity
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151 | * guarantees for the messages encrypted with the same nonce
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152 | * and key.
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153 | *
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154 | * \note If the context is being used for AAD only (no data to
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155 | * encrypt or decrypt) then \p mode can be set to any value.
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156 | *
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157 | * \warning Decryption with the piecewise API is discouraged, see the
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158 | * warning on \c mbedtls_chachapoly_init().
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159 | *
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160 | * \param ctx The ChaCha20-Poly1305 context. This must be initialized
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161 | * and bound to a key.
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162 | * \param nonce The nonce/IV to use for the message.
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163 | * This must be a redable buffer of length \c 12 Bytes.
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164 | * \param mode The operation to perform: #MBEDTLS_CHACHAPOLY_ENCRYPT or
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165 | * #MBEDTLS_CHACHAPOLY_DECRYPT (discouraged, see warning).
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166 | *
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167 | * \return \c 0 on success.
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168 | * \return A negative error code on failure.
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169 | */
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170 | int mbedtls_chachapoly_starts( mbedtls_chachapoly_context *ctx,
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171 | const unsigned char nonce[12],
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172 | mbedtls_chachapoly_mode_t mode );
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173 |
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174 | /**
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175 | * \brief This function feeds additional data to be authenticated
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176 | * into an ongoing ChaCha20-Poly1305 operation.
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177 | *
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178 | * The Additional Authenticated Data (AAD), also called
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179 | * Associated Data (AD) is only authenticated but not
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180 | * encrypted nor included in the encrypted output. It is
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181 | * usually transmitted separately from the ciphertext or
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182 | * computed locally by each party.
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183 | *
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184 | * \note This function is called before data is encrypted/decrypted.
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185 | * I.e. call this function to process the AAD before calling
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186 | * \c mbedtls_chachapoly_update().
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187 | *
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188 | * You may call this function multiple times to process
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189 | * an arbitrary amount of AAD. It is permitted to call
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190 | * this function 0 times, if no AAD is used.
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191 | *
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192 | * This function cannot be called any more if data has
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193 | * been processed by \c mbedtls_chachapoly_update(),
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194 | * or if the context has been finished.
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195 | *
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196 | * \warning Decryption with the piecewise API is discouraged, see the
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197 | * warning on \c mbedtls_chachapoly_init().
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198 | *
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199 | * \param ctx The ChaCha20-Poly1305 context. This must be initialized
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200 | * and bound to a key.
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201 | * \param aad_len The length in Bytes of the AAD. The length has no
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202 | * restrictions.
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203 | * \param aad Buffer containing the AAD.
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204 | * This pointer can be \c NULL if `aad_len == 0`.
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205 | *
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206 | * \return \c 0 on success.
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207 | * \return #MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA
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208 | * if \p ctx or \p aad are NULL.
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209 | * \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE
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210 | * if the operations has not been started or has been
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211 | * finished, or if the AAD has been finished.
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212 | */
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213 | int mbedtls_chachapoly_update_aad( mbedtls_chachapoly_context *ctx,
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214 | const unsigned char *aad,
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215 | size_t aad_len );
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216 |
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217 | /**
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218 | * \brief Thus function feeds data to be encrypted or decrypted
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219 | * into an on-going ChaCha20-Poly1305
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220 | * operation.
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221 | *
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222 | * The direction (encryption or decryption) depends on the
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223 | * mode that was given when calling
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224 | * \c mbedtls_chachapoly_starts().
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225 | *
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226 | * You may call this function multiple times to process
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227 | * an arbitrary amount of data. It is permitted to call
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228 | * this function 0 times, if no data is to be encrypted
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229 | * or decrypted.
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230 | *
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231 | * \warning Decryption with the piecewise API is discouraged, see the
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232 | * warning on \c mbedtls_chachapoly_init().
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233 | *
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234 | * \param ctx The ChaCha20-Poly1305 context to use. This must be initialized.
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235 | * \param len The length (in bytes) of the data to encrypt or decrypt.
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236 | * \param input The buffer containing the data to encrypt or decrypt.
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237 | * This pointer can be \c NULL if `len == 0`.
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238 | * \param output The buffer to where the encrypted or decrypted data is
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239 | * written. This must be able to hold \p len bytes.
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240 | * This pointer can be \c NULL if `len == 0`.
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241 | *
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242 | * \return \c 0 on success.
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243 | * \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE
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244 | * if the operation has not been started or has been
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245 | * finished.
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246 | * \return Another negative error code on other kinds of failure.
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247 | */
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248 | int mbedtls_chachapoly_update( mbedtls_chachapoly_context *ctx,
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249 | size_t len,
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250 | const unsigned char *input,
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251 | unsigned char *output );
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252 |
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253 | /**
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254 | * \brief This function finished the ChaCha20-Poly1305 operation and
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255 | * generates the MAC (authentication tag).
