Data Structures | Macros | Typedefs | Enumerations | Functions | Variables
AESCCM.h File Reference

Detailed Description

AESCCM driver header.

============================================================================

Warning
This is a beta API. It may change in future releases.

Overview

The Counter with CBC-MAC (CCM) mode of operation is a generic authenticated encryption block cipher mode. It can be used with any 128-bit block cipher. AESCCM combines CBC-MAC with an AES block cipher in CTR mode of operation.

This combination of block cipher modes enables CCM to encrypt messages of any length and not only multiples of the block cipher block size.

AESCCM encryption has the following inputs and outputs:

AES-CCM input and output parameters
EncryptionDecryption
Input
Shared AES keyShared AES key
NonceNonce
CleartextCiphertext (encrypted plaintext + MAC)
AAD (optional)AAD (optional)
Output
Ciphertext (encrypted plaintext + MAC)Cleartext

The AES key is a shared secret between the two parties and has a length between 128 and 256 bits.

The nonce is generated by the party performing the authenticated encryption operation. Within the scope of any authenticated encryption key, the nonce value must be unique. That is, the set of nonce values used with any given key must not contain any duplicate values. Using the same nonce for two different messages encrypted with the same key destroys the security properties.

The optional additional authentication data (AAD) is authenticated, but not encrypted. Thus, the AAD is not included in the AES-CCM output. It can be used to authenticate packet headers.

After the encryption operation, the ciphertext contains the encrypted data and the message authentication code (MAC). The MAC can be seen as an encrypted fingerprint of the message header and content.

Usage

Before starting a CCM operation

Before starting a CCM operation, the application must do the following:

Starting a CCM operation

There are two general ways to execute a CCM operation. In one call or multiple.

The AESCCM_oneStepEncrypt and AESCCM_oneStepDecrypt functions do a CCM operation in a single call. They will always be the most highly optimized routines with the least overhead and the fastest runtime. However, they require all AAD and plaintext or ciphertext data to be available to the function at the start of the call. When trying to operate on data that is too large to fit into available memory, partial processing would be more advisable. All devices support single call operations. When performing a decryption operation with AESCCM_oneStepDecrypt(), the MAC is automatically verified when using AESCCM_RETURN_BEHAVIOR_BLOCKING or AESCCM_RETURN_BEHAVIOR_POLLING. When using AESCCM_RETURN_BEHAVIOR_CALLBACK however, the application's registered callback function must call AESCCM_verifyMac() itself to ensure that the computed and transmitted MACs match.

After the CCM operation completes

After the CCM operation completes, the application should either start another operation or close the driver by calling AESCCM_close()

AESCCM Driver Configuration

In order to use the AESCCM APIs, the application is required to provide device-specific AESCCM configuration in the Board.c file. The AESCCM driver interface defines a configuration data structure:

typedef struct AESCCM_Config_ {
void *object;
void const *hwAttrs;

The application must declare an array of AESCCM_Config elements, named AESCCM_config[]. Each element of AESCCM_config[] must be populated with pointers to a device specific AESCCM driver implementation's driver object and hardware attributes. The hardware attributes define properties such as the AESCCM peripheral's base address. Each element in AESCCM_config[] corresponds to an AESCCM instance and none of the elements should have NULL pointers. There is no correlation between the index and the peripheral designation (such as AESCCM0 or AESCCM1). For example, it is possible to use AESCCM_config[0] for AESCCM1. Multiple drivers and driver instances may all access the same underlying hardware. This is transparent to the application. Mutual exclusion is performed automatically by the drivers as necessary.

Because the AESCCM configuration is very device dependent, you will need to check the doxygen for the device specific AESCCM implementation. There you will find a description of the AESCCM hardware attributes. Please also refer to the Board.c file of any of your examples to see the AESCCM configuration.

AESCCM Parameters

The AESCCM_Params structure is passed to the AESCCM_open() call. If NULL is passed for the parameters, AESCCM_open() uses default parameters. A AESCCM_Params structure is initialized with default values by passing it to AESCCM_Params_init(). Some of the AESCCM parameters are described below. To see brief descriptions of all the parameters, see AESCCM_Params.

AESCCM Return Behavior

The AESCCM driver supports three return behaviors when processing data: blocking, polling, and callback. The return behavior is determined by the returnBehavior parameter in the AESCCM_Params data structure. The AESCCM driver defaults to blocking mode, if the application does not set it. Once an AESCCM driver is opened, the only way to change the return behavior is to close and re-open the AESCCM instance with the new return behavior.

