10.5. Authenticated encryption with associated data (AEAD)

10.5.1. AEAD algorithms

PSA_ALG_CCM (macro)

The Counter with CBC-MAC (CCM) authenticated encryption algorithm.

#define PSA_ALG_CCM ((psa_algorithm_t)0x05500100)

CCM is defined for block ciphers that have a 128-bit block size. The underlying block cipher is determined by the key type.

To use PSA_ALG_CCM with a multi-part AEAD operation, the application must call psa_aead_set_lengths() before providing the nonce, the additional data and plaintext to the operation.

CCM requires a nonce of between 7 and 13 bytes in length. The length of the nonce depends on the length of the plaintext:

  • CCM encodes the plaintext length pLen in L octets, with L the smallest integer >= 2 where pLen < 2^(8L).

  • The nonce length is then 15 - L bytes.

If the application is generating a random nonce using psa_aead_generate_nonce(), the size of the generated nonce is 15 - L bytes.

CCM supports authentication tag sizes of 4, 6, 8, 10, 12, 14, and 16 bytes. The default tag length is 16. Shortened tag lengths can be requested using PSA_ALG_AEAD_WITH_SHORTENED_TAG(PSA_ALG_CCM, tag_length), where tag_length is a valid CCM tag length.

The CCM block cipher mode is defined in Counter with CBC-MAC (CCM) [RFC3610].

PSA_ALG_GCM (macro)

The Galois/Counter Mode (GCM) authenticated encryption algorithm.

#define PSA_ALG_GCM ((psa_algorithm_t)0x05500200)

GCM is defined for block ciphers that have a 128-bit block size. The underlying block cipher is determined by the key type.

GCM requires a nonce of at least 1 byte in length. The maximum supported nonce size is implementation defined. Calling psa_aead_generate_nonce() will generate a random 12-byte nonce.

GCM supports authentication tag sizes of 4, 8, 12, 13, 14, 15, and 16 bytes. The default tag length is 16. Shortened tag lengths can be requested using PSA_ALG_AEAD_WITH_SHORTENED_TAG(PSA_ALG_GCM, tag_length), where tag_length is a valid GCM tag length.

The GCM block cipher mode is defined in NIST Special Publication 800-38D: Recommendation for Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC [SP800-38D].

PSA_ALG_CHACHA20_POLY1305 (macro)

The ChaCha20-Poly1305 AEAD algorithm.

#define PSA_ALG_CHACHA20_POLY1305 ((psa_algorithm_t)0x05100500)

There are two defined variants of ChaCha20-Poly1305:

  • An implementation that supports ChaCha20-Poly1305 must support the variant defined by ChaCha20 and Poly1305 for IETF Protocols [RFC7539], which has a 96-bit nonce and 32-bit counter.

  • An implementation can optionally also support the original variant defined by ChaCha, a variant of Salsa20 [CHACHA20], which has a 64-bit nonce and 64-bit counter.

The variant used for the AEAD encryption or decryption operation, depends on the nonce provided for an AEAD operation using PSA_ALG_CHACHA20_POLY1305:

Implementations must support 16-byte tags. It is recommended that truncated tag sizes are rejected.

PSA_ALG_AEAD_WITH_SHORTENED_TAG (macro)

Macro to build a AEAD algorithm with a shortened tag.

#define PSA_ALG_AEAD_WITH_SHORTENED_TAG(aead_alg, tag_length) \
    /* specification-defined value */

Parameters

aead_alg

An AEAD algorithm identifier (value of type psa_algorithm_t such that PSA_ALG_IS_AEAD(alg) is true).

tag_length

Desired length of the authentication tag in bytes.

Returns

The corresponding AEAD algorithm with the specified tag length.

Unspecified if alg is not a supported AEAD algorithm or if tag_length is not valid for the specified AEAD algorithm.

Description

An AEAD algorithm with a shortened tag is similar to the corresponding AEAD algorithm, but has an authentication tag that consists of fewer bytes. Depending on the algorithm, the tag length might affect the calculation of the ciphertext.

The AEAD algorithm with a default length tag can be recovered using PSA_ALG_AEAD_WITH_DEFAULT_LENGTH_TAG().

10.5.2. Single-part AEAD functions

psa_aead_encrypt (function)

Process an authenticated encryption operation.

psa_status_t psa_aead_encrypt(psa_key_id_t key,
                              psa_algorithm_t alg,
                              const uint8_t * nonce,
                              size_t nonce_length,
                              const uint8_t * additional_data,
                              size_t additional_data_length,
                              const uint8_t * plaintext,
                              size_t plaintext_length,
                              uint8_t * ciphertext,
                              size_t ciphertext_size,
                              size_t * ciphertext_length);

Parameters

key

Identifier of the key to use for the operation. It must allow the usage PSA_KEY_USAGE_ENCRYPT.

alg

The AEAD algorithm to compute (PSA_ALG_XXX value such that PSA_ALG_IS_AEAD(alg) is true).

nonce

Nonce or IV to use.

nonce_length

Size of the nonce buffer in bytes. This must be appropriate for the selected algorithm. The default nonce size is PSA_AEAD_NONCE_LENGTH(key_type, alg) where key_type is the type of key.

additional_data

Additional data that will be authenticated but not encrypted.

additional_data_length

Size of additional_data in bytes.

plaintext

Data that will be authenticated and encrypted.

plaintext_length

Size of plaintext in bytes.

ciphertext

Output buffer for the authenticated and encrypted data. The additional data is not part of this output. For algorithms where the encrypted data and the authentication tag are defined as separate outputs, the authentication tag is appended to the encrypted data.

ciphertext_size

Size of the ciphertext buffer in bytes. This must be appropriate for the selected algorithm and key:

ciphertext_length

On success, the size of the output in the ciphertext buffer.

Returns: psa_status_t

PSA_SUCCESS

Success.

