CryptoCC26XX_AESCCM_Transaction Struct Reference

CryptoCC26XX AES-CCM Transaction. More...

#include <CryptoCC26XX.h>

Data Fields
CryptoCC26XX_Operation	opType
CryptoCC26XX_Mode	mode
uint8_t	keyIndex
uint8_t	authLength
char *	nonce
char *	msgIn
char *	header
void *	msgOut
uint8_t	fieldLength
uint16_t	msgInLength
uint16_t	headerLength

Detailed Description

CryptoCC26XX AES-CCM Transaction.

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. AES-CCM combines CBC-MAC with an AES block cipher.

AES-CCM encryption has the following inputs and outputs:

AES-CCM input and output parameters

Encryption	Decryption
Input
Shared AES key	Shared AES key
Nonce	Nonce
Cleartext	Ciphertext (encrypted cleartext + MAC)
AAD (optional)	AAD (optional)
Output
Ciphertext (encrypted cleartext + MAC)	Cleartext

The AES key is a shared secret between the two parties and has a length of 128 Bit. The key is stored in the dedicated RAM of the AES hardware unit before the crypto operation.

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 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 for transport layer security.

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.

AES-CCM works in both ways: encryption and decryption. When a message is decrypted, then ciphertext, AAD and nonce are used as inputs while the output comprises the cleartext only. The decryption operation is successful, when the received ciphertext, the nonce and the AAD can reproduce the containing MAC.

The CryptoCC26XX_AESCCM_Transaction structure defines all necessary parameters for a AES-CCM transaction.

Field Documentation

CryptoCC26XX_Operation CryptoCC26XX_AESCCM_Transaction::opType

The type of the crypto operation

CryptoCC26XX_Mode CryptoCC26XX_AESCCM_Transaction::mode

The mode of current transaction. Set by transact function.

uint8_t CryptoCC26XX_AESCCM_Transaction::keyIndex

The key store index to be used

uint8_t CryptoCC26XX_AESCCM_Transaction::authLength

Is the the length of the authentication field 0, 2, 4, 6, 8, 10, 12, 14 or 16 octets.

char* CryptoCC26XX_AESCCM_Transaction::nonce

A pointer to 13-byte or 12-byte Nonce.

char* CryptoCC26XX_AESCCM_Transaction::msgIn

• Encryption: A pointer to the octet string input message and after the transaction, the location of the encrypted cleartext. The cleatext is encrypted in place.
• Decryption: A pointer to the encrypted ciphertext composed of the encrypted cleartext concatenated with the encrypted message authentication code.

char* CryptoCC26XX_AESCCM_Transaction::header

The Additional Authentication Data (AAD). This header is authenticated but not encrypted.

void* CryptoCC26XX_AESCCM_Transaction::msgOut

A pointer to the encrypted CBC-MAC

uint8_t CryptoCC26XX_AESCCM_Transaction::fieldLength

Encoded length of the nonce.

fieldLength	nonce length
2	13 byte nonce
3	12 byte nonce

uint16_t CryptoCC26XX_AESCCM_Transaction::msgInLength

• Encryption: The length of the cleartext.
• Decryption: The length of the ciphertext.

uint16_t CryptoCC26XX_AESCCM_Transaction::headerLength

The length of the header in octets

---

The documentation for this struct was generated from the following file:

• CryptoCC26XX.h