In blocking mode, a task's code execution is blocked until an AESCCM operation has completed. This ensures that only one AESCCM operation operates at a given time. Other tasks requesting AESCCM operations while a operation is currently taking place are also placed into a blocked state. AESCCM operations are executed in the order in which they were received. In blocking mode, you cannot perform AESCCM operations in the context of a software or hardware ISR.

In callback mode, an AESCCM operation functions asynchronously, which means that it does not block code execution. After an AESCCM operation has been completed, the AESCCM driver calls a user-provided hook function. Callback mode is supported in the task, SWI, and HWI execution context, However, if an AESCCM operation is requested while a operation is taking place, the call returns an error code.

In polling mode, an AESCCM operation behaves the almost the same way as in blocking mode. Instead of pending on a semaphore and letting other scheduled tasks run, the application task, SWI, or HWI continuously polls a flag until the operation completes. If an AESCCM operation is requested while a operation is taking place, the call returns an error code. When starting an AESCCM operation in polling mode from HWI or SWI context, the AESCCM HWI and SWI must be configured to have a higher priority to pre-empt the polling context.

Examples

### Single call CCM encryption + authentication with plaintext CryptoKey in blocking return mode #

#include <ti/drivers/types/cryptoKey/CryptoKey_Plaintext.h>
...
AESCCM_Handle handle;
CryptoKey cryptoKey;
int_fast16_t encryptionResult;
uint8_t nonce[] = "Thisisanonce";
uint8_t aad[] = "This string will be authenticated but not encrypted.";
uint8_t plaintext[] = "This string will be encrypted and authenticated.";
uint8_t mac[16];
uint8_t ciphertext[sizeof(plaintext)];
uint8_t keyingMaterial[32] = {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E, 0x1F}
handle = AESCCM_open(0, NULL);
if (handle == NULL) {
// handle error
}
CryptoKeyPlaintext_initKey(&cryptoKey, keyingMaterial, sizeof(keyingMaterial));
AESCCM_Operation operation;
AESCCM_Operation_init(&operation);
operation.key = &cryptoKey;
operation.aad = aad;
operation.aadLength = sizeof(aad);
operation.input = plaintext;
operation.output = ciphertext;
operation.inputLength = sizeof(plaintext);
operation.nonce = nonce;
operation.nonceLength = sizeof(nonce);
operation.mac = mac;
operation.macLength = sizeof(mac);
encryptionResult = AESCCM_oneStepEncrypt(handle, &operation);
if (encryptionResult != AESCCM_STATUS_SUCCESS) {
// handle error
}
AESCCM_close(handle);

Single call CCM decryption + verification with plaintext CryptoKey in callback return mode

...
// The following test vector is Packet Vector 1 from RFC 3610 of the IETF.
uint8_t nonce[] = {0x00, 0x00, 0x00, 0x03, 0x02, 0x01, 0x00, 0xA0,
0xA1, 0xA2, 0xA3, 0xA4, 0xA5};
uint8_t aad[] = {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07};
uint8_t mac[] = {0x17, 0xE8, 0xD1, 0x2C, 0xFD, 0xF9, 0x26, 0xE0};
uint8_t ciphertext[] = {0x58, 0x8C, 0x97, 0x9A, 0x61, 0xC6, 0x63, 0xD2,
0xF0, 0x66, 0xD0, 0xC2, 0xC0, 0xF9, 0x89, 0x80,
0x6D, 0x5F, 0x6B, 0x61, 0xDA, 0xC3, 0x84};
uint8_t keyingMaterial[] = {0xC0, 0xC1, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7,
0xC8, 0xC9, 0xCA, 0xCB, 0xCC, 0xCD, 0xCE, 0xCF};
uint8_t plaintext[sizeof(ciphertext)];
// The plaintext should be the following after the decryption operation:
// {0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
// 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
// 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x1E}
void ccmCallback(AESCCM_Handle handle,
int_fast16_t returnValue,
AESCCM_Operation *operation,
AESCCM_OperationType operationType) {
if (returnValue != AESCCM_STATUS_SUCCESS) {
// handle error
}
}
AESCCM_Operation operation;
void ccmStartFunction(void) {
AESCCM_Handle handle;
AESCCM_Params params;
CryptoKey cryptoKey;
int_fast16_t decryptionResult;
params.callbackFxn = ccmCallback;
handle = AESCCM_open(0, &params);
if (handle == NULL) {
// handle error
}
CryptoKeyPlaintext_initKey(&cryptoKey, keyingMaterial, sizeof(keyingMaterial));
AESCCM_Operation_init(&operation);
operation.key = &cryptoKey;
operation.aad = aad;
operation.aadLength = sizeof(aad);
operation.input = plaintext;
operation.output = ciphertext;
operation.inputLength = sizeof(plaintext);
operation.nonce = nonce;
operation.nonceLength = sizeof(nonce);
operation.mac = mac;
operation.macLength = sizeof(mac);
decryptionResult = AESCCM_oneStepDecrypt(handle, &operation);
if (decryptionResult != AESCCM_STATUS_SUCCESS) {
// handle error
}
// do other things while CCM operation completes in the background
}
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <ti/drivers/cryptoutils/cryptokey/CryptoKey.h>

Go to the source code of this file.

