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chachapoly.h File Reference

This file contains the AEAD-ChaCha20-Poly1305 definitions and functions. More...

`#include "mbedtls/private_access.h"`
`#include "mbedtls/build_info.h"`
`#include "mbedtls/poly1305.h"`
`#include "mbedtls/chacha20.h"`
Include dependency graph for chachapoly.h:
This graph shows which files directly or indirectly include this file:

Go to the source code of this file.

## Data Structures

struct | mbedtls_chachapoly_context

## Macros

#define | MBEDTLS_ERR_CHACHAPOLY_BAD_STATE -0x0054
#define | MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED -0x0056

## Typedefs

typedef struct mbedtls_chachapoly_context | mbedtls_chachapoly_context

## Enumerations

enum | mbedtls_chachapoly_mode_t { MBEDTLS_CHACHAPOLY_ENCRYPT , MBEDTLS_CHACHAPOLY_DECRYPT }

## Functions

void | mbedtls_chachapoly_init (mbedtls_chachapoly_context *ctx)
| This function initializes the specified ChaCha20-Poly1305 context.
void | mbedtls_chachapoly_free (mbedtls_chachapoly_context *ctx)
| This function releases and clears the specified ChaCha20-Poly1305 context.
int | mbedtls_chachapoly_setkey (mbedtls_chachapoly_context *ctx, const unsigned char key[32])
| This function sets the ChaCha20-Poly1305 symmetric encryption key.
int | mbedtls_chachapoly_starts (mbedtls_chachapoly_context *ctx, const unsigned char nonce[12], mbedtls_chachapoly_mode_t mode)
| This function starts a ChaCha20-Poly1305 encryption or decryption operation.
int | mbedtls_chachapoly_update_aad (mbedtls_chachapoly_context *ctx, const unsigned char *aad, size_t aad_len)
| This function feeds additional data to be authenticated into an ongoing ChaCha20-Poly1305 operation.
int | mbedtls_chachapoly_update (mbedtls_chachapoly_context *ctx, size_t len, const unsigned char *input, unsigned char *output)
| Thus function feeds data to be encrypted or decrypted into an on-going ChaCha20-Poly1305 operation.
int | mbedtls_chachapoly_finish (mbedtls_chachapoly_context *ctx, unsigned char mac[16])
| This function finished the ChaCha20-Poly1305 operation and generates the MAC (authentication tag).
int | mbedtls_chachapoly_encrypt_and_tag (mbedtls_chachapoly_context *ctx, size_t length, const unsigned char nonce[12], const unsigned char *aad, size_t aad_len, const unsigned char *input, unsigned char *output, unsigned char tag[16])
| This function performs a complete ChaCha20-Poly1305 authenticated encryption with the previously-set key.
int | mbedtls_chachapoly_auth_decrypt (mbedtls_chachapoly_context *ctx, size_t length, const unsigned char nonce[12], const unsigned char *aad, size_t aad_len, const unsigned char tag[16], const unsigned char *input, unsigned char *output)
| This function performs a complete ChaCha20-Poly1305 authenticated decryption with the previously-set key.
int | mbedtls_chachapoly_self_test (int verbose)
| The ChaCha20-Poly1305 checkup routine.

## Detailed Description

This file contains the AEAD-ChaCha20-Poly1305 definitions and functions.

ChaCha20-Poly1305 is an algorithm for Authenticated Encryption with Associated Data (AEAD) that can be used to encrypt and authenticate data. It is based on ChaCha20 and Poly1305 by Daniel Bernstein and was standardized in RFC 7539.

Author
  Daniel King damak.nosp@m.i.gh.nosp@m.@gmai.nosp@m.l.co.nosp@m.m

Definition in file chachapoly.h.

## Macro Definition Documentation

## MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED

#define MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED -0x0056

Authenticated decryption failed: data was not authentic.

Definition at line 32 of file chachapoly.h.

## MBEDTLS_ERR_CHACHAPOLY_BAD_STATE

#define MBEDTLS_ERR_CHACHAPOLY_BAD_STATE -0x0054

The requested operation is not permitted in the current state.

Definition at line 30 of file chachapoly.h.

## Typedef Documentation

## mbedtls_chachapoly_context

typedef struct mbedtls_chachapoly_context mbedtls_chachapoly_context

## Enumeration Type Documentation

## mbedtls_chachapoly_mode_t

enum mbedtls_chachapoly_mode_t

Enumerator
MBEDTLS_CHACHAPOLY_ENCRYPT | The mode value for performing encryption.
MBEDTLS_CHACHAPOLY_DECRYPT | The mode value for performing decryption.

Definition at line 38 of file chachapoly.h.

## Function Documentation

## mbedtls_chachapoly_auth_decrypt()

int mbedtls_chachapoly_auth_decrypt | ( | mbedtls_chachapoly_context * | ctx,
|  | size_t | length,
|  | const unsigned char | nonce[12],
|  | const unsigned char * | aad,
|  | size_t | aad_len,
|  | const unsigned char | tag[16],
|  | const unsigned char * | input,
|  | unsigned char * | output
| ) |  |

This function performs a complete ChaCha20-Poly1305 authenticated decryption with the previously-set key.