PSA_ERROR_INVALID_HANDLE
PSA_ERROR_NOT_PERMITTED

The key does not have the PSA_KEY_USAGE_ENCRYPT flag, or it does not permit the requested algorithm.

PSA_ERROR_INVALID_ARGUMENT

key is not compatible with alg.

PSA_ERROR_NOT_SUPPORTED

alg is not supported or is not an AEAD algorithm.

PSA_ERROR_INSUFFICIENT_MEMORY
PSA_ERROR_BUFFER_TOO_SMALL

ciphertext_size is too small. PSA_AEAD_ENCRYPT_OUTPUT_SIZE() or PSA_AEAD_ENCRYPT_OUTPUT_MAX_SIZE() can be used to determine the required buffer size.

PSA_ERROR_COMMUNICATION_FAILURE
PSA_ERROR_HARDWARE_FAILURE
PSA_ERROR_CORRUPTION_DETECTED
PSA_ERROR_STORAGE_FAILURE
PSA_ERROR_DATA_CORRUPT
PSA_ERROR_DATA_INVALID
PSA_ERROR_BAD_STATE

The library has not been previously initialized by psa_crypto_init(). It is implementation-dependent whether a failure to initialize results in this error code.

psa_aead_decrypt (function)

Process an authenticated decryption operation.

psa_status_t psa_aead_decrypt(psa_key_id_t key,
                              psa_algorithm_t alg,
                              const uint8_t * nonce,
                              size_t nonce_length,
                              const uint8_t * additional_data,
                              size_t additional_data_length,
                              const uint8_t * ciphertext,
                              size_t ciphertext_length,
                              uint8_t * plaintext,
                              size_t plaintext_size,
                              size_t * plaintext_length);

Parameters

key

Identifier of the key to use for the operation. It must allow the usage PSA_KEY_USAGE_DECRYPT.

alg

The AEAD algorithm to compute (PSA_ALG_XXX value such that PSA_ALG_IS_AEAD(alg) is true).

nonce

Nonce or IV to use.

nonce_length

Size of the nonce buffer in bytes. This must be appropriate for the selected algorithm. The default nonce size is PSA_AEAD_NONCE_LENGTH(key_type, alg) where key_type is the type of key.

additional_data

Additional data that has been authenticated but not encrypted.

additional_data_length

Size of additional_data in bytes.

ciphertext

Data that has been authenticated and encrypted. For algorithms where the encrypted data and the authentication tag are defined as separate inputs, the buffer must contain the encrypted data followed by the authentication tag.

ciphertext_length

Size of ciphertext in bytes.

plaintext

Output buffer for the decrypted data.

plaintext_size

Size of the plaintext buffer in bytes. This must be appropriate for the selected algorithm and key:

plaintext_length

On success, the size of the output in the plaintext buffer.

Returns: psa_status_t

PSA_SUCCESS

Success.

PSA_ERROR_INVALID_HANDLE
PSA_ERROR_INVALID_SIGNATURE

The ciphertext is not authentic.

PSA_ERROR_NOT_PERMITTED

The key does not have the PSA_KEY_USAGE_DECRYPT flag, or it does not permit the requested algorithm.

PSA_ERROR_INVALID_ARGUMENT

key is not compatible with alg.

PSA_ERROR_NOT_SUPPORTED

alg is not supported or is not an AEAD algorithm.

PSA_ERROR_INSUFFICIENT_MEMORY
PSA_ERROR_BUFFER_TOO_SMALL

plaintext_size is too small. PSA_AEAD_DECRYPT_OUTPUT_SIZE() or PSA_AEAD_DECRYPT_OUTPUT_MAX_SIZE() can be used to determine the required buffer size.

PSA_ERROR_COMMUNICATION_FAILURE
PSA_ERROR_HARDWARE_FAILURE
PSA_ERROR_CORRUPTION_DETECTED
PSA_ERROR_STORAGE_FAILURE
PSA_ERROR_DATA_CORRUPT
PSA_ERROR_DATA_INVALID
PSA_ERROR_BAD_STATE

The library has not been previously initialized by psa_crypto_init(). It is implementation-dependent whether a failure to initialize results in this error code.

10.5.3. Multi-part AEAD operations

Warning

When decrypting using a multi-part AEAD operation, there is no guarantee that the input or output is valid until psa_aead_verify() has returned PSA_SUCCESS.

A call to psa_aead_update() or psa_aead_update_ad() returning PSA_SUCCESS does not indicate that the input and output is valid.

Until an application calls psa_aead_verify() and it has returned PSA_SUCCESS, the following rules apply to input and output data from a multi-part AEAD operation:

  • Do not trust the input. If the application takes any action that depends on the input data, this action will need to be undone if the input turns out to be invalid.

  • Store the output in a confidential location. In particular, the application must not copy the output to a memory or storage space which is shared.

  • Do not trust the output. If the application takes any action that depends on the tentative decrypted data, this action will need to be undone if the input turns out to be invalid. Furthermore, if an adversary can observe that this action took place, for example, through timing, they might be able to use this fact as an oracle to decrypt any message encrypted with the same key.

An application that does not follow these rules might be vulnerable to maliciously constructed AEAD input data.

psa_aead_operation_t (type)

The type of the state object for multi-part AEAD operations.

typedef /* implementation-defined type */ psa_aead_operation_t;

Before calling any function on an AEAD operation object, the application must initialize it by any of the following means:

This is an implementation-defined type. Applications that make assumptions about the content of this object will result in in implementation-specific behavior, and are non-portable.

PSA_AEAD_OPERATION_INIT (macro)

This macro returns a suitable initializer for an AEAD operation object of type psa_aead_operation_t.

