/work/toxencryptsave/toxencryptsave.h

Source
/* SPDX-License-Identifier: GPL-3.0-or-later
 * Copyright © 2016-2026 The TokTok team.
 * Copyright © 2013-2016 Tox Developers.
 */

/**
 * Batch encryption functions.
 */

#ifndef C_TOXCORE_TOXENCRYPTSAVE_TOXENCRYPTSAVE_H
#define C_TOXCORE_TOXENCRYPTSAVE_TOXENCRYPTSAVE_H

#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>

#ifdef __cplusplus
extern "C" {
#endif

/*******************************************************************************
 *
 * This module is organized into two parts.
 *
 * 1. A simple API operating on plain text/cipher text data and a password to
 *    encrypt or decrypt it.
 * 2. A more advanced API that splits key derivation and encryption into two
 *    separate function calls.
 *
 * The first part is implemented in terms of the second part and simply calls
 * the separate functions in sequence. Since key derivation is very expensive
 * compared to the actual encryption, clients that do a lot of crypto should
 * prefer the advanced API and reuse pass-key objects.
 *
 * To use the second part, first derive an encryption key from a password with
 * tox_pass_key_derive, then use the derived key to encrypt the data.
 *
 * The encrypted data is prepended with a magic number, to aid validity
 * checking (no guarantees are made of course). Any data to be decrypted must
 * start with the magic number.
 *
 * Clients should consider alerting their users that, unlike plain data, if
 * even one bit becomes corrupted, the data will be entirely unrecoverable.
 * Ditto if they forget their password, there is no way to recover the data.
 *
 ******************************************************************************/

/**
 * The size of the salt part of a pass-key.
 */
#define TOX_PASS_SALT_LENGTH           32

uint32_t tox_pass_salt_length(void);

typedef uint8_t Tox_Pass_Salt[TOX_PASS_SALT_LENGTH];

/**
 * The size of the key part of a pass-key.
 */
#define TOX_PASS_KEY_LENGTH            32

uint32_t tox_pass_key_length(void);

/**
 * The amount of additional data required to store any encrypted byte array.
 * Encrypting an array of N bytes requires N + TOX_PASS_ENCRYPTION_EXTRA_LENGTH
 * bytes in the encrypted byte array.
 */
#define TOX_PASS_ENCRYPTION_EXTRA_LENGTH 80

uint32_t tox_pass_encryption_extra_length(void);

typedef enum Tox_Err_Key_Derivation {

    /**
     * The function returned successfully.
     */
    TOX_ERR_KEY_DERIVATION_OK,

    /**
     * One of the arguments to the function was NULL when it was not expected.
     */
    TOX_ERR_KEY_DERIVATION_NULL,

    /**
     * The crypto lib was unable to derive a key from the given passphrase,
     * which is usually a lack of memory issue.
     */
    TOX_ERR_KEY_DERIVATION_FAILED,

} Tox_Err_Key_Derivation;

const char *tox_err_key_derivation_to_string(Tox_Err_Key_Derivation error);

typedef enum Tox_Err_Encryption {

    /**
     * The function returned successfully.
     */
    TOX_ERR_ENCRYPTION_OK,

    /**
     * One of the arguments to the function was NULL when it was not expected.
     */
    TOX_ERR_ENCRYPTION_NULL,

    /**
     * The crypto lib was unable to derive a key from the given passphrase,
     * which is usually a lack of memory issue. The functions accepting keys
     * do not produce this error.
     */
    TOX_ERR_ENCRYPTION_KEY_DERIVATION_FAILED,

    /**
     * The encryption itself failed.
     */
    TOX_ERR_ENCRYPTION_FAILED,

} Tox_Err_Encryption;

const char *tox_err_encryption_to_string(Tox_Err_Encryption error);

typedef enum Tox_Err_Decryption {

    /**
     * The function returned successfully.
     */
    TOX_ERR_DECRYPTION_OK,

