Secure 2 click carries the ATAES132A, a cryptographic coprocessor with secure hardware-based key storage from Microchip. The click is designed to run on either 3.3V or 5V power supply. Secure 2 click communicates with the target microcontroller over SPI and I2C interface, with additional functionality provided by the INT pin on the mikroBUS??? line.

ATAES132A features

The ATAES132A is a high-security, Serial Electrically-Erasable and Programmable Read-Only Memory (Serial EEPROM) providing both authentication and confidential nonvolatile data storage capabilities. Access restrictions for the 16 user zones are independently configured, and any key can be used with any zone. In addition, keys can be used for standalone authentication.

The AES-128 cryptographic engine operates in AES-CCM mode to provide authentication, stored data encryption/decryption, and Message Authentication Codes. Data encryption/decryption can be performed for internally stored data or for small external data packets, depending upon the configuration. Data encrypted by one ATAES132A device can be decrypted by another, and vice versa.

Specifications

Pinout diagram

This table shows how the pinout on Secure 2 click corresponds to the pinout on the mikroBUS??? socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
	NC	1	AN	PWM	16	NC
	NC	2	RST	INT	15	AUTH	Auth signaling
Chip select	CS	3	CS	TX	14	NC
SPI clock	SCK	4	SCK	RX	13	NC
Slave data out for SPI	SDO	5	MISO	SCL	12	SCL	I2C clock
Slave data in for SPI	SDI	6	MOSI	SDA	11	SDA	I2C data
Power supply	+3.3V	7	3.3V	5V	10	+5V	Power supply
Ground	GND	8	GND	GND	9	GND	Ground

Programming

Code examples for Secure 2 click, written for MikroElektronika hardware and compilers are available on Libstock.

Code snippet

The following code snippet shows functions that will lock the configuration zone of the device and then output a generated random number.

01 //Configuration zone locking
02     if (aes132m_execute(AES132_LOCK, 0x02, 0x0000, 0x0000,
03                         0, 0, 0, 0, 0, 0, 0, 0, txBuffer, rxBuffer)
04                         == AES132_FUNCTION_RETCODE_SUCCESS)
05     {
06         LOG( "rnrn Configuration zone locked! " );
07     }
08     else
09     {
10         LOG( "rnrn Configuration zone locking failed" );
11         LOG( " or it is already locked." );
12     }
13     memset (txBuffer, 0, 84);
14     memset (rxBuffer, 0, 36);
15 /*
16     Fourth test - Random number generator
17     Will only return 0xA5 unless config zone is locked first.
18 */
19     if (aes132m_execute(AES132_RANDOM, 0x00, 0x0000, 0x0000,
20                         0, 0, 0, 0, 0, 0, 0, 0, txBuffer, rxBuffer)
21                         == AES132_FUNCTION_RETCODE_SUCCESS)
22     {
23         LOG( "rnrn Generated random number: " );
24         outputHex (&rxBuffer[2], 16);
25     }
26     else  LOG( "rnrn Random number generation failed..." );
27 
28    memset (txBuffer, 0, 84);
29     memset (rxBuffer, 0, 36);