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Tamperproofing is a methodology used to hinder, deter or detect unauthorised access to a device or circumvention of a security system. Since any device or system can be foiled by a person with sufficient knowledge, equipment, and time, the term "tamperproof" is a misnomer unless some limitations on the tampering party's resources is explicit or assumed.
Tamper resistance is resistance to intentional malfunction or sabotage by either the normal users of a product, package, or system or others with physical access to it.
Tamper resistance ranges from simple features like screws with special drives and tamper-evident seals to more complex devices that render themselves inoperable or encrypt all data transmissions between individual chips, use of materials needing special tools and knowledge. Tamper-resistant devices or features are common on packages to deter package or product tampering or enable its detection.
Anti-tamper devices have one or more components: tamper resistance, tamper detection, tamper response, and tamper evidence. [1] In some applications, devices are only tamper-evident rather than tamper-resistant.
Tampering involves the deliberate altering or adulteration of a product, package, or system. Solutions may involve all phases of product production, packaging, distribution, logistics, sale, and use. No single solution can be considered as "tamper-proof". Often multiple levels of security need to be addressed to reduce the risk of tampering. [2]
Some considerations might include:
Some devices contain non-standard screws or bolts in an attempt to deter access. Examples are telephone switching cabinets (which have triangular bolt heads that a hex socket fits), or bolts with 5-sided heads used to secure doors to outdoor electrical distribution transformers. A standard Torx screw head can be made in a tamper-resistant form with a pin in the center, which excludes standard Torx drivers. Various other security screw heads have been devised to discourage casual access to the interior of such devices as consumer electronics.
This style of tamper resistance is most commonly found in burglar alarms. Most trip devices (e.g. pressure pads, passive infrared sensors (motion detectors), door switches) use two signal wires that, depending on configuration, are normally open or normally closed. The sensors sometimes need power, so to simplify cable runs, multi-core cable is used. While 4 cores is normally enough for devices that require power (leaving two spare for those that don't), cable with additional cores can be used. These additional cores can be wired into a special so-called "tamper circuit" in the alarm system. Tamper circuits are monitored by the system to give an alarm if a disturbance to devices or wiring is detected. Enclosures for devices and control panels may be fitted with anti-tamper switches. Would-be intruders run the risk of triggering the alarm by attempting to circumvent a given device.
Sensors such as movement detectors, tilt detectors, air-pressure sensors, light sensors, etc., which might be employed in some burglar alarms, might also be used in a bomb to hinder defusing.
Nearly all appliances and accessories can only be opened with the use of a tool. This is intended to prevent casual or accidental access to energized or hot parts, or damage to the equipment. Manufacturers may use tamper-resistant screws, which cannot be unfastened with common tools. Tamper-resistant screws are used on electrical fittings in many public buildings to reduce tampering or vandalism that may cause a danger to others.
A user who breaks equipment by modifying it in a way not intended by the manufacturer might deny they did it, in order to claim the warranty or (mainly in the case of PCs) call the helpdesk for help in fixing it. Tamper-evident seals may be enough to deal with this. However, they cannot easily be checked remotely, and many countries have statutory warranty terms that mean manufacturers may still have to service the equipment. Tamper proof screws will stop most casual users from tampering in the first place. In the US, the Magnuson-Moss Warranty Act prevents manufacturers from voiding warranties solely due to tampering.[ citation needed ] A warranty may be dishonored only if the tampering actually affected the part that has failed, and could have caused the failure.
Tamper-resistant microprocessors are used to store and process private or sensitive information, such as private keys or electronic money credit. To prevent an attacker from retrieving or modifying the information, the chips are designed so that the information is not accessible through external means and can be accessed only by the embedded software, which should contain the appropriate security measures.
Examples of tamper-resistant chips include all secure cryptoprocessors, such as the IBM 4758 and chips used in smartcards, as well as the Clipper chip.
