1 /** 2 * \file chacha20.h 3 * 4 * \brief This file contains ChaCha20 definitions and functions. 5 * 6 * ChaCha20 is a stream cipher that can encrypt and decrypt 7 * information. ChaCha was created by Daniel Bernstein as a variant of 8 * its Salsa cipher https://cr.yp.to/chacha/chacha-20080128.pdf 9 * ChaCha20 is the variant with 20 rounds, that was also standardized 10 * in RFC 7539. 11 * 12 * \author Daniel King <damaki.gh@gmail.com> 13 */ 14 15 /* 16 * Copyright The Mbed TLS Contributors 17 * SPDX-License-Identifier: Apache-2.0 18 * 19 * Licensed under the Apache License, Version 2.0 (the "License"); you may 20 * not use this file except in compliance with the License. 21 * You may obtain a copy of the License at 22 * 23 * http://www.apache.org/licenses/LICENSE-2.0 24 * 25 * Unless required by applicable law or agreed to in writing, software 26 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 27 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 28 * See the License for the specific language governing permissions and 29 * limitations under the License. 30 */ 31 32 #ifndef MBEDTLS_CHACHA20_H 33 #define MBEDTLS_CHACHA20_H 34 35 #if !defined(MBEDTLS_CONFIG_FILE) 36 #include "mbedtls/config.h" 37 #else 38 #include MBEDTLS_CONFIG_FILE 39 #endif 40 41 #include <stdint.h> 42 #include <stddef.h> 43 44 #define MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA -0x0051 /**< Invalid input parameter(s). */ 45 46 /* MBEDTLS_ERR_CHACHA20_FEATURE_UNAVAILABLE is deprecated and should not be 47 * used. */ 48 #define MBEDTLS_ERR_CHACHA20_FEATURE_UNAVAILABLE -0x0053 /**< Feature not available. For example, s part of the API is not implemented. */ 49 50 /* MBEDTLS_ERR_CHACHA20_HW_ACCEL_FAILED is deprecated and should not be used. 51 */ 52 #define MBEDTLS_ERR_CHACHA20_HW_ACCEL_FAILED -0x0055 /**< Chacha20 hardware accelerator failed. */ 53 54 #ifdef __cplusplus 55 extern "C" { 56 #endif 57 58 #if !defined(MBEDTLS_CHACHA20_ALT) 59 60 typedef struct mbedtls_chacha20_context 61 { 62 uint32_t state[16]; /*! The state (before round operations). */ 63 uint8_t keystream8[64]; /*! Leftover keystream bytes. */ 64 size_t keystream_bytes_used; /*! Number of keystream bytes already used. */ 65 } 66 mbedtls_chacha20_context; 67 68 #else /* MBEDTLS_CHACHA20_ALT */ 69 #include "chacha20_alt.h" 70 #endif /* MBEDTLS_CHACHA20_ALT */ 71 72 /** 73 * \brief This function initializes the specified ChaCha20 context. 74 * 75 * It must be the first API called before using 76 * the context. 77 * 78 * It is usually followed by calls to 79 * \c mbedtls_chacha20_setkey() and 80 * \c mbedtls_chacha20_starts(), then one or more calls to 81 * to \c mbedtls_chacha20_update(), and finally to 82 * \c mbedtls_chacha20_free(). 83 * 84 * \param ctx The ChaCha20 context to initialize. 85 * This must not be \c NULL. 86 */ 87 void mbedtls_chacha20_init( mbedtls_chacha20_context *ctx ); 88 89 /** 90 * \brief This function releases and clears the specified 91 * ChaCha20 context. 92 * 93 * \param ctx The ChaCha20 context to clear. This may be \c NULL, 94 * in which case this function is a no-op. If it is not 95 * \c NULL, it must point to an initialized context. 96 * 97 */ 98 void mbedtls_chacha20_free( mbedtls_chacha20_context *ctx ); 99 100 /** 101 * \brief This function sets the encryption/decryption key. 102 * 103 * \note After using this function, you must also call 104 * \c mbedtls_chacha20_starts() to set a nonce before you 105 * start encrypting/decrypting data with 106 * \c mbedtls_chacha_update(). 107 * 108 * \param ctx The ChaCha20 context to which the key should be bound. 109 * It must be initialized. 110 * \param key The encryption/decryption key. This must be \c 32 Bytes 111 * in length. 112 * 113 * \return \c 0 on success. 114 * \return #MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA if ctx or key is NULL. 115 */ 116 int mbedtls_chacha20_setkey( mbedtls_chacha20_context *ctx, 117 const unsigned char key[32] ); 118 119 /** 120 * \brief This function sets the nonce and initial counter value. 