Data Structures

struct  AESCCM_Operation_
 Struct containing the parameters required for encrypting/decrypting and authenticating/verifying a message. More...
 
struct  AESCCM_Config_
 AESCCM Global configuration. More...
 
struct  AESCCM_Params_
 CCM Parameters. More...
 

Macros

#define AESCCM_CMD_RESERVED   (32)
 
#define AESCCM_STATUS_RESERVED   (-32)
 
#define AESCCM_STATUS_SUCCESS   (0)
 Successful status code. More...
 
#define AESCCM_STATUS_ERROR   (-1)
 Generic error status code. More...
 
#define AESCCM_STATUS_UNDEFINEDCMD   (-2)
 An error status code returned by AESCCM_control() for undefined command codes. More...
 
#define AESCCM_STATUS_RESOURCE_UNAVAILABLE   (-3)
 An error status code returned if the hardware or software resource is currently unavailable. More...
 
#define AESCCM_STATUS_MAC_INVALID   (-4)
 An error status code returned if the MAC provided by the application for a decryption operation does not match the one calculated during the operation. More...
 

Typedefs

typedef struct AESCCM_Config_AESCCM_Handle
 A handle that is returned from an AESCCM_open() call. More...
 
typedef enum AESCCM_ReturnBehavior_ AESCCM_ReturnBehavior
 The way in which CCM function calls return after performing an encryption + authentication or decryption + verification operation. More...
 
typedef enum AESCCM_Mode_ AESCCM_Mode
 Enum for the direction of the CCM operation. More...
 
typedef struct AESCCM_Operation_ AESCCM_Operation
 Struct containing the parameters required for encrypting/decrypting and authenticating/verifying a message. More...
 
typedef enum AESCCM_OperationType_ AESCCM_OperationType
 Enum for the operation types supported by the driver. More...
 
typedef struct AESCCM_Config_ AESCCM_Config
 AESCCM Global configuration. More...
 
typedef void(* AESCCM_CallbackFxn) (AESCCM_Handle handle, int_fast16_t returnValue, AESCCM_Operation *operation, AESCCM_OperationType operationType)
 The definition of a callback function used by the AESCCM driver when used in AESCCM_RETURN_BEHAVIOR_CALLBACK. More...
 
typedef struct AESCCM_Params_ AESCCM_Params
 CCM Parameters. More...
 

Enumerations

enum  AESCCM_ReturnBehavior_ { AESCCM_RETURN_BEHAVIOR_CALLBACK = 1, AESCCM_RETURN_BEHAVIOR_BLOCKING = 2, AESCCM_RETURN_BEHAVIOR_POLLING = 4 }
 The way in which CCM function calls return after performing an encryption + authentication or decryption + verification operation. More...
 
enum  AESCCM_Mode_ { AESCCM_MODE_ENCRYPT = 1, AESCCM_MODE_DECRYPT = 2 }
 Enum for the direction of the CCM operation. More...
 
enum  AESCCM_OperationType_ { AESCCM_OPERATION_TYPE_ENCRYPT = 1, AESCCM_OPERATION_TYPE_DECRYPT = 2 }
 Enum for the operation types supported by the driver. More...
 

Functions

void AESCCM_init (void)
 This function initializes the CCM module. More...
 
void AESCCM_Params_init (AESCCM_Params *params)
 Function to initialize the AESCCM_Params struct to its defaults. More...
 
AESCCM_Handle AESCCM_open (uint_least8_t index, AESCCM_Params *params)
 This function opens a given CCM peripheral. More...
 
void AESCCM_close (AESCCM_Handle handle)
 Function to close a CCM peripheral specified by the CCM handle. More...
 
int_fast16_t AESCCM_control (AESCCM_Handle handle, uint32_t cmd, void *args)
 Function performs implementation specific features on a given AESCCM_Handle. More...
 
void AESCCM_Operation_init (AESCCM_Operation *operationStruct)
 Function to initialize a AESCCM_Operation struct to its defaults. More...
 
int_fast16_t AESCCM_oneStepEncrypt (AESCCM_Handle handle, AESCCM_Operation *operationStruct)
 Function to perform an AESCCM encryption + authentication operation in one call. More...
 
int_fast16_t AESCCM_oneStepDecrypt (AESCCM_Handle handle, AESCCM_Operation *operationStruct)
 Function to perform an AESCCM decryption + verification operation in one call. More...
 