It has been argued that it is very difficult to make simple electronic devices secure against tampering, because numerous attacks are possible, including:
Tamper-resistant chips may be designed to zeroise their sensitive data (especially cryptographic keys) if they detect penetration of their security encapsulation or out-of-specification environmental parameters. A chip may even be rated for "cold zeroisation", the ability to zeroise itself even after its power supply has been crippled. In addition, the custom-made encapsulation methods used for chips used in some cryptographic products may be designed in such a manner that they are internally pre-stressed, so the chip will fracture if interfered with.[ citation needed ]
Nevertheless, the fact that an attacker may have the device in their possession for as long as they like, and perhaps obtain numerous other samples for testing and practice, means that it is impossible to totally eliminate tampering by a sufficiently motivated opponent. Because of this, one of the most important elements in protecting a system is overall system design. In particular, tamper-resistant systems should "fail gracefully" by ensuring that compromise of one device does not compromise the entire system. In this manner, the attacker can be practically restricted to attacks that cost more than the expected return from compromising a single device. Since the most sophisticated attacks have been estimated to cost several hundred thousand dollars to carry out, carefully designed systems may be invulnerable in practice.
In the United States, purchasing specifications require anti-tamper (AT) features on military electronic systems. [1]
Tamper resistance finds application in smart cards, set-top boxes and other devices that use digital rights management (DRM). In this case, the issue is not about stopping the user from breaking the equipment or hurting themselves, but about either stopping them from extracting codes, or acquiring and saving the decoded bitstream. This is usually done by having many subsystem features buried within each chip (so that internal signals and states are inaccessible) and by making sure the buses between chips are encrypted. [ citation needed ]
DRM mechanisms also use certificates and asymmetric key cryptography in many cases. In all such cases, tamper resistance means not allowing the device user access to the valid device certificates or public-private keys of the device. The process of making software robust against tampering attacks is referred to as "software anti-tamper".
Tamper resistance is sometimes needed in packaging, for example:
Resistance to tampering can be built in or added to packaging. [3] Examples include:
Software is also said to be tamper-resistant when it contains measures to make reverse engineering harder, or to prevent a user from modifying it against the manufacturer's wishes (such as removing a restriction on how it can be used). One commonly-used method is code obfuscation.
However, effective tamper resistance in software is much harder than in hardware, as the software environment can be manipulated to near-arbitrary extent by the use of emulation.
If implemented, trusted computing would make software tampering of protected programs at least as difficult as hardware tampering, as the user would have to hack the trust chip to give false certifications in order to bypass remote attestation and sealed storage. However, the current specification makes it clear that the chip is not expected to be tamper-proof against any reasonably sophisticated physical attack; [4] that is, it is not intended to be as secure as a tamper-resistant device.
That has the side effect that software maintenance gets more complex because software updates need to be validated, and errors in the upgrade process may lead to a false-positive triggering of the protection mechanism.
Authentication is the act of proving an assertion, such as the identity of a computer system user. In contrast with identification, the act of indicating a person or thing's identity, authentication is the process of verifying that identity. It might involve validating personal identity documents, verifying the authenticity of a website with a digital certificate, determining the age of an artifact by carbon dating, or ensuring that a product or document is not counterfeit.
Trusted Computing (TC) is a technology developed and promoted by the Trusted Computing Group. The term is taken from the field of trusted systems and has a specialized meaning that is distinct from the field of confidential computing. With Trusted Computing, the computer will consistently behave in expected ways, and those behaviors will be enforced by computer hardware and software. Enforcing this behavior is achieved by loading the hardware with a unique encryption key that is inaccessible to the rest of the system and the owner.
Physical security describes security measures that are designed to deny unauthorized access to facilities, equipment, and resources and to protect personnel and property from damage or harm. Physical security involves the use of multiple layers of interdependent systems that can include CCTV surveillance, security guards, protective barriers, locks, access control, perimeter intrusion detection, deterrent systems, fire protection, and other systems designed to protect persons and property.
A secure cryptoprocessor is a dedicated computer-on-a-chip or microprocessor for carrying out cryptographic operations, embedded in a packaging with multiple physical security measures, which give it a degree of tamper resistance. Unlike cryptographic processors that output decrypted data onto a bus in a secure environment, a secure cryptoprocessor does not output decrypted data or decrypted program instructions in an environment where security cannot always be maintained.
SCADA is a control system architecture comprising computers, networked data communications and graphical user interfaces for high-level supervision of machines and processes. It also covers sensors and other devices, such as programmable logic controllers, which interface with process plant or machinery.
A screw cap or closure is a common type of closure for bottles, jars, and tubes.
