Awide range of devices are designed to handle, convey and store sensitive information that requires varying degrees of security from protecting low level administrative to classified and top secret information. In addition, the information and data can reside in an equally wide range of locations and environments from protected and guarded facilities to unsecure desks and offices and over a wide range of environmental conditions including temperature, humidity, shock and vibration.

Figure 1. LDS security circuit integrated with enclosure.
The National Institute of Standards and Technology (NIST), in conjunction with industry, developed security requirements for cryptographic modules to protect sensitive information on computer and telecommunications systems. The standards are known as The Federal Information Processing Standard (FIPS) Publication 140-2.1

FIPS 140-2 provides four levels of increasing security to allow the appropriate level of security to be applied depending on the sensitivity of the information and the use environment.

Security Level 1 provides the lowest level of security for a cryptographic module and includes at least one approved algorithm or security function but requires no specific physical security mechanisms.

Security Level 2 adds the requirement for physical security mechanisms such as tamper-evident seals, coatings, or pick resistant locks on removable covers and doors in addition to the requirements of Security Level 1.

Security Level 3, in addition to the tamper-evident physical security mechanisms required in Security Level 2, seeks to prevent intrusion and access to critical security parameters (CSP) incorporated within the cryptographic module by means such as reinforced enclosures, tamper detection, and response circuitry that zeros all plain text CSPs when the covers/doors are tampered with or opened.

Security Level 4 provides for the highest level of security requiring physical security mechanisms to completely incase the cryptographic module, detect and respond to unauthorized attempts of physical access that may come at the cryptographic module from any direction by zeroing all plain text CSPs. Level 4 devices must also protect the cryptographic module from compromise due to environmental conditions and changes outside of the modules normal operating values for voltage and temperature. The cryptographic module must contain features to detect environmental fluctuations outside the design range and zero all CPSs should those parameters be exceeded or must undergo environmental failure testing to validate the module will not be affected by outside fluctuations beyond its normal operating range.

Depending on the required level of security and the operating environment, designers must consider both electronic and physical barrier protection against intrusion and environmental conditions as part of a comprehensive data protection strategy.

Package Protection

Figure 2. LDS Security Shield Circuitry on the inside of a component protection cover.
Package or envelope protection is a first line of defense in protecting sensitive data and electronic components from attackers trying to access content. Tampering techniques are classified into four major techniques.

Microprobing, where attempts are made to access the chip or bus circuits by physical connection or contact. Microprobing is an invasive attack. • Eavesdropping, a technique used to monitor the analog characteristics of electromagnetic radiation produced by processors and components. • Software attacks, that attempt to exploit flaws in algorithms and protocols through communications interfaces. • Fault generation seeks to create an abnormal environmental condition that will cause a malfunction in protected components.

Eavesdropping, software attacks and fault generation are non-invasive attacks, where once the vulnerability is uncovered it may rapidly be used against other devices of the same kind.

Constructing a non-invasive attack requires specific knowledge of the device’s construction and is made significantly easier if known. Invasive microprobing, on the other hand, does not require any advance knowledge of the device and attacks often start with attempts to reverse-engineer security elements and then use those results to develop faster, lower cost methods of non-invasive techniques.2