    /**
     * One of the arguments to the function was NULL when it was not expected.
     */
    TOX_ERR_DECRYPTION_NULL,

    /**
     * The input data was shorter than TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes
     */
    TOX_ERR_DECRYPTION_INVALID_LENGTH,

    /**
     * The input data is missing the magic number (i.e. wasn't created by this
     * module, or is corrupted).
     */
    TOX_ERR_DECRYPTION_BAD_FORMAT,

    /**
     * The crypto lib was unable to derive a key from the given passphrase,
     * which is usually a lack of memory issue. The functions accepting keys
     * do not produce this error.
     */
    TOX_ERR_DECRYPTION_KEY_DERIVATION_FAILED,

    /**
     * The encrypted byte array could not be decrypted. Either the data was
     * corrupted or the password/key was incorrect.
     */
    TOX_ERR_DECRYPTION_FAILED,

} Tox_Err_Decryption;

const char *tox_err_decryption_to_string(Tox_Err_Decryption error);

/*******************************************************************************
 *
 *                                BEGIN PART 1
 *
 * The simple API is presented first. If your code spends too much time using
 * these functions, consider using the advanced functions instead and caching
 * the generated pass-key.
 *
 ******************************************************************************/

/**
 * Encrypts the given data with the given passphrase.
 *
 * The output array must be at least
 * `plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH` bytes long. This delegates
 * to tox_pass_key_derive and tox_pass_key_encrypt.
 *
 * @param plaintext A byte array of length `plaintext_len`.
 * @param plaintext_len The length of the plain text array. Bigger than 0.
 * @param passphrase The user-provided password. Can be empty.
 * @param passphrase_len The length of the password.
 * @param ciphertext The cipher text array to write the encrypted data to.
 *
 * @return true on success.
 */
bool tox_pass_encrypt(const uint8_t plaintext[], size_t plaintext_len, const uint8_t passphrase[], size_t passphrase_len,
                      uint8_t ciphertext[/*! plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH */], Tox_Err_Encryption *error);

/**
 * Decrypts the given data with the given passphrase.
 *
 * The output array must be at least
 * `ciphertext_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH` bytes long. This
 * delegates to tox_pass_key_decrypt.
 *
 * @param ciphertext A byte array of length `ciphertext_len`.
 * @param ciphertext_len The length of the cipher text array. At least
 *   TOX_PASS_ENCRYPTION_EXTRA_LENGTH.
 * @param passphrase The user-provided password. Can be empty.
 * @param passphrase_len The length of the password.
 * @param plaintext The plain text array to write the decrypted data to.
 *
 * @return true on success.
 */
bool tox_pass_decrypt(const uint8_t ciphertext[], size_t ciphertext_len, const uint8_t passphrase[],
                      size_t passphrase_len, uint8_t plaintext[/*! ciphertext_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH */], Tox_Err_Decryption *error);

/*******************************************************************************
 *
 *                                BEGIN PART 2
 *
 * And now part 2, which does the actual encryption, and can be used to write
 * less CPU intensive client code than part one.
 *
 ******************************************************************************/

/**
 * This type represents a pass-key.
 *
 * A pass-key and a password are two different concepts: a password is given
 * by the user in plain text. A pass-key is the generated symmetric key used
 * for encryption and decryption. It is derived from a salt and the
 * user-provided password.
 *
 * The Tox_Pass_Key structure is hidden in the implementation. It can be created
 * using tox_pass_key_derive or tox_pass_key_derive_with_salt and must be
 * deallocated using tox_pass_key_free.
 */
typedef struct Tox_Pass_Key Tox_Pass_Key;

/**
 * Deallocate a Tox_Pass_Key. This function behaves like `free()`, so NULL is an
 * acceptable argument value.
 */
void tox_pass_key_free(Tox_Pass_Key *key);

