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 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: Identify who a potential tamperer might be and what level of knowledge, materials, tools, etc. might they have. Identify all feasible methods of unauthorized access into a product, package, or system. In addition to the primary means of entry, also consider secondary or "back door" methods. Control or limit access to products or systems of interest. Improve the tamper resistance by making tampering more difficult, time-consuming, etc. Add tamper-evident features to help indicate the existence of tampering. Educate people to watch for evidence of tampering. Length of time available for tampering. Particularly in transit, anyone intending to tamper with tamper-evident-protected goods, valuables, cash and confidential documents generally only has a window of opportunity of a few minutes before discovery is likely. This makes it both difficult and unlikely that they will have time to open the packaging, examine or remove the items, and restore the packaging to its original untampered condition. Seals and signatures 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. Ancient 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. Letterlocking, including a type called spiral locking, used intricate folding, slitting, and weaving to create the result that any opening attempt would be evident via rips and tears in addition to the breaking of the wax seals. 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