#define PSA_AEAD_OPERATION_INIT /* implementation-defined value */

psa_aead_operation_init (function)

Return an initial value for an AEAD operation object.

psa_aead_operation_t psa_aead_operation_init(void);

Returns: psa_aead_operation_t

psa_aead_encrypt_setup (function)

Set the key for a multi-part authenticated encryption operation.

psa_status_t psa_aead_encrypt_setup(psa_aead_operation_t * operation,
                                    psa_key_id_t key,
                                    psa_algorithm_t alg);

Parameters

operation

The operation object to set up. It must have been initialized as per the documentation for psa_aead_operation_t and not yet in use.

key

Identifier of the key to use for the operation. It must remain valid until the operation terminates. It must allow the usage PSA_KEY_USAGE_ENCRYPT.

alg

The AEAD algorithm to compute (PSA_ALG_XXX value such that PSA_ALG_IS_AEAD(alg) is true).

Returns: psa_status_t

PSA_SUCCESS

Success.

PSA_ERROR_BAD_STATE

The operation state is not valid: it must be inactive.

PSA_ERROR_INVALID_HANDLE
PSA_ERROR_NOT_PERMITTED

The key does not have the PSA_KEY_USAGE_ENCRYPT flag, or it does not permit the requested algorithm.

PSA_ERROR_INVALID_ARGUMENT

key is not compatible with alg.

PSA_ERROR_NOT_SUPPORTED

alg is not supported or is not an AEAD algorithm.

PSA_ERROR_INSUFFICIENT_MEMORY
PSA_ERROR_COMMUNICATION_FAILURE
PSA_ERROR_HARDWARE_FAILURE
PSA_ERROR_CORRUPTION_DETECTED
PSA_ERROR_STORAGE_FAILURE
PSA_ERROR_DATA_CORRUPT
PSA_ERROR_DATA_INVALID
PSA_ERROR_BAD_STATE

The library has not been previously initialized by psa_crypto_init(). It is implementation-dependent whether a failure to initialize results in this error code.

Description

The sequence of operations to encrypt a message with authentication is as follows:

  1. Allocate an operation object which will be passed to all the functions listed here.

  2. Initialize the operation object with one of the methods described in the documentation for psa_aead_operation_t, e.g. PSA_AEAD_OPERATION_INIT.

  3. Call psa_aead_encrypt_setup() to specify the algorithm and key.

  4. If needed, call psa_aead_set_lengths() to specify the length of the inputs to the subsequent calls to psa_aead_update_ad() and psa_aead_update(). See the documentation of psa_aead_set_lengths() for details.

  5. Call either psa_aead_generate_nonce() or psa_aead_set_nonce() to generate or set the nonce. It is recommended to use psa_aead_generate_nonce() unless the protocol being implemented requires a specific nonce value.

  6. Call psa_aead_update_ad() zero, one or more times, passing a fragment of the non-encrypted additional authenticated data each time.

  7. Call psa_aead_update() zero, one or more times, passing a fragment of the message to encrypt each time.

  8. Call psa_aead_finish().

If an error occurs at any step after a call to psa_aead_encrypt_setup(), the operation will need to be reset by a call to psa_aead_abort(). The application can call psa_aead_abort() at any time after the operation has been initialized.

After a successful call to psa_aead_encrypt_setup(), the application must eventually terminate the operation. The following events terminate an operation:

psa_aead_decrypt_setup (function)

Set the key for a multi-part authenticated decryption operation.

psa_status_t psa_aead_decrypt_setup(psa_aead_operation_t * operation,
                                    psa_key_id_t key,
                                    psa_algorithm_t alg);

Parameters

operation

The operation object to set up. It must have been initialized as per the documentation for psa_aead_operation_t and not yet in use.

key

Identifier of the key to use for the operation. It must remain valid until the operation terminates. It must allow the usage PSA_KEY_USAGE_DECRYPT.

alg

The AEAD algorithm to compute (PSA_ALG_XXX value such that PSA_ALG_IS_AEAD(alg) is true).

Returns: psa_status_t

PSA_SUCCESS

Success.

PSA_ERROR_BAD_STATE

The operation state is not valid: it must be inactive.

PSA_ERROR_INVALID_HANDLE
PSA_ERROR_NOT_PERMITTED

The key does not have the PSA_KEY_USAGE_DECRYPT flag, or it does not permit the requested algorithm.

PSA_ERROR_INVALID_ARGUMENT

key is not compatible with alg.

PSA_ERROR_NOT_SUPPORTED

alg is not supported or is not an AEAD algorithm.

PSA_ERROR_INSUFFICIENT_MEMORY
PSA_ERROR_COMMUNICATION_FAILURE
PSA_ERROR_HARDWARE_FAILURE
PSA_ERROR_CORRUPTION_DETECTED
PSA_ERROR_STORAGE_FAILURE
PSA_ERROR_DATA_CORRUPT
PSA_ERROR_DATA_INVALID
PSA_ERROR_BAD_STATE

The library has not been previously initialized by psa_crypto_init(). It is implementation-dependent whether a failure to initialize results in this error code.

Description

The sequence of operations to decrypt a message with authentication is as follows:

  1. Allocate an operation object which will be passed to all the functions listed here.

  2. Initialize the operation object with one of the methods described in the documentation for psa_aead_operation_t, e.g. PSA_AEAD_OPERATION_INIT.

  3. Call psa_aead_decrypt_setup() to specify the algorithm and key.

  4. If needed, call psa_aead_set_lengths() to specify the length of the inputs to the subsequent calls to psa_aead_update_ad() and psa_aead_update(). See the documentation of psa_aead_set_lengths() for details.

  5. Call psa_aead_set_nonce() with the nonce for the decryption.

  6. Call psa_aead_update_ad() zero, one or more times, passing a fragment of the non-encrypted additional authenticated data each time.

  7. Call psa_aead_update() zero, one or more times, passing a fragment of the ciphertext to decrypt each time.

  8. Call psa_aead_verify().

If an error occurs at any step after a call to psa_aead_decrypt_setup(), the operation will need to be reset by a call to psa_aead_abort(). The application can call psa_aead_abort() at any time after the operation has been initialized.

