Certificates can, however, also be forged, and the authentication of these poses a problem.
The second type of authentication might involve comparing the quality and craftsmanship of an item, such as an expensive handbag, to genuine articles.
The third type of authentication could be the presence of a trademark on the item, which is a legally protected marking, or any other identifying feature which aids consumers in the identification of genuine brand-name goods.
Each authentication factor covers a range of elements used to authenticate or verify a person's identity prior to being granted access, approving a transaction request, signing a document or other work product, granting authority to others, and establishing a chain of authority.
Security research has determined that for a positive authentication, elements from at least two, and preferably all three, factors should be verified.
In computer science, verifying a person's identity is often required to allow access to confidential data or systems.
Authentication can be considered to be of three types: The first type of authentication is accepting proof of identity given by a credible person who has first-hand evidence that the identity is genuine.
These external records have their own problems of forgery and perjury, and are also vulnerable to being separated from the artifact and lost.
In computer science, a user can be given access to secure systems based on user credentials that imply authenticity.
When authentication is required of art or physical objects