Note
  Before using this function, you must set the key with `mbedtls_chachapoly_setkey()`.

Parameters

  ctx | The ChaCha20-Poly1305 context to use (holds the key).
  length | The length (in Bytes) of the data to decrypt.
  nonce | The `96` Bit (`12` bytes) nonce/IV to use.
  aad | The buffer containing the additional authenticated data (AAD). This pointer can be `NULL` if `aad_len == 0`.
  aad_len | The length (in bytes) of the AAD data to process.
  tag | The buffer holding the authentication tag. This must be a readable buffer of length `16` Bytes.
  input | The buffer containing the data to decrypt. This pointer can be `NULL` if `ilen == 0`.
  output | The buffer to where the decrypted data is written. This pointer can be `NULL` if `ilen == 0`.

Returns
  `0` on success.
  MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED if the data was not authentic.
  Another negative error code on other kinds of failure.

## mbedtls_chachapoly_encrypt_and_tag()

int mbedtls_chachapoly_encrypt_and_tag | ( | mbedtls_chachapoly_context * | ctx,
|  | size_t | length,
|  | const unsigned char | nonce[12],
|  | const unsigned char * | aad,
|  | size_t | aad_len,
|  | const unsigned char * | input,
|  | unsigned char * | output,
|  | unsigned char | tag[16]
| ) |  |

This function performs a complete ChaCha20-Poly1305 authenticated encryption with the previously-set key.

Note
  Before using this function, you must set the key with `mbedtls_chachapoly_setkey()`.

Warning
  You must never use the same nonce twice with the same key. This would void any confidentiality and authenticity guarantees for the messages encrypted with the same nonce and key.

Parameters

  ctx | The ChaCha20-Poly1305 context to use (holds the key). This must be initialized.
  length | The length (in bytes) of the data to encrypt or decrypt.
  nonce | The 96-bit (12 bytes) nonce/IV to use.
  aad | The buffer containing the additional authenticated data (AAD). This pointer can be `NULL` if `aad_len == 0`.
  aad_len | The length (in bytes) of the AAD data to process.
  input | The buffer containing the data to encrypt or decrypt. This pointer can be `NULL` if `ilen == 0`.
  output | The buffer to where the encrypted or decrypted data is written. This pointer can be `NULL` if `ilen == 0`.
  tag | The buffer to where the computed 128-bit (16 bytes) MAC is written. This must not be `NULL`.

Returns
  `0` on success.
  A negative error code on failure.

## mbedtls_chachapoly_finish()

int mbedtls_chachapoly_finish | ( | mbedtls_chachapoly_context * | ctx,
|  | unsigned char | mac[16]
| ) |  |

This function finished the ChaCha20-Poly1305 operation and generates the MAC (authentication tag).

Parameters

  ctx | The ChaCha20-Poly1305 context to use. This must be initialized.
  mac | The buffer to where the 128-bit (16 bytes) MAC is written.

Warning
  Decryption with the piecewise API is discouraged, see the warning on `mbedtls_chachapoly_init()`.

Returns
  `0` on success.
  MBEDTLS_ERR_CHACHAPOLY_BAD_STATE if the operation has not been started or has been finished.
  Another negative error code on other kinds of failure.

## mbedtls_chachapoly_free()

void mbedtls_chachapoly_free | ( | mbedtls_chachapoly_context * | ctx | ) |

This function releases and clears the specified ChaCha20-Poly1305 context.

Parameters

  ctx | The ChachaPoly context to clear. This may be `NULL`, in which case this function is a no-op.

## mbedtls_chachapoly_init()

void mbedtls_chachapoly_init | ( | mbedtls_chachapoly_context * | ctx | ) |

This function initializes the specified ChaCha20-Poly1305 context.

                 It must be the first API called before using
                 the context. It must be followed by a call to
                 \c mbedtls_chachapoly_setkey() before any operation can be
                 done, and to \c mbedtls_chachapoly_free() once all
                 operations with that context have been finished.

                 In order to encrypt or decrypt full messages at once, for
                 each message you should make a single call to
                 \c mbedtls_chachapoly_crypt_and_tag() or
                 \c mbedtls_chachapoly_auth_decrypt().

                 In order to encrypt messages piecewise, for each
                 message you should make a call to
                 \c mbedtls_chachapoly_starts(), then 0 or more calls to
                 \c mbedtls_chachapoly_update_aad(), then 0 or more calls to
                 \c mbedtls_chachapoly_update(), then one call to
                 \c mbedtls_chachapoly_finish().

Warning
  Decryption with the piecewise API is discouraged! Always use `mbedtls_chachapoly_auth_decrypt()` when possible!

If however this is not possible because the data is too large to fit in memory, you need to:

- call `mbedtls_chachapoly_starts()` and (if needed) `mbedtls_chachapoly_update_aad()` as above,
- call `mbedtls_chachapoly_update()` multiple times and ensure its output (the plaintext) is NOT used in any other way than placing it in temporary storage at this point,
- call `mbedtls_chachapoly_finish()` to compute the authentication tag and compared it in constant time to the tag received with the ciphertext.