/**
 * Generates a secret symmetric key from the given passphrase.
 *
 * Be sure to not compromise the key! Only keep it in memory, do not write
 * it to disk.
 *
 * Note that this function is not deterministic; to derive the same key from
 * a password, you also must know the random salt that was used. A
 * deterministic version of this function is `tox_pass_key_derive_with_salt`.
 *
 * @param passphrase The user-provided password. Can be empty.
 * @param passphrase_len The length of the password.
 *
 * @return new symmetric key on success, NULL on failure.
 */
Tox_Pass_Key *tox_pass_key_derive(
    const uint8_t passphrase[], size_t passphrase_len,
    Tox_Err_Key_Derivation *error);

/**
 * Same as above, except use the given salt for deterministic key derivation.
 *
 * @param passphrase The user-provided password. Can be empty.
 * @param passphrase_len The length of the password.
 * @param salt An array of exactly TOX_PASS_SALT_LENGTH bytes.
 *
 * @return new symmetric key on success, NULL on failure.
 */
Tox_Pass_Key *tox_pass_key_derive_with_salt(
    const uint8_t passphrase[], size_t passphrase_len,
    const Tox_Pass_Salt salt, Tox_Err_Key_Derivation *error);

/**
 * Encrypt a plain text with a key produced by tox_pass_key_derive or
 * tox_pass_key_derive_with_salt.
 *
 * The output array must be at least
 * `plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH` bytes long.
 *
 * @param plaintext A byte array of length `plaintext_len`.
 * @param plaintext_len The length of the plain text array. Bigger than 0.
 * @param ciphertext The cipher text array to write the encrypted data to.
 *
 * @return true on success.
 */
bool tox_pass_key_encrypt(const Tox_Pass_Key *key, const uint8_t plaintext[], size_t plaintext_len,
                          uint8_t ciphertext[/*! plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH */], Tox_Err_Encryption *error);

/**
 * This is the inverse of tox_pass_key_encrypt, also using only keys produced by
 * tox_pass_key_derive or tox_pass_key_derive_with_salt.
 *
 * @param ciphertext A byte array of length `ciphertext_len`.
 * @param ciphertext_len The length of the cipher text array. At least
 *   TOX_PASS_ENCRYPTION_EXTRA_LENGTH.
 * @param plaintext The plain text array to write the decrypted data to.
 *
 * @return true on success.
 */
bool tox_pass_key_decrypt(const Tox_Pass_Key *key, const uint8_t ciphertext[], size_t ciphertext_len,
                          uint8_t plaintext[/*! ciphertext_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH */], Tox_Err_Decryption *error);

typedef enum Tox_Err_Get_Salt {

    /**
     * The function returned successfully.
     */
    TOX_ERR_GET_SALT_OK,

    /**
     * One of the arguments to the function was NULL when it was not expected.
     */
    TOX_ERR_GET_SALT_NULL,

    /**
     * The input data is missing the magic number (i.e. wasn't created by this
     * module, or is corrupted).
     */
    TOX_ERR_GET_SALT_BAD_FORMAT,

} Tox_Err_Get_Salt;

const char *tox_err_get_salt_to_string(Tox_Err_Get_Salt error);

/**
 * Retrieves the salt used to encrypt the given data.
 *
 * The retrieved salt can then be passed to tox_pass_key_derive_with_salt to
 * produce the same key as was previously used. Any data encrypted with this
 * module can be used as input.
 *
 * The cipher text must be at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes in
 * length.
 * The salt must be TOX_PASS_SALT_LENGTH bytes in length.
 * If the passed byte arrays are smaller than required, the behaviour is
 * undefined.
 *
 * If the cipher text pointer or the salt is NULL, this function returns false.
 *
 * Success does not say anything about the validity of the data, only that
 * data of the appropriate size was copied.
 *
 * @param ciphertext The encrypted data; at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes are read.
 * @param salt An array of exactly TOX_PASS_SALT_LENGTH bytes to write the salt to.
 *
 * @return true on success.
 */
bool tox_get_salt(
    const uint8_t ciphertext[TOX_PASS_ENCRYPTION_EXTRA_LENGTH],
    Tox_Pass_Salt salt, Tox_Err_Get_Salt *error);