Variables

const AESCCM_Params AESCCM_defaultParams
 Default AESCCM_Params structure. More...
 

Typedef Documentation

§ AESCCM_Handle

typedef struct AESCCM_Config_* AESCCM_Handle

A handle that is returned from an AESCCM_open() call.

§ AESCCM_ReturnBehavior

The way in which CCM function calls return after performing an encryption + authentication or decryption + verification operation.

Not all CCM operations exhibit the specified return behavor. Functions that do not require significant computation and cannot offload that computation to a background thread behave like regular functions. Which functions exhibit the specfied return behavior is not implementation dependent. Specifically, a software-backed implementation run on the same CPU as the application will emulate the return behavior while not actually offloading the computation to the background thread.

AESCCM functions exhibiting the specified return behavior have restrictions on the context from which they may be called.

Task Hwi Swi
AESCCM_RETURN_BEHAVIOR_CALLBACK X X X
AESCCM_RETURN_BEHAVIOR_BLOCKING X
AESCCM_RETURN_BEHAVIOR_POLLING X X X

§ AESCCM_Mode

typedef enum AESCCM_Mode_ AESCCM_Mode

Enum for the direction of the CCM operation.

§ AESCCM_Operation

Struct containing the parameters required for encrypting/decrypting and authenticating/verifying a message.

§ AESCCM_OperationType

Enum for the operation types supported by the driver.

§ AESCCM_Config

typedef struct AESCCM_Config_ AESCCM_Config

AESCCM Global configuration.

The AESCCM_Config structure contains a set of pointers used to characterize the AESCCM driver implementation.

This structure needs to be defined before calling AESCCM_init() and it must not be changed thereafter.

See also
AESCCM_init()

§ AESCCM_CallbackFxn

typedef void(* AESCCM_CallbackFxn) (AESCCM_Handle handle, int_fast16_t returnValue, AESCCM_Operation *operation, AESCCM_OperationType operationType)

The definition of a callback function used by the AESCCM driver when used in AESCCM_RETURN_BEHAVIOR_CALLBACK.

Parameters
handleHandle of the client that started the CCM operation.
processedKeyThe CryptoKey that the CCM operation was performed with.

§ AESCCM_Params

typedef struct AESCCM_Params_ AESCCM_Params

CCM Parameters.

CCM Parameters are used to with the AESCCM_open() call. Default values for these parameters are set using AESCCM_Params_init().

See also
AESCCM_Params_init()

Enumeration Type Documentation

§ AESCCM_ReturnBehavior_

The way in which CCM function calls return after performing an encryption + authentication or decryption + verification operation.

Not all CCM operations exhibit the specified return behavor. Functions that do not require significant computation and cannot offload that computation to a background thread behave like regular functions. Which functions exhibit the specfied return behavior is not implementation dependent. Specifically, a software-backed implementation run on the same CPU as the application will emulate the return behavior while not actually offloading the computation to the background thread.

AESCCM functions exhibiting the specified return behavior have restrictions on the context from which they may be called.

Task Hwi Swi
AESCCM_RETURN_BEHAVIOR_CALLBACK X X X
AESCCM_RETURN_BEHAVIOR_BLOCKING X
AESCCM_RETURN_BEHAVIOR_POLLING X X X
Enumerator
AESCCM_RETURN_BEHAVIOR_CALLBACK 

The function call will return immediately while the CCM operation goes on in the background. The registered callback function is called after the operation completes. The context the callback function is called (task, HWI, SWI) is implementation-dependent.

AESCCM_RETURN_BEHAVIOR_BLOCKING 

The function call will block while CCM operation goes on in the background. CCM operation results are available after the function returns.

AESCCM_RETURN_BEHAVIOR_POLLING 

The function call will continuously poll a flag while CCM operation goes on in the background. CCM operation results are available after the function returns.

§ AESCCM_Mode_

Enum for the direction of the CCM operation.

Enumerator
AESCCM_MODE_ENCRYPT 
AESCCM_MODE_DECRYPT 

§ AESCCM_OperationType_

Enum for the operation types supported by the driver.

Enumerator
AESCCM_OPERATION_TYPE_ENCRYPT 
AESCCM_OPERATION_TYPE_DECRYPT 

Function Documentation

§ AESCCM_init()

void AESCCM_init ( void  )

This function initializes the CCM module.