After a successful call to psa_aead_decrypt_setup(), the application must eventually terminate the operation. The following events terminate an operation:

psa_aead_set_lengths (function)

Declare the lengths of the message and additional data for AEAD.

psa_status_t psa_aead_set_lengths(psa_aead_operation_t * operation,
                                  size_t ad_length,
                                  size_t plaintext_length);

Parameters

operation

Active AEAD operation.

ad_length

Size of the non-encrypted additional authenticated data in bytes.

plaintext_length

Size of the plaintext to encrypt in bytes.

Returns: psa_status_t

PSA_SUCCESS

Success.

PSA_ERROR_BAD_STATE

The operation state is not valid: it must be active, and psa_aead_set_nonce() and psa_aead_generate_nonce() must not have been called yet.

PSA_ERROR_INVALID_ARGUMENT

At least one of the lengths is not acceptable for the chosen algorithm.

PSA_ERROR_INSUFFICIENT_MEMORY
PSA_ERROR_COMMUNICATION_FAILURE
PSA_ERROR_HARDWARE_FAILURE
PSA_ERROR_CORRUPTION_DETECTED
PSA_ERROR_BAD_STATE

The library has not been previously initialized by psa_crypto_init(). It is implementation-dependent whether a failure to initialize results in this error code.

Description

The application must call this function before calling psa_aead_set_nonce() or psa_aead_generate_nonce(), if the algorithm for the operation requires it. If the algorithm does not require it, calling this function is optional, but if this function is called then the implementation must enforce the lengths.

  • For PSA_ALG_CCM, calling this function is required.

  • For the other AEAD algorithms defined in this specification, calling this function is not required.

  • For vendor-defined algorithm, refer to the vendor documentation.

If this function returns an error status, the operation enters an error state and must be aborted by calling psa_aead_abort().

psa_aead_generate_nonce (function)

Generate a random nonce for an authenticated encryption operation.

psa_status_t psa_aead_generate_nonce(psa_aead_operation_t * operation,
                                     uint8_t * nonce,
                                     size_t nonce_size,
                                     size_t * nonce_length);

Parameters

operation

Active AEAD operation.

nonce

Buffer where the generated nonce is to be written.

nonce_size

Size of the nonce buffer in bytes. This must be at least PSA_AEAD_NONCE_LENGTH(key_type, alg) where key_type and alg are type of key and the algorithm respectively that were used to set up the AEAD operation.

nonce_length

On success, the number of bytes of the generated nonce.

Returns: psa_status_t

PSA_SUCCESS

Success.

PSA_ERROR_BAD_STATE

The operation state is not valid: it must be an active AEAD encryption operation, with no nonce set.

PSA_ERROR_BAD_STATE

The operation state is not valid: this is an algorithm which requires psa_aead_set_lengths() to be called before setting the nonce.

PSA_ERROR_BUFFER_TOO_SMALL

The size of the nonce buffer is too small. PSA_AEAD_NONCE_LENGTH() or PSA_AEAD_NONCE_MAX_SIZE can be used to determine the required buffer size.

PSA_ERROR_INSUFFICIENT_MEMORY
PSA_ERROR_COMMUNICATION_FAILURE
PSA_ERROR_HARDWARE_FAILURE
PSA_ERROR_CORRUPTION_DETECTED
PSA_ERROR_STORAGE_FAILURE
PSA_ERROR_DATA_CORRUPT
PSA_ERROR_DATA_INVALID
PSA_ERROR_BAD_STATE

The library has not been previously initialized by psa_crypto_init(). It is implementation-dependent whether a failure to initialize results in this error code.

Description

This function generates a random nonce for the authenticated encryption operation with an appropriate size for the chosen algorithm, key type and key size.

The application must call psa_aead_encrypt_setup() before calling this function. If applicable for the algorithm, the application must call psa_aead_set_lengths() before calling this function.

If this function returns an error status, the operation enters an error state and must be aborted by calling psa_aead_abort().

psa_aead_set_nonce (function)

Set the nonce for an authenticated encryption or decryption operation.

psa_status_t psa_aead_set_nonce(psa_aead_operation_t * operation,
                                const uint8_t * nonce,
                                size_t nonce_length);

Parameters

operation

Active AEAD operation.

nonce

Buffer containing the nonce to use.

nonce_length

Size of the nonce in bytes. This must be a valid nonce size for the chosen algorithm. The default nonce size is PSA_AEAD_NONCE_LENGTH(key_type, alg) where key_type and alg are type of key and the algorithm respectively that were used to set up the AEAD operation.

Returns: psa_status_t

PSA_SUCCESS

Success.

PSA_ERROR_BAD_STATE

The operation state is not valid: it must be active, with no nonce set.

PSA_ERROR_BAD_STATE

The operation state is not valid: this is an algorithm which requires psa_aead_set_lengths() to be called before setting the nonce.

PSA_ERROR_INVALID_ARGUMENT

The size of nonce is not acceptable for the chosen algorithm.

PSA_ERROR_INSUFFICIENT_MEMORY
PSA_ERROR_COMMUNICATION_FAILURE
PSA_ERROR_HARDWARE_FAILURE
PSA_ERROR_CORRUPTION_DETECTED
PSA_ERROR_STORAGE_FAILURE
PSA_ERROR_DATA_CORRUPT
PSA_ERROR_DATA_INVALID
PSA_ERROR_BAD_STATE

The library has not been previously initialized by psa_crypto_init(). It is implementation-dependent whether a failure to initialize results in this error code.

Description

This function sets the nonce for the authenticated encryption or decryption operation.

The application must call psa_aead_encrypt_setup() or psa_aead_decrypt_setup() before calling this function. If applicable for the algorithm, the application must call psa_aead_set_lengths() before calling this function.

If this function returns an error status, the operation enters an error state and must be aborted by calling psa_aead_abort().