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256 | *
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257 | * \param ctx The ChaCha20-Poly1305 context to use. This must be initialized.
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258 | * \param mac The buffer to where the 128-bit (16 bytes) MAC is written.
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259 | *
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260 | * \warning Decryption with the piecewise API is discouraged, see the
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261 | * warning on \c mbedtls_chachapoly_init().
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262 | *
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263 | * \return \c 0 on success.
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264 | * \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE
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265 | * if the operation has not been started or has been
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266 | * finished.
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267 | * \return Another negative error code on other kinds of failure.
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268 | */
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269 | int mbedtls_chachapoly_finish( mbedtls_chachapoly_context *ctx,
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270 | unsigned char mac[16] );
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271 |
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272 | /**
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273 | * \brief This function performs a complete ChaCha20-Poly1305
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274 | * authenticated encryption with the previously-set key.
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275 | *
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276 | * \note Before using this function, you must set the key with
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277 | * \c mbedtls_chachapoly_setkey().
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278 | *
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279 | * \warning You must never use the same nonce twice with the same key.
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280 | * This would void any confidentiality and authenticity
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281 | * guarantees for the messages encrypted with the same nonce
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282 | * and key.
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283 | *
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284 | * \param ctx The ChaCha20-Poly1305 context to use (holds the key).
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285 | * This must be initialized.
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286 | * \param length The length (in bytes) of the data to encrypt or decrypt.
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287 | * \param nonce The 96-bit (12 bytes) nonce/IV to use.
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288 | * \param aad The buffer containing the additional authenticated
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289 | * data (AAD). This pointer can be \c NULL if `aad_len == 0`.
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290 | * \param aad_len The length (in bytes) of the AAD data to process.
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291 | * \param input The buffer containing the data to encrypt or decrypt.
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292 | * This pointer can be \c NULL if `ilen == 0`.
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293 | * \param output The buffer to where the encrypted or decrypted data
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294 | * is written. This pointer can be \c NULL if `ilen == 0`.
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295 | * \param tag The buffer to where the computed 128-bit (16 bytes) MAC
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296 | * is written. This must not be \c NULL.
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297 | *
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298 | * \return \c 0 on success.
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299 | * \return A negative error code on failure.
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300 | */
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301 | int mbedtls_chachapoly_encrypt_and_tag( mbedtls_chachapoly_context *ctx,
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302 | size_t length,
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303 | const unsigned char nonce[12],
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304 | const unsigned char *aad,
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305 | size_t aad_len,
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306 | const unsigned char *input,
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307 | unsigned char *output,
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308 | unsigned char tag[16] );
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309 |
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310 | /**
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311 | * \brief This function performs a complete ChaCha20-Poly1305
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312 | * authenticated decryption with the previously-set key.
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313 | *
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314 | * \note Before using this function, you must set the key with
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315 | * \c mbedtls_chachapoly_setkey().
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316 | *
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317 | * \param ctx The ChaCha20-Poly1305 context to use (holds the key).
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318 | * \param length The length (in Bytes) of the data to decrypt.
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319 | * \param nonce The \c 96 Bit (\c 12 bytes) nonce/IV to use.
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320 | * \param aad The buffer containing the additional authenticated data (AAD).
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321 | * This pointer can be \c NULL if `aad_len == 0`.
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322 | * \param aad_len The length (in bytes) of the AAD data to process.
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323 | * \param tag The buffer holding the authentication tag.
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324 | * This must be a readable buffer of length \c 16 Bytes.
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325 | * \param input The buffer containing the data to decrypt.
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326 | * This pointer can be \c NULL if `ilen == 0`.
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327 | * \param output The buffer to where the decrypted data is written.
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328 | * This pointer can be \c NULL if `ilen == 0`.
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329 | *
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330 | * \return \c 0 on success.
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331 | * \return #MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED
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332 | * if the data was not authentic.
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333 | * \return Another negative error code on other kinds of failure.
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334 | */
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335 | int mbedtls_chachapoly_auth_decrypt( mbedtls_chachapoly_context *ctx,
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336 | size_t length,
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337 | const unsigned char nonce[12],
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338 | const unsigned char *aad,
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339 | size_t aad_len,
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340 | const unsigned char tag[16],
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341 | const unsigned char *input,
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342 | unsigned char *output );
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343 |
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344 | #if defined(MBEDTLS_SELF_TEST)
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345 | /**
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346 | * \brief The ChaCha20-Poly1305 checkup routine.
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347 | *
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348 | * \return \c 0 on success.
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349 | * \return \c 1 on failure.
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350 | */
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351 | int mbedtls_chachapoly_self_test( int verbose );
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352 | #endif /* MBEDTLS_SELF_TEST */
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353 |
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354 | #ifdef __cplusplus
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355 | }
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356 | #endif
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357 |
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358 | #endif /* MBEDTLS_CHACHAPOLY_H */
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