/**
 * Determines whether or not the given data is encrypted by this module.
 *
 * It does this check by verifying that the magic number is the one put in
 * place by the encryption functions.
 *
 * The data must be at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes in length.
 * If the passed byte array is smaller than required, the behaviour is
 * undefined.
 *
 * If the data pointer is NULL, the behaviour is undefined
 *
 * @param data The data to check; at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes are read.
 *
 * @return true if the data is encrypted by this module.
 */
bool tox_is_data_encrypted(const uint8_t data[TOX_PASS_ENCRYPTION_EXTRA_LENGTH]);

#ifdef __cplusplus
} /* extern "C" */
#endif

//!TOKSTYLE-

typedef Tox_Err_Key_Derivation TOX_ERR_KEY_DERIVATION;
typedef Tox_Err_Encryption TOX_ERR_ENCRYPTION;
typedef Tox_Err_Decryption TOX_ERR_DECRYPTION;
typedef Tox_Err_Get_Salt TOX_ERR_GET_SALT;

//!TOKSTYLE+

#endif /* C_TOXCORE_TOXENCRYPTSAVE_TOXENCRYPTSAVE_H */

Coverage Report

Created: 2026-10-24 08:16

Line	Count	Source
1		/* SPDX-License-Identifier: GPL-3.0-or-later
2		* Copyright © 2016-2026 The TokTok team.
3		* Copyright © 2013-2016 Tox Developers.
4		*/
5
6		/**
7		* Batch encryption functions.
8		*/
9
10		#ifndef C_TOXCORE_TOXENCRYPTSAVE_TOXENCRYPTSAVE_H
11		#define C_TOXCORE_TOXENCRYPTSAVE_TOXENCRYPTSAVE_H
12
13		#include <stdbool.h>
14		#include <stddef.h>
15		#include <stdint.h>
16
17		#ifdef __cplusplus
18		extern "C" {
19		#endif
20
21		/*******************************************************************************
22		*
23		* This module is organized into two parts.
24		*
25		* 1. A simple API operating on plain text/cipher text data and a password to
26		* encrypt or decrypt it.
27		* 2. A more advanced API that splits key derivation and encryption into two
28		* separate function calls.
29		*
30		* The first part is implemented in terms of the second part and simply calls
31		* the separate functions in sequence. Since key derivation is very expensive
32		* compared to the actual encryption, clients that do a lot of crypto should
33		* prefer the advanced API and reuse pass-key objects.
34		*
35		* To use the second part, first derive an encryption key from a password with
36		* tox_pass_key_derive, then use the derived key to encrypt the data.
37		*
38		* The encrypted data is prepended with a magic number, to aid validity
39		* checking (no guarantees are made of course). Any data to be decrypted must
40		* start with the magic number.
41		*
42		* Clients should consider alerting their users that, unlike plain data, if
43		* even one bit becomes corrupted, the data will be entirely unrecoverable.
44		* Ditto if they forget their password, there is no way to recover the data.
45		*
46		******************************************************************************/
47
48		/**
49		* The size of the salt part of a pass-key.
50		*/
51	15	#define TOX_PASS_SALT_LENGTH 32
52
53		uint32_t tox_pass_salt_length(void);
54
55		typedef uint8_t Tox_Pass_Salt[TOX_PASS_SALT_LENGTH];
56
57		/**
58		* The size of the key part of a pass-key.
59		*/
60	14	#define TOX_PASS_KEY_LENGTH 32
61
62		uint32_t tox_pass_key_length(void);
63
64		/**
65		* The amount of additional data required to store any encrypted byte array.
66		* Encrypting an array of N bytes requires N + TOX_PASS_ENCRYPTION_EXTRA_LENGTH
67		* bytes in the encrypted byte array.
68		*/
69	32	#define TOX_PASS_ENCRYPTION_EXTRA_LENGTH 80
70
71		uint32_t tox_pass_encryption_extra_length(void);
72
73		typedef enum Tox_Err_Key_Derivation {
74
75		/**
76		* The function returned successfully.
77		*/
78		TOX_ERR_KEY_DERIVATION_OK,
79
80		/**
81		* One of the arguments to the function was NULL when it was not expected.