Precondition
The AESCCM_config structure must exist and be persistent before this function can be called. This function must also be called before any other CCM driver APIs. This function call does not modify any peripheral registers.

§ AESCCM_Params_init()

void AESCCM_Params_init ( AESCCM_Params params)

Function to initialize the AESCCM_Params struct to its defaults.

Parameters
paramsAn pointer to AESCCM_Params structure for initialization

Defaults values are: returnBehavior = AESCCM_RETURN_BEHAVIOR_BLOCKING callbackFxn = NULL timeout = SemaphoreP_WAIT_FOREVER custom = NULL

§ AESCCM_open()

AESCCM_Handle AESCCM_open ( uint_least8_t  index,
AESCCM_Params params 
)

This function opens a given CCM peripheral.

Precondition
CCM controller has been initialized using AESCCM_init()
Parameters
indexLogical peripheral number for the CCM indexed into the AESCCM_config table
paramsPointer to an parameter block, if NULL it will use default values.
Returns
A AESCCM_Handle on success or a NULL on an error or if it has been opened already.
See also
AESCCM_init()
AESCCM_close()

§ AESCCM_close()

void AESCCM_close ( AESCCM_Handle  handle)

Function to close a CCM peripheral specified by the CCM handle.

Precondition
AESCCM_open() has to be called first.
Parameters
handleA CCM handle returned from AESCCM_open()
See also
AESCCM_open()

§ AESCCM_control()

int_fast16_t AESCCM_control ( AESCCM_Handle  handle,
uint32_t  cmd,
void *  args 
)

Function performs implementation specific features on a given AESCCM_Handle.

Commands for AESCCM_control can originate from AESCCM.h or from implementation specific AESCCM*.h (AESCCMCC26XX.h, AESCCMMSP432.h, etc.. ) files. While commands from AESCCM.h are API portable across driver implementations, not all implementations may support all these commands. Conversely, commands from driver implementation specific AESCCM*.h files add unique driver capabilities but are not API portable across all AESCCM driver implementations.

Commands supported by AESCCM.h follow an AESCCM_CMD_<cmd> naming convention.
Commands supported by AESCCM*.h follow an AESCCM*_CMD_<cmd> naming convention.
Each control command defines arg differently. The types of arg are documented with each command.

See AESCCM_control command codes for command codes.

See AESCCM_control return status codes for status codes.

Precondition
AESCCM_open() has to be called first.
Parameters
handleA AESCCM handle returned from AESCCM_open()
cmdAESCCM.h or AESCCM*.h commands.
argsAn optional R/W (read/write) command argument accompanied with cmd
Returns
Implementation specific return codes. Negative values indicate unsuccessful operations.
See also
AESCCM_open()

§ AESCCM_Operation_init()

void AESCCM_Operation_init ( AESCCM_Operation operationStruct)

Function to initialize a AESCCM_Operation struct to its defaults.

Parameters
operationStructAn pointer to AESCCM_Operation structure for initialization

Defaults values are all zeros.

§ AESCCM_oneStepEncrypt()

int_fast16_t AESCCM_oneStepEncrypt ( AESCCM_Handle  handle,
AESCCM_Operation operationStruct 
)

Function to perform an AESCCM encryption + authentication operation in one call.

Note
None of the buffers provided as arguments may be altered by the application during an ongoing operation. Doing so can yield corrupted ciphertext or incorrect authentication.
Precondition
AESCCM_open() and AESCCM_Operation_init() have to be called first.
Parameters
[in]handleA CCM handle returned from AESCCM_open()
[in]operationStructA pointer to a struct containing the parameters required to perform the operation.
Returns
A status code
See also
AESCCM_oneStepDecrypt()

§ AESCCM_oneStepDecrypt()

int_fast16_t AESCCM_oneStepDecrypt ( AESCCM_Handle  handle,
AESCCM_Operation operationStruct 
)

Function to perform an AESCCM decryption + verification operation in one call.

Note
None of the buffers provided as arguments may be altered by the application during an ongoing operation. Doing so can yield corrupted plaintext or incorrectly failed verification.
Precondition
AESCCM_open() and AESCCM_Operation_init() have to be called first.
Parameters
[in]handleA CCM handle returned from AESCCM_open()
[in]operationStructA pointer to a struct containing the parameters required to perform the operation.
Returns
A status code
See also
AESCCM_oneStepEncrypt()

Variable Documentation

§ AESCCM_defaultParams

const AESCCM_Params AESCCM_defaultParams

Default AESCCM_Params structure.

See also
AESCCM_Params_init()
Copyright 2017, Texas Instruments Incorporated