MAX32600 User’s Guide
Introduction
2.8 Security Features
• 1/2 duty multiplexed with 1/2 bias voltages (COM [0:1])
• 1/3 duty multiplexed with 1/3 bias voltages (COM [0:2])
• 1/4 duty multiplexed with 1/3 bias voltages (COM [0:3])
Note
Since the voltages available for LCD drive are
V
LCD
,
V
LCD
×
2
3
,
V
LCD
×
1
3
, and
V
ADJ
, the
1
2
-bias mode (which requires an output level of
V
LCD
×
1
2
) will
require two of the LCD voltage output pins (V
LCD2
and V
LCD1
) to be shunted together externally.
2.8
Security Features
2.8.1
Trust Protection Unit (TPU)
The
MAX32600
includes several cryptographic and security peripherals which are grouped together to form the Trust Protection Unit, or TPU. The TPU architecture
includes cryptographic peripherals (such as the AES engine or the Micro MAA) as well as security features (such as the dynamic tamper sensor) which help to form
a secure cryptographic boundary for protecting critical user information within the device.
2.8.2
AES Cryptographic Engine
Another component found in the TPU is an Advanced Encryption Standard (AES) cryptographic engine. This cryptographic engine allows 256-bit AES encryption
and decryption operations to be performed in hardware without processor intervention.
The AES control register selects encryption or decryption mode, controls interrupt notification of the processor upon an operation completion, and selects whether
or not the key expansion (generation of first/last round key) is performed before the encryption or decryption operation begins. For multiple-block encryption or
decryption operations using a single key, the key expansion is performed on the first block only, allowing subsequent operations to complete more quickly by reusing
the previously generated round key information.
The working AES key, cryptographic working space, and input and output parameters (plaintext to ciphertext or vice versa) are stored in a dedicated internal AES
memory. This memory is automatically cleared (rapid zeroization) in the event of a tamper response.
2.8.3
Battery-Backed AES Secure Key Storage
The battery-backed (by the V
RTC
supply voltage) RTC module contains a dedicated set of registers which can be used to store a master AES key or other critical
data. This master AES key can be generated by the device using a PRNG random number sequence, and is stored in a dedicated location in the RTC register area
which will be automatically cleared (rapid zeroization) in the event of a tamper response.
This key is intended for use in encrypting other sensitive information that might be stored in other locations on the device (such as the main system SRAM or the
program flash memory) that will not be automatically wiped in the event of a tamper response. However, if this sensitive information has been encrypted before
Rev.1.3 April 2015
Maxim Integrated
Page 21