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NCBI C++ ToolKit: Symmetric ciphers

The type of the state data structure for multipart cipher operations.

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

• Set the structure to all-bits-zero, for example:

  operation

  Bit operations.

• Initialize the structure to logical zero values, for example:
• Initialize the structure to the initializer PSA_CIPHER_OPERATION_INIT, for example:

  #define PSA_CIPHER_OPERATION_INIT

  This macro returns a suitable initializer for a cipher operation object of type psa_cipher_operation_...

• Assign the result of the function psa_cipher_operation_init() to the structure, for example:

  static psa_cipher_operation_t psa_cipher_operation_init(void)

  Return an initial value for a cipher operation object.

This is an implementation-defined struct. Applications should not make any assumptions about the content of this structure. Implementation details can change in future versions without notice.

Definition at line 1682 of file crypto.h.

Decrypt a message using a symmetric cipher.

This function decrypts a message encrypted with a symmetric cipher.

Parameters

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 cipher algorithm to compute (PSA_ALG_XXX value such that PSA_ALG_IS_CIPHER(alg) is true). [in] input Buffer containing the message to decrypt. This consists of the IV followed by the ciphertext proper. input_length Size of the input buffer in bytes. [out] output Buffer where the plaintext is to be written. output_size Size of the output buffer in bytes. [out] output_length On success, the number of bytes that make up the output.

Return values

Set the key for a multipart symmetric decryption operation.

The sequence of operations to decrypt a message with a symmetric cipher 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_cipher_operation_t, e.g. PSA_CIPHER_OPERATION_INIT.
3. Call psa_cipher_decrypt_setup() to specify the algorithm and key.
4. Call psa_cipher_set_iv() with the IV (initialization vector) for the decryption. If the IV is prepended to the ciphertext, you can call psa_cipher_update() on a buffer containing the IV followed by the beginning of the message.
5. Call psa_cipher_update() zero, one or more times, passing a fragment of the message each time.
6. Call psa_cipher_finish().

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

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

• A successful call to psa_cipher_finish().
• A call to psa_cipher_abort().

Parameters

[in,out] operation The operation object to set up. It must have been initialized as per the documentation for psa_cipher_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 cipher algorithm to compute (PSA_ALG_XXX value such that PSA_ALG_IS_CIPHER(alg) is true).

Return values

Encrypt a message using a symmetric cipher.

This function encrypts a message with a random IV (initialization vector). Use the multipart operation interface with a psa_cipher_operation_t object to provide other forms of IV.

Parameters

key Identifier of the key to use for the operation. It must allow the usage PSA_KEY_USAGE_ENCRYPT. alg The cipher algorithm to compute (PSA_ALG_XXX value such that PSA_ALG_IS_CIPHER(alg) is true). [in] input Buffer containing the message to encrypt. input_length Size of the input buffer in bytes. [out] output Buffer where the output is to be written. The output contains the IV followed by the ciphertext proper. output_size Size of the output buffer in bytes. [out] output_length On success, the number of bytes that make up the output.

Return values

Finish encrypting or decrypting a message in a cipher operation.

The application must call psa_cipher_encrypt_setup() or psa_cipher_decrypt_setup() before calling this function. The choice of setup function determines whether this function encrypts or decrypts its input.

This function finishes the encryption or decryption of the message formed by concatenating the inputs passed to preceding calls to psa_cipher_update().

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_cipher_abort().

Parameters

[in,out] operation Active cipher operation. [out] output Buffer where the output is to be written. output_size Size of the output buffer in bytes. [out] output_length On success, the number of bytes that make up the returned output.

Return values

Generate an IV for a symmetric encryption operation.

This function generates a random IV (initialization vector), nonce or initial counter value for the encryption operation as appropriate for the chosen algorithm, key type and key size.

The application must call psa_cipher_encrypt_setup() before calling this function.

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

Parameters

[in,out] operation Active cipher operation. [out] iv Buffer where the generated IV is to be written. iv_size Size of the iv buffer in bytes. [out] iv_length On success, the number of bytes of the generated IV.

Return values

Return an initial value for a cipher operation object.

Set the IV for a symmetric encryption or decryption operation.

This function sets the IV (initialization vector), nonce or initial counter value for the encryption or decryption operation.

The application must call psa_cipher_encrypt_setup() before calling this function.

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

Note

When encrypting, applications should use psa_cipher_generate_iv() instead of this function, unless implementing a protocol that requires a non-random IV.

Parameters

[in,out] operation Active cipher operation. [in] iv Buffer containing the IV to use. iv_length Size of the IV in bytes.

Return values

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

Before calling this function, you must: 1. Call either psa_cipher_encrypt_setup() or psa_cipher_decrypt_setup(). The choice of setup function determines whether this function encrypts or decrypts its input. 2. If the algorithm requires an IV, call psa_cipher_generate_iv() (recommended when encrypting) or psa_cipher_set_iv().

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

Parameters

[in,out] operation Active cipher operation. [in] input Buffer containing the message fragment to encrypt or decrypt. input_length Size of the input buffer in bytes. [out] output Buffer where the output is to be written. output_size Size of the output buffer in bytes. [out] output_length On success, the number of bytes that make up the returned output.

Return values

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