Note

When encrypting, psa_aead_generate_nonce() is recommended instead of using this function, unless implementing a protocol that requires a non-random IV.

psa_aead_update_ad (function)

Pass additional data to an active AEAD operation.

psa_status_t psa_aead_update_ad(psa_aead_operation_t * operation,
                                const uint8_t * input,
                                size_t input_length);

Parameters

operation

Active AEAD operation.

input

Buffer containing the fragment of additional data.

input_length

Size of the input buffer in bytes.

Returns: psa_status_t

PSA_SUCCESS

Success.

Warning

When decrypting, do not trust the input until psa_aead_verify() succeeds.

See the detailed warning.

PSA_ERROR_BAD_STATE

The operation state is not valid: it must be active, have a nonce set, have lengths set if required by the algorithm, and psa_aead_update() must not have been called yet.

PSA_ERROR_INVALID_ARGUMENT

The total input length overflows the additional data length that was previously specified with psa_aead_set_lengths().

PSA_ERROR_INSUFFICIENT_MEMORY
PSA_ERROR_COMMUNICATION_FAILURE
PSA_ERROR_HARDWARE_FAILURE
PSA_ERROR_CORRUPTION_DETECTED
PSA_ERROR_STORAGE_FAILURE
PSA_ERROR_DATA_CORRUPT
PSA_ERROR_DATA_INVALID
PSA_ERROR_BAD_STATE

The library has not been previously initialized by psa_crypto_init(). It is implementation-dependent whether a failure to initialize results in this error code.

Description

Additional data is authenticated, but not encrypted.

This function can be called multiple times to pass successive fragments of the additional data. This function must not be called after passing data to encrypt or decrypt with psa_aead_update().

The following must occur before calling this function:

  1. Call either psa_aead_encrypt_setup() or psa_aead_decrypt_setup().

  2. Set the nonce with psa_aead_generate_nonce() or psa_aead_set_nonce().

If this function returns an error status, the operation enters an error state and must be aborted by calling psa_aead_abort().

psa_aead_update (function)

Encrypt or decrypt a message fragment in an active AEAD operation.

psa_status_t psa_aead_update(psa_aead_operation_t * operation,
                             const uint8_t * input,
                             size_t input_length,
                             uint8_t * output,
                             size_t output_size,
                             size_t * output_length);

Parameters

operation

Active AEAD operation.

input

Buffer containing the message fragment to encrypt or decrypt.

input_length

Size of the input buffer in bytes.

output

Buffer where the output is to be written.

output_size

Size of the output buffer in bytes. This must be appropriate for the selected algorithm and key:

  • A sufficient output size is PSA_AEAD_UPDATE_OUTPUT_SIZE(key_type, alg, input_length) where key_type is the type of key and alg is the algorithm that were used to set up the operation.

  • PSA_AEAD_UPDATE_OUTPUT_MAX_SIZE(input_length) evaluates to the maximum output size of any supported AEAD algorithm.

output_length

On success, the number of bytes that make up the returned output.

Returns: psa_status_t

PSA_SUCCESS

Success.

Warning

When decrypting, do not use the output until psa_aead_verify() succeeds.

See the detailed warning.

PSA_ERROR_BAD_STATE

The operation state is not valid: it must be active, have a nonce set, and have lengths set if required by the algorithm.

PSA_ERROR_BUFFER_TOO_SMALL

The size of the output buffer is too small. PSA_AEAD_UPDATE_OUTPUT_SIZE() or PSA_AEAD_UPDATE_OUTPUT_MAX_SIZE() can be used to determine the required buffer size.

PSA_ERROR_INVALID_ARGUMENT

The total length of input to psa_aead_update_ad() so far is less than the additional data length that was previously specified with psa_aead_set_lengths().

PSA_ERROR_INVALID_ARGUMENT

The total input length overflows the plaintext length that was previously specified with psa_aead_set_lengths().

PSA_ERROR_INSUFFICIENT_MEMORY
PSA_ERROR_COMMUNICATION_FAILURE
PSA_ERROR_HARDWARE_FAILURE
PSA_ERROR_CORRUPTION_DETECTED
PSA_ERROR_STORAGE_FAILURE
PSA_ERROR_DATA_CORRUPT
PSA_ERROR_DATA_INVALID
PSA_ERROR_BAD_STATE

The library has not been previously initialized by psa_crypto_init(). It is implementation-dependent whether a failure to initialize results in this error code.

Description

The following must occur before calling this function:

  1. Call either psa_aead_encrypt_setup() or psa_aead_decrypt_setup(). The choice of setup function determines whether this function encrypts or decrypts its input.

  2. Set the nonce with psa_aead_generate_nonce() or psa_aead_set_nonce().

  3. Call psa_aead_update_ad() to pass all the additional data.

If this function returns an error status, the operation enters an error state and must be aborted by calling psa_aead_abort().

This function does not require the input to be aligned to any particular block boundary. If the implementation can only process a whole block at a time, it must consume all the input provided, but it might delay the end of the corresponding output until a subsequent call to psa_aead_update(), psa_aead_finish() or psa_aead_verify() provides sufficient input. The amount of data that can be delayed in this way is bounded by PSA_AEAD_UPDATE_OUTPUT_SIZE().

psa_aead_finish (function)

Finish encrypting a message in an AEAD operation.

psa_status_t psa_aead_finish(psa_aead_operation_t * operation,
                             uint8_t * ciphertext,
                             size_t ciphertext_size,
                             size_t * ciphertext_length,
                             uint8_t * tag,
                             size_t tag_size,
                             size_t * tag_length);

Parameters

operation

Active AEAD operation.

ciphertext

Buffer where the last part of the ciphertext is to be written.

ciphertext_size

Size of the ciphertext buffer in bytes. This must be appropriate for the selected algorithm and key:

ciphertext_length

On success, the number of bytes of returned ciphertext.

tag

Buffer where the authentication tag is to be written.

tag_size

Size of the tag buffer in bytes. This must be appropriate for the selected algorithm and key:

tag_length

On success, the number of bytes that make up the returned tag.