If the tags are not equal, you must immediately discard all previous outputs of `mbedtls_chachapoly_update()`, otherwise you can now safely use the plaintext.

Parameters

  ctx | The ChachaPoly context to initialize. Must not be `NULL`.

## mbedtls_chachapoly_self_test()

int mbedtls_chachapoly_self_test | ( | int | verbose | ) |

The ChaCha20-Poly1305 checkup routine.

Returns
  `0` on success.
  `1` on failure.

## mbedtls_chachapoly_setkey()

int mbedtls_chachapoly_setkey | ( | mbedtls_chachapoly_context * | ctx,
|  | const unsigned char | key[32]
| ) |  |

This function sets the ChaCha20-Poly1305 symmetric encryption key.

Parameters

  ctx | The ChaCha20-Poly1305 context to which the key should be bound. This must be initialized.
  key | The `256` Bit (`32` Bytes) key.

Returns
  `0` on success.
  A negative error code on failure.

## mbedtls_chachapoly_starts()

int mbedtls_chachapoly_starts | ( | mbedtls_chachapoly_context * | ctx,
|  | const unsigned char | nonce[12],
|  | mbedtls_chachapoly_mode_t | mode
| ) |  |

This function starts a ChaCha20-Poly1305 encryption or decryption operation.

Warning
  You must never use the same nonce twice with the same key. This would void any confidentiality and authenticity guarantees for the messages encrypted with the same nonce and key.

Note
  If the context is being used for AAD only (no data to encrypt or decrypt) then `mode` can be set to any value.

Warning
  Decryption with the piecewise API is discouraged, see the warning on `mbedtls_chachapoly_init()`.

Parameters

  ctx | The ChaCha20-Poly1305 context. This must be initialized and bound to a key.
  nonce | The nonce/IV to use for the message. This must be a readable buffer of length `12` Bytes.
  mode | The operation to perform: MBEDTLS_CHACHAPOLY_ENCRYPT or MBEDTLS_CHACHAPOLY_DECRYPT (discouraged, see warning).

Returns
  `0` on success.
  A negative error code on failure.

## mbedtls_chachapoly_update()

int mbedtls_chachapoly_update | ( | mbedtls_chachapoly_context * | ctx,
|  | size_t | len,
|  | const unsigned char * | input,
|  | unsigned char * | output
| ) |  |

Thus function feeds data to be encrypted or decrypted into an on-going ChaCha20-Poly1305 operation.

The direction (encryption or decryption) depends on the mode that was given when calling `mbedtls_chachapoly_starts()`.

You may call this function multiple times to process an arbitrary amount of data. It is permitted to call this function 0 times, if no data is to be encrypted or decrypted.

Warning
  Decryption with the piecewise API is discouraged, see the warning on `mbedtls_chachapoly_init()`.

Parameters

  ctx | The ChaCha20-Poly1305 context to use. This must be initialized.
  len | The length (in bytes) of the data to encrypt or decrypt.
  input | The buffer containing the data to encrypt or decrypt. This pointer can be `NULL` if `len == 0`.
  output | The buffer to where the encrypted or decrypted data is written. This must be able to hold `len` bytes. This pointer can be `NULL` if `len == 0`.

Returns
  `0` on success.
  MBEDTLS_ERR_CHACHAPOLY_BAD_STATE if the operation has not been started or has been finished.
  Another negative error code on other kinds of failure.

## mbedtls_chachapoly_update_aad()

int mbedtls_chachapoly_update_aad | ( | mbedtls_chachapoly_context * | ctx,
|  | const unsigned char * | aad,
|  | size_t | aad_len
| ) |  |

This function feeds additional data to be authenticated into an ongoing ChaCha20-Poly1305 operation.

The Additional Authenticated Data (AAD), also called Associated Data (AD) is only authenticated but not encrypted nor included in the encrypted output. It is usually transmitted separately from the ciphertext or computed locally by each party.

Note
  This function is called before data is encrypted/decrypted. I.e. call this function to process the AAD before calling `mbedtls_chachapoly_update()`.

You may call this function multiple times to process an arbitrary amount of AAD. It is permitted to call this function 0 times, if no AAD is used.

This function cannot be called any more if data has been processed by `mbedtls_chachapoly_update()`, or if the context has been finished.

Warning
  Decryption with the piecewise API is discouraged, see the warning on `mbedtls_chachapoly_init()`.

Parameters

  ctx | The ChaCha20-Poly1305 context. This must be initialized and bound to a key.
  aad_len | The length in Bytes of the AAD. The length has no restrictions.
  aad | Buffer containing the AAD. This pointer can be `NULL` if `aad_len == 0`.

Returns
  `0` on success.
  MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA if `ctx` or `aad` are NULL.
  MBEDTLS_ERR_CHACHAPOLY_BAD_STATE if the operations has not been started or has been finished, or if the AAD has been finished.