82		*/
83		TOX_ERR_KEY_DERIVATION_NULL,
84
85		/**
86		* The crypto lib was unable to derive a key from the given passphrase,
87		* which is usually a lack of memory issue.
88		*/
89		TOX_ERR_KEY_DERIVATION_FAILED,
90
91		} Tox_Err_Key_Derivation;
92
93		const char *tox_err_key_derivation_to_string(Tox_Err_Key_Derivation error);
94
95		typedef enum Tox_Err_Encryption {
96
97		/**
98		* The function returned successfully.
99		*/
100		TOX_ERR_ENCRYPTION_OK,
101
102		/**
103		* One of the arguments to the function was NULL when it was not expected.
104		*/
105		TOX_ERR_ENCRYPTION_NULL,
106
107		/**
108		* The crypto lib was unable to derive a key from the given passphrase,
109		* which is usually a lack of memory issue. The functions accepting keys
110		* do not produce this error.
111		*/
112		TOX_ERR_ENCRYPTION_KEY_DERIVATION_FAILED,
113
114		/**
115		* The encryption itself failed.
116		*/
117		TOX_ERR_ENCRYPTION_FAILED,
118
119		} Tox_Err_Encryption;
120
121		const char *tox_err_encryption_to_string(Tox_Err_Encryption error);
122
123		typedef enum Tox_Err_Decryption {
124
125		/**
126		* The function returned successfully.
127		*/
128		TOX_ERR_DECRYPTION_OK,
129
130		/**
131		* One of the arguments to the function was NULL when it was not expected.
132		*/
133		TOX_ERR_DECRYPTION_NULL,
134
135		/**
136		* The input data was shorter than TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes
137		*/
138		TOX_ERR_DECRYPTION_INVALID_LENGTH,
139
140		/**
141		* The input data is missing the magic number (i.e. wasn't created by this
142		* module, or is corrupted).
143		*/
144		TOX_ERR_DECRYPTION_BAD_FORMAT,
145
146		/**
147		* The crypto lib was unable to derive a key from the given passphrase,
148		* which is usually a lack of memory issue. The functions accepting keys
149		* do not produce this error.
150		*/
151		TOX_ERR_DECRYPTION_KEY_DERIVATION_FAILED,
152
153		/**
154		* The encrypted byte array could not be decrypted. Either the data was
155		* corrupted or the password/key was incorrect.
156		*/
157		TOX_ERR_DECRYPTION_FAILED,
158
159		} Tox_Err_Decryption;
160
161		const char *tox_err_decryption_to_string(Tox_Err_Decryption error);
162
163		/*******************************************************************************
164		*
165		* BEGIN PART 1
166		*
167		* The simple API is presented first. If your code spends too much time using
168		* these functions, consider using the advanced functions instead and caching
169		* the generated pass-key.
170		*
171		******************************************************************************/
172
173		/**
174		* Encrypts the given data with the given passphrase.
175		*
176		* The output array must be at least
177		* `plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH` bytes long. This delegates
178		* to tox_pass_key_derive and tox_pass_key_encrypt.
179		*
180		* @param plaintext A byte array of length `plaintext_len`.
181		* @param plaintext_len The length of the plain text array. Bigger than 0.
182		* @param passphrase The user-provided password. Can be empty.
183		* @param passphrase_len The length of the password.
184		* @param ciphertext The cipher text array to write the encrypted data to.
185		*
186		* @return true on success.
187		*/
188		bool tox_pass_encrypt(const uint8_t plaintext[], size_t plaintext_len, const uint8_t passphrase[], size_t passphrase_len,
189		uint8_t ciphertext[/! plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH /], Tox_Err_Encryption *error);
190
191		/**
192		* Decrypts the given data with the given passphrase.
193		*
194		* The output array must be at least
195		* `ciphertext_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH` bytes long. This