A software protection dongle is an electronic copy protection and content protection device. When connected to a computer or other electronics, they unlock software functionality or decode content. The hardware key is programmed with a product key or other cryptographic protection mechanism and functions via an electrical connector to an external bus of the computer or appliance.
An over-the-air update, also known as over-the-air programming, is an update to an embedded system that is delivered through a wireless network, such as Wi-Fi or a cellular network. These embedded systems include mobile phones, tablets, set-top boxes, cars and telecommunications equipment. OTA updates for cars and internet of things devices can also be called firmware over-the-air (FOTA). Various components may be updated OTA, including the device's operating system, applications, configuration settings, or parameters like encryption keys.
A security token is a peripheral device used to gain access to an electronically restricted resource. The token is used in addition to, or in place of, a password. Examples of security tokens include wireless key cards used to open locked doors, a banking token used as a digital authenticator for signing in to online banking, or signing transactions such as wire transfers.
A closure is a device used to close or seal a container such as a bottle, jug, jar, tube, or can. A closure may be a cap, cover, lid, plug, liner, or the like. The part of the container to which the closure is applied is called the finish.
Tamper-evident describes a device or process that makes unauthorized access to the protected object easily detected. Seals, markings, or other techniques may be tamper indicating.
Building automation (BAS), also known as building management system (BMS) or building energy management system (BEMS), is the automatic centralized control of a building's HVAC, electrical, lighting, shading, access control, security systems, and other interrelated systems. Some objectives of building automation are improved occupant comfort, efficient operation of building systems, reduction in energy consumption, reduced operating and maintaining costs and increased security.
Trusted Platform Module (TPM) is an international standard for a secure cryptoprocessor, a dedicated microcontroller designed to secure hardware through integrated cryptographic keys. The term can also refer to a chip conforming to the standard ISO/IEC 11889. Common uses are to verify platform integrity, and to store disk encryption keys.
A hardware security module (HSM) is a physical computing device that safeguards and manages secrets, performs encryption and decryption functions for digital signatures, strong authentication and other cryptographic functions. These modules traditionally come in the form of a plug-in card or an external device that attaches directly to a computer or network server. A hardware security module contains one or more secure cryptoprocessor chips.
Vandal-resistant switches are electrical switches designed to be installed in a location and application where they may be subject to abuse and attempts to damage them, as in the case of pedestrian crossing switches. Vandal-resistant switches located on devices that are outdoors must be able to withstand extreme temperatures, dust, rain, snow, and ice. Many vandal-resistant switches are intended to be operated by the general public, and must withstand heavy use and even abuse, such as attempts to damage the switch with metal tools. These switches must also resist dirt and moisture.
A tamper-evident band or security ring serves as a tamper resistant or tamper evident function to a screw cap, lid, or closure. The term tamper-proof is sometimes used but is considered a misnomer given that pilfering is still technically possible.
A Secure End Node is a trusted, individual computer that temporarily becomes part of a trusted, sensitive, well-managed network and later connects to many other (un)trusted networks/clouds. SEN's cannot communicate good or evil data between the various networks. SENs often connect through an untrusted medium and thus require a secure connection and strong authentication. The amount of trust required is commensurate with the risk of piracy, tampering, and reverse engineering. An essential characteristic of SENs is they cannot persist information as they change between networks.
A trusted execution environment (TEE) is a secure area of a main processor. It helps the code and data loaded inside it be protected with respect to confidentiality and integrity. Data confidentiality prevents unauthorized entities from outside the TEE from reading data, while code integrity prevents code in the TEE from being replaced or modified by unauthorized entities, which may also be the computer owner itself as in certain DRM schemes described in Intel SGX.
Security tape is a type of adhesive tape used to help reduce shipping losses due to pilfering and theft. It helps reduce tampering or product adulteration. It is often a pressure-sensitive tape or label with special tamper-resistant or tamper-evident features. It can be used as a security seal in addition to a container closure or can be used as a security label. They are sometimes used as or with authentication products and as an anti-pilferage seal.
A secure element (SE) is a secure operating system (OS) in a tamper-resistant processor chip or secure component. It can protect assets (root of trust, sensitive data, keys, certificates, applications) against high-level software and hardware attacks. Applications that process this sensitive data on an SE are isolated and so operate within a controlled environment not affected by software (including possible malware) found elsewhere on the OS.