121 * 122 * \note A ChaCha20 context can be re-used with the same key by 123 * calling this function to change the nonce. 124 * 125 * \warning You must never use the same nonce twice with the same key. 126 * This would void any confidentiality guarantees for the 127 * messages encrypted with the same nonce and key. 128 * 129 * \param ctx The ChaCha20 context to which the nonce should be bound. 130 * It must be initialized and bound to a key. 131 * \param nonce The nonce. This must be \c 12 Bytes in size. 132 * \param counter The initial counter value. This is usually \c 0. 133 * 134 * \return \c 0 on success. 135 * \return #MBEDTLS_ERR_CHACHA20_BAD_INPUT_DATA if ctx or nonce is 136 * NULL. 137 */ 138 int mbedtls_chacha20_starts( mbedtls_chacha20_context* ctx, 139 const unsigned char nonce[12], 140 uint32_t counter ); 141 142 /** 143 * \brief This function encrypts or decrypts data. 144 * 145 * Since ChaCha20 is a stream cipher, the same operation is 146 * used for encrypting and decrypting data. 147 * 148 * \note The \p input and \p output pointers must either be equal or 149 * point to non-overlapping buffers. 150 * 151 * \note \c mbedtls_chacha20_setkey() and 152 * \c mbedtls_chacha20_starts() must be called at least once 153 * to setup the context before this function can be called. 154 * 155 * \note This function can be called multiple times in a row in 156 * order to encrypt of decrypt data piecewise with the same 157 * key and nonce. 158 * 159 * \param ctx The ChaCha20 context to use for encryption or decryption. 160 * It must be initialized and bound to a key and nonce. 161 * \param size The length of the input data in Bytes. 162 * \param input The buffer holding the input data. 163 * This pointer can be \c NULL if `size == 0`. 164 * \param output The buffer holding the output data. 165 * This must be able to hold \p size Bytes. 166 * This pointer can be \c NULL if `size == 0`. 167 * 168 * \return \c 0 on success. 169 * \return A negative error code on failure. 170 */ 171 int mbedtls_chacha20_update( mbedtls_chacha20_context *ctx, 172 size_t size, 173 const unsigned char *input, 174 unsigned char *output ); 175 176 /** 177 * \brief This function encrypts or decrypts data with ChaCha20 and 178 * the given key and nonce. 179 * 180 * Since ChaCha20 is a stream cipher, the same operation is 181 * used for encrypting and decrypting data. 182 * 183 * \warning You must never use the same (key, nonce) pair more than 184 * once. This would void any confidentiality guarantees for 185 * the messages encrypted with the same nonce and key. 186 * 187 * \note The \p input and \p output pointers must either be equal or 188 * point to non-overlapping buffers. 189 * 190 * \param key The encryption/decryption key. 191 * This must be \c 32 Bytes in length. 192 * \param nonce The nonce. This must be \c 12 Bytes in size. 193 * \param counter The initial counter value. This is usually \c 0. 194 * \param size The length of the input data in Bytes. 195 * \param input The buffer holding the input data. 196 * This pointer can be \c NULL if `size == 0`. 197 * \param output The buffer holding the output data. 198 * This must be able to hold \p size Bytes. 199 * This pointer can be \c NULL if `size == 0`. 200 * 201 * \return \c 0 on success. 202 * \return A negative error code on failure. 203 */ 204 int mbedtls_chacha20_crypt( const unsigned char key[32], 205 const unsigned char nonce[12], 206 uint32_t counter, 207 size_t size, 208 const unsigned char* input, 209 unsigned char* output ); 210 211 #if defined(MBEDTLS_SELF_TEST) 212 /** 213 * \brief The ChaCha20 checkup routine. 214 * 215 * \return \c 0 on success. 216 * \return \c 1 on failure. 217 */ 218 int mbedtls_chacha20_self_test( int verbose ); 219 #endif /* MBEDTLS_SELF_TEST */ 220 221 #ifdef __cplusplus 222 } 223 #endif 224 225 #endif /* MBEDTLS_CHACHA20_H */ 226