196		* delegates to tox_pass_key_decrypt.
197		*
198		* @param ciphertext A byte array of length `ciphertext_len`.
199		* @param ciphertext_len The length of the cipher text array. At least
200		* TOX_PASS_ENCRYPTION_EXTRA_LENGTH.
201		* @param passphrase The user-provided password. Can be empty.
202		* @param passphrase_len The length of the password.
203		* @param plaintext The plain text array to write the decrypted data to.
204		*
205		* @return true on success.
206		*/
207		bool tox_pass_decrypt(const uint8_t ciphertext[], size_t ciphertext_len, const uint8_t passphrase[],
208		size_t passphrase_len, uint8_t plaintext[/! ciphertext_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH /], Tox_Err_Decryption *error);
209
210		/*******************************************************************************
211		*
212		* BEGIN PART 2
213		*
214		* And now part 2, which does the actual encryption, and can be used to write
215		* less CPU intensive client code than part one.
216		*
217		******************************************************************************/
218
219		/**
220		* This type represents a pass-key.
221		*
222		* A pass-key and a password are two different concepts: a password is given
223		* by the user in plain text. A pass-key is the generated symmetric key used
224		* for encryption and decryption. It is derived from a salt and the
225		* user-provided password.
226		*
227		* The Tox_Pass_Key structure is hidden in the implementation. It can be created
228		* using tox_pass_key_derive or tox_pass_key_derive_with_salt and must be
229		* deallocated using tox_pass_key_free.
230		*/
231		typedef struct Tox_Pass_Key Tox_Pass_Key;
232
233		/**
234		* Deallocate a Tox_Pass_Key. This function behaves like `free()`, so NULL is an
235		* acceptable argument value.
236		*/
237		void tox_pass_key_free(Tox_Pass_Key *key);
238
239		/**
240		* Generates a secret symmetric key from the given passphrase.
241		*
242		* Be sure to not compromise the key! Only keep it in memory, do not write
243		* it to disk.
244		*
245		* Note that this function is not deterministic; to derive the same key from
246		* a password, you also must know the random salt that was used. A
247		* deterministic version of this function is `tox_pass_key_derive_with_salt`.
248		*
249		* @param passphrase The user-provided password. Can be empty.
250		* @param passphrase_len The length of the password.
251		*
252		* @return new symmetric key on success, NULL on failure.
253		*/
254		Tox_Pass_Key *tox_pass_key_derive(
255		const uint8_t passphrase[], size_t passphrase_len,
256		Tox_Err_Key_Derivation *error);
257
258		/**
259		* Same as above, except use the given salt for deterministic key derivation.
260		*
261		* @param passphrase The user-provided password. Can be empty.
262		* @param passphrase_len The length of the password.
263		* @param salt An array of exactly TOX_PASS_SALT_LENGTH bytes.
264		*
265		* @return new symmetric key on success, NULL on failure.
266		*/
267		Tox_Pass_Key *tox_pass_key_derive_with_salt(
268		const uint8_t passphrase[], size_t passphrase_len,
269		const Tox_Pass_Salt salt, Tox_Err_Key_Derivation *error);
270
271		/**
272		* Encrypt a plain text with a key produced by tox_pass_key_derive or
273		* tox_pass_key_derive_with_salt.
274		*
275		* The output array must be at least
276		* `plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH` bytes long.
277		*
278		* @param plaintext A byte array of length `plaintext_len`.
279		* @param plaintext_len The length of the plain text array. Bigger than 0.
280		* @param ciphertext The cipher text array to write the encrypted data to.
281		*
282		* @return true on success.
283		*/
