Tamper evident

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.

Tampering involves the deliberate altering or adulteration of information, a product, a package, or system. Solutions may involve all phases of product production, 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. Some considerations might include:

Tamper-evident designs have been a feature of letters since ancient times, often using wax, clay, or metal seals to signify that the letter had not been opened since it was written. Roman signet rings for example, were unique to the person who owned them, and the ring was pressed into the hot wax seal forming a signature which could not be easily duplicated by somebody attempting to re-seal the letter.

Similar practices continue today, from examples such as envelopes to carefully designed packaging for payslips. In modern contract law, it is common to see each page of a contract individually initialled and numbered, so that any addition or removal of pages can be detected. Meanwhile, most checks have a variety of features to defeat both tampering and duplication (these are often listed on the back of the check).

Technicians at the National Security Agency developed anti-tamper holograph and prism labels that are difficult to duplicate.

Security seals are commonly employed on devices like electronic voting machines in an attempt to detect tampering. However, testing by Argonne National Laboratory and others demonstrates that existing seals can usually be quickly defeated by a trained person using low-tech methods. They offer ideas on countermeasures, and are exploring the promising option of "anti-evidence" seals.

Tamper-evident design is perhaps most visible in the process of product packaging and labelling, where it can be vital to know that the product has not been altered since it left the manufacturer.

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Wikipedia