Returns: psa_status_t

PSA_SUCCESS

Success.

PSA_ERROR_BAD_STATE

The operation state is not valid: it must be an active encryption operation with a nonce set.

PSA_ERROR_BUFFER_TOO_SMALL

The size of the ciphertext or tag buffer is too small. PSA_AEAD_FINISH_OUTPUT_SIZE() or PSA_AEAD_FINISH_OUTPUT_MAX_SIZE can be used to determine the required ciphertext buffer size. PSA_AEAD_TAG_LENGTH() or PSA_AEAD_TAG_MAX_SIZE can be used to determine the required tag buffer size.

PSA_ERROR_INVALID_ARGUMENT

The total length of input to psa_aead_update_ad() so far is less than the additional data length that was previously specified with psa_aead_set_lengths().

PSA_ERROR_INVALID_ARGUMENT

The total length of input to psa_aead_update() so far is less than the plaintext length that was previously specified with psa_aead_set_lengths().

PSA_ERROR_INSUFFICIENT_MEMORY
PSA_ERROR_COMMUNICATION_FAILURE
PSA_ERROR_HARDWARE_FAILURE
PSA_ERROR_CORRUPTION_DETECTED
PSA_ERROR_STORAGE_FAILURE
PSA_ERROR_DATA_CORRUPT
PSA_ERROR_DATA_INVALID
PSA_ERROR_BAD_STATE

The library has not been previously initialized by psa_crypto_init(). It is implementation-dependent whether a failure to initialize results in this error code.

Description

The operation must have been set up with psa_aead_encrypt_setup().

This function finishes the authentication of the additional data formed by concatenating the inputs passed to preceding calls to psa_aead_update_ad() with the plaintext formed by concatenating the inputs passed to preceding calls to psa_aead_update().

This function has two output buffers:

  • ciphertext contains trailing ciphertext that was buffered from preceding calls to psa_aead_update().

  • tag contains the authentication tag.

When this function returns successfully, the operation becomes inactive. If this function returns an error status, the operation enters an error state and must be aborted by calling psa_aead_abort().

psa_aead_verify (function)

Finish authenticating and decrypting a message in an AEAD operation.

psa_status_t psa_aead_verify(psa_aead_operation_t * operation,
                             uint8_t * plaintext,
                             size_t plaintext_size,
                             size_t * plaintext_length,
                             const uint8_t * tag,
                             size_t tag_length);

Parameters

operation

Active AEAD operation.

plaintext

Buffer where the last part of the plaintext is to be written. This is the remaining data from previous calls to psa_aead_update() that could not be processed until the end of the input.

plaintext_size

Size of the plaintext buffer in bytes. This must be appropriate for the selected algorithm and key:

plaintext_length

On success, the number of bytes of returned plaintext.

tag

Buffer containing the authentication tag.

tag_length

Size of the tag buffer in bytes.

Returns: psa_status_t

PSA_SUCCESS

Success.

PSA_ERROR_INVALID_SIGNATURE

The calculations were successful, but the authentication tag is not correct.

PSA_ERROR_BAD_STATE

The operation state is not valid: it must be an active decryption operation with a nonce set.

PSA_ERROR_BUFFER_TOO_SMALL

The size of the plaintext buffer is too small. PSA_AEAD_VERIFY_OUTPUT_SIZE() or PSA_AEAD_VERIFY_OUTPUT_MAX_SIZE can be used to determine the required buffer size.

PSA_ERROR_INVALID_ARGUMENT

The total length of input to psa_aead_update_ad() so far is less than the additional data length that was previously specified with psa_aead_set_lengths().

PSA_ERROR_INVALID_ARGUMENT

The total length of input to psa_aead_update() so far is less than the plaintext length that was previously specified with psa_aead_set_lengths().

PSA_ERROR_INSUFFICIENT_MEMORY
PSA_ERROR_COMMUNICATION_FAILURE
PSA_ERROR_HARDWARE_FAILURE
PSA_ERROR_CORRUPTION_DETECTED
PSA_ERROR_STORAGE_FAILURE
PSA_ERROR_DATA_CORRUPT
PSA_ERROR_DATA_INVALID
PSA_ERROR_BAD_STATE

The library has not been previously initialized by psa_crypto_init(). It is implementation-dependent whether a failure to initialize results in this error code.

Description

The operation must have been set up with psa_aead_decrypt_setup().

This function finishes the authenticated decryption of the message components:

  • The additional data consisting of the concatenation of the inputs passed to preceding calls to psa_aead_update_ad().

  • The ciphertext consisting of the concatenation of the inputs passed to preceding calls to psa_aead_update().

  • The tag passed to this function call.

If the authentication tag is correct, this function outputs any remaining plaintext and reports success. If the authentication tag is not correct, this function returns PSA_ERROR_INVALID_SIGNATURE.

When this function returns successfully, the operation becomes inactive. If this function returns an error status, the operation enters an error state and must be aborted by calling psa_aead_abort().

Note

Implementations must make the best effort to ensure that the comparison between the actual tag and the expected tag is performed in constant time.

psa_aead_abort (function)

Abort an AEAD operation.

psa_status_t psa_aead_abort(psa_aead_operation_t * operation);

Parameters

operation

Initialized AEAD operation.

Returns: psa_status_t

PSA_SUCCESS
PSA_ERROR_COMMUNICATION_FAILURE
PSA_ERROR_HARDWARE_FAILURE
PSA_ERROR_CORRUPTION_DETECTED
PSA_ERROR_BAD_STATE

The library has not been previously initialized by psa_crypto_init(). It is implementation-dependent whether a failure to initialize results in this error code.

Description

Aborting an operation frees all associated resources except for the operation object itself. Once aborted, the operation object can be reused for another operation by calling psa_aead_encrypt_setup() or psa_aead_decrypt_setup() again.

This function can be called any time after the operation object has been initialized as described in psa_aead_operation_t.

In particular, calling psa_aead_abort() after the operation has been terminated by a call to psa_aead_abort(), psa_aead_finish() or psa_aead_verify() is safe and has no effect.

10.5.4. Support macros

PSA_ALG_IS_AEAD_ON_BLOCK_CIPHER (macro)

Whether the specified algorithm is an AEAD mode on a block cipher.

#define PSA_ALG_IS_AEAD_ON_BLOCK_CIPHER(alg) /* specification-defined value */

Parameters

alg

An algorithm identifier (value of type psa_algorithm_t).

Returns

1 if alg is an AEAD algorithm which is an AEAD mode based on a block cipher, 0 otherwise.

This macro can return either 0 or 1 if alg is not a supported algorithm identifier.

PSA_ALG_AEAD_WITH_DEFAULT_LENGTH_TAG (macro)

An AEAD algorithm with the default tag length.

#define PSA_ALG_AEAD_WITH_DEFAULT_LENGTH_TAG(aead_alg) \
    /* specification-defined value */

Parameters

aead_alg

An AEAD algorithm (PSA_ALG_XXX value such that PSA_ALG_IS_AEAD(alg) is true).

Returns

The corresponding AEAD algorithm with the default tag length for that algorithm.

Description

This macro can be used to construct the AEAD algorithm with default tag length from an AEAD algorithm with a shortened tag. See also PSA_ALG_AEAD_WITH_SHORTENED_TAG().

PSA_AEAD_ENCRYPT_OUTPUT_SIZE (macro)

The maximum size of the output of psa_aead_encrypt(), in bytes.

#define PSA_AEAD_ENCRYPT_OUTPUT_SIZE(key_type, alg, plaintext_length) \
    /* implementation-defined value */

Parameters

key_type

A symmetric key type that is compatible with algorithm alg.

alg

An AEAD algorithm (PSA_ALG_XXX value such that PSA_ALG_IS_AEAD(alg) is true).

plaintext_length

Size of the plaintext in bytes.

Returns

The AEAD ciphertext size for the specified key type and algorithm. If the key type or AEAD algorithm is not recognized, or the parameters are incompatible, return 0. An implementation can return either 0 or a correct size for a key type and AEAD algorithm that it recognizes, but does not support.

Description

If the size of the ciphertext buffer is at least this large, it is guaranteed that psa_aead_encrypt() will not fail due to an insufficient buffer size. Depending on the algorithm, the actual size of the ciphertext might be smaller.

See also PSA_AEAD_ENCRYPT_OUTPUT_MAX_SIZE.

PSA_AEAD_ENCRYPT_OUTPUT_MAX_SIZE (macro)

A sufficient output buffer size for psa_aead_encrypt(), for any of the supported key types and AEAD algorithms.

#define PSA_AEAD_ENCRYPT_OUTPUT_MAX_SIZE(plaintext_length) \
    /* implementation-defined value */

Parameters

plaintext_length

Size of the plaintext in bytes.

Description

If the size of the ciphertext buffer is at least this large, it is guaranteed that psa_aead_encrypt() will not fail due to an insufficient buffer size.

See also PSA_AEAD_ENCRYPT_OUTPUT_SIZE().

PSA_AEAD_DECRYPT_OUTPUT_SIZE (macro)

The maximum size of the output of psa_aead_decrypt(), in bytes.

#define PSA_AEAD_DECRYPT_OUTPUT_SIZE(key_type, alg, ciphertext_length) \
    /* implementation-defined value */

Parameters

key_type

A symmetric key type that is compatible with algorithm alg.

alg

An AEAD algorithm (PSA_ALG_XXX value such that PSA_ALG_IS_AEAD(alg) is true).

ciphertext_length

Size of the ciphertext in bytes.

Returns

The AEAD plaintext size for the specified key type and algorithm. If the key type or AEAD algorithm is not recognized, or the parameters are incompatible, return 0. An implementation can return either 0 or a correct size for a key type and AEAD algorithm that it recognizes, but does not support.

Description

If the size of the plaintext buffer is at least this large, it is guaranteed that psa_aead_decrypt() will not fail due to an insufficient buffer size. Depending on the algorithm, the actual size of the plaintext might be smaller.

See also PSA_AEAD_DECRYPT_OUTPUT_MAX_SIZE.

PSA_AEAD_DECRYPT_OUTPUT_MAX_SIZE (macro)

A sufficient output buffer size for psa_aead_decrypt(), for any of the supported key types and AEAD algorithms.

#define PSA_AEAD_DECRYPT_OUTPUT_MAX_SIZE(ciphertext_length) \
    /* implementation-defined value */

Parameters

ciphertext_length

Size of the ciphertext in bytes.

Description

If the size of the plaintext buffer is at least this large, it is guaranteed that psa_aead_decrypt() will not fail due to an insufficient buffer size.

See also PSA_AEAD_DECRYPT_OUTPUT_SIZE().

PSA_AEAD_NONCE_LENGTH (macro)

The default nonce size for an AEAD algorithm, in bytes.

#define PSA_AEAD_NONCE_LENGTH(key_type, alg) /* implementation-defined value */

Parameters

key_type

A symmetric key type that is compatible with algorithm alg.

alg

An AEAD algorithm (PSA_ALG_XXX value such that PSA_ALG_IS_AEAD(alg) is true).

Returns

The default nonce size for the specified key type and algorithm. If the key type or AEAD algorithm is not recognized, or the parameters are incompatible, return 0. An implementation can return either 0 or a correct size for a key type and AEAD algorithm that it recognizes, but does not support.

Description

This macro can be used to allocate a buffer of sufficient size to store the nonce output from psa_aead_generate_nonce().