284		bool tox_pass_key_encrypt(const Tox_Pass_Key *key, const uint8_t plaintext[], size_t plaintext_len,
285		uint8_t ciphertext[/! plaintext_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH /], Tox_Err_Encryption *error);
286
287		/**
288		* This is the inverse of tox_pass_key_encrypt, also using only keys produced by
289		* tox_pass_key_derive or tox_pass_key_derive_with_salt.
290		*
291		* @param ciphertext A byte array of length `ciphertext_len`.
292		* @param ciphertext_len The length of the cipher text array. At least
293		* TOX_PASS_ENCRYPTION_EXTRA_LENGTH.
294		* @param plaintext The plain text array to write the decrypted data to.
295		*
296		* @return true on success.
297		*/
298		bool tox_pass_key_decrypt(const Tox_Pass_Key *key, const uint8_t ciphertext[], size_t ciphertext_len,
299		uint8_t plaintext[/! ciphertext_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH /], Tox_Err_Decryption *error);
300
301		typedef enum Tox_Err_Get_Salt {
302
303		/**
304		* The function returned successfully.
305		*/
306		TOX_ERR_GET_SALT_OK,
307
308		/**
309		* One of the arguments to the function was NULL when it was not expected.
310		*/
311		TOX_ERR_GET_SALT_NULL,
312
313		/**
314		* The input data is missing the magic number (i.e. wasn't created by this
315		* module, or is corrupted).
316		*/
317		TOX_ERR_GET_SALT_BAD_FORMAT,
318
319		} Tox_Err_Get_Salt;
320
321		const char *tox_err_get_salt_to_string(Tox_Err_Get_Salt error);
322
323		/**
324		* Retrieves the salt used to encrypt the given data.
325		*
326		* The retrieved salt can then be passed to tox_pass_key_derive_with_salt to
327		* produce the same key as was previously used. Any data encrypted with this
328		* module can be used as input.
329		*
330		* The cipher text must be at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes in
331		* length.
332		* The salt must be TOX_PASS_SALT_LENGTH bytes in length.
333		* If the passed byte arrays are smaller than required, the behaviour is
334		* undefined.
335		*
336		* If the cipher text pointer or the salt is NULL, this function returns false.
337		*
338		* Success does not say anything about the validity of the data, only that
339		* data of the appropriate size was copied.
340		*
341		* @param ciphertext The encrypted data; at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes are read.
342		* @param salt An array of exactly TOX_PASS_SALT_LENGTH bytes to write the salt to.
343		*
344		* @return true on success.
345		*/
346		bool tox_get_salt(
347		const uint8_t ciphertext[TOX_PASS_ENCRYPTION_EXTRA_LENGTH],
348		Tox_Pass_Salt salt, Tox_Err_Get_Salt *error);
349
350		/**
351		* Determines whether or not the given data is encrypted by this module.
352		*
353		* It does this check by verifying that the magic number is the one put in
354		* place by the encryption functions.
355		*
356		* The data must be at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes in length.
357		* If the passed byte array is smaller than required, the behaviour is
358		* undefined.
359		*
360		* If the data pointer is NULL, the behaviour is undefined
361		*
362		* @param data The data to check; at least TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes are read.
363		*
364		* @return true if the data is encrypted by this module.
365		*/
366		bool tox_is_data_encrypted(const uint8_t data[TOX_PASS_ENCRYPTION_EXTRA_LENGTH]);
367
368		#ifdef __cplusplus
369		} /* extern "C" */
370		#endif
371
372		//!TOKSTYLE-
373
374		typedef Tox_Err_Key_Derivation TOX_ERR_KEY_DERIVATION;
375		typedef Tox_Err_Encryption TOX_ERR_ENCRYPTION;
376		typedef Tox_Err_Decryption TOX_ERR_DECRYPTION;
377		typedef Tox_Err_Get_Salt TOX_ERR_GET_SALT;
378
379		//!TOKSTYLE+
380
381		#endif /* C_TOXCORE_TOXENCRYPTSAVE_TOXENCRYPTSAVE_H */