See also PSA_AEAD_NONCE_MAX_SIZE.

PSA_AEAD_NONCE_MAX_SIZE (macro)

The maximum nonce size for all supported AEAD algorithms, in bytes.

#define PSA_AEAD_NONCE_MAX_SIZE /* implementation-defined value */

See also PSA_AEAD_NONCE_LENGTH().

PSA_AEAD_UPDATE_OUTPUT_SIZE (macro)

A sufficient output buffer size for psa_aead_update().

#define PSA_AEAD_UPDATE_OUTPUT_SIZE(key_type, alg, input_length) \
    /* implementation-defined value */

Parameters

key_type

A symmetric key type that is compatible with algorithm alg.

alg

An AEAD algorithm (PSA_ALG_XXX value such that PSA_ALG_IS_AEAD(alg) is true).

input_length

Size of the input in bytes.

Returns

A sufficient output buffer size for the specified key type and algorithm. If the key type or AEAD algorithm is not recognized, or the parameters are incompatible, return 0. An implementation can return either 0 or a correct size for a key type and AEAD algorithm that it recognizes, but does not support.

Description

If the size of the output buffer is at least this large, it is guaranteed that psa_aead_update() will not fail due to an insufficient buffer size. The actual size of the output might be smaller in any given call.

See also PSA_AEAD_UPDATE_OUTPUT_MAX_SIZE.

PSA_AEAD_UPDATE_OUTPUT_MAX_SIZE (macro)

A sufficient output buffer size for psa_aead_update(), for any of the supported key types and AEAD algorithms.

#define PSA_AEAD_UPDATE_OUTPUT_MAX_SIZE(input_length) \
    /* implementation-defined value */

Parameters

input_length

Size of the input in bytes.

Description

If the size of the output buffer is at least this large, it is guaranteed that psa_aead_update() will not fail due to an insufficient buffer size.

See also PSA_AEAD_UPDATE_OUTPUT_SIZE().

PSA_AEAD_FINISH_OUTPUT_SIZE (macro)

A sufficient ciphertext buffer size for psa_aead_finish().

#define PSA_AEAD_FINISH_OUTPUT_SIZE(key_type, alg) \
    /* implementation-defined value */

Parameters

key_type

A symmetric key type that is compatible with algorithm alg.

alg

An AEAD algorithm (PSA_ALG_XXX value such that PSA_ALG_IS_AEAD(alg) is true).

Returns

A sufficient ciphertext buffer size for the specified key type and algorithm. If the key type or AEAD algorithm is not recognized, or the parameters are incompatible, return 0. An implementation can return either 0 or a correct size for a key type and AEAD algorithm that it recognizes, but does not support.

Description

If the size of the ciphertext buffer is at least this large, it is guaranteed that psa_aead_finish() will not fail due to an insufficient ciphertext buffer size. The actual size of the output might be smaller in any given call.

See also PSA_AEAD_FINISH_OUTPUT_MAX_SIZE.

PSA_AEAD_FINISH_OUTPUT_MAX_SIZE (macro)

A sufficient ciphertext buffer size for psa_aead_finish(), for any of the supported key types and AEAD algorithms.

#define PSA_AEAD_FINISH_OUTPUT_MAX_SIZE /* implementation-defined value */

See also PSA_AEAD_FINISH_OUTPUT_SIZE().

PSA_AEAD_TAG_LENGTH (macro)

The length of a tag for an AEAD algorithm, in bytes.

#define PSA_AEAD_TAG_LENGTH(key_type, key_bits, alg) \
    /* implementation-defined value */

Parameters

key_type

The type of the AEAD key.

key_bits

The size of the AEAD key in bits.

alg

An AEAD algorithm (PSA_ALG_XXX value such that PSA_ALG_IS_AEAD(alg) is true).

Returns

The tag length for the specified algorithm and key. If the AEAD algorithm does not have an identified tag that can be distinguished from the rest of the ciphertext, return 0. If the AEAD algorithm is not recognized, return 0. An implementation can return either 0 or a correct size for an AEAD algorithm that it recognizes, but does not support.

Description

This macro can be used to allocate a buffer of sufficient size to store the tag output from psa_aead_finish().

See also PSA_AEAD_TAG_MAX_SIZE.

PSA_AEAD_TAG_MAX_SIZE (macro)

The maximum tag size for all supported AEAD algorithms, in bytes.

#define PSA_AEAD_TAG_MAX_SIZE /* implementation-defined value */

See also PSA_AEAD_TAG_LENGTH().

PSA_AEAD_VERIFY_OUTPUT_SIZE (macro)

A sufficient plaintext buffer size for psa_aead_verify().

#define PSA_AEAD_VERIFY_OUTPUT_SIZE(key_type, alg) \
    /* implementation-defined value */

Parameters

key_type

A symmetric key type that is compatible with algorithm alg.

alg

An AEAD algorithm (PSA_ALG_XXX value such that PSA_ALG_IS_AEAD(alg) is true).

Returns

A sufficient plaintext buffer size for the specified key type and algorithm. If the key type or AEAD algorithm is not recognized, or the parameters are incompatible, return 0. An implementation can return either 0 or a correct size for a key type and AEAD algorithm that it recognizes, but does not support.

Description

If the size of the plaintext buffer is at least this large, it is guaranteed that psa_aead_verify() will not fail due to an insufficient plaintext buffer size. The actual size of the output might be smaller in any given call.

See also PSA_AEAD_VERIFY_OUTPUT_MAX_SIZE.

PSA_AEAD_VERIFY_OUTPUT_MAX_SIZE (macro)

A sufficient plaintext buffer size for psa_aead_verify(), for any of the supported key types and AEAD algorithms.

#define PSA_AEAD_VERIFY_OUTPUT_MAX_SIZE /* implementation-defined value */

See also PSA_AEAD_VERIFY_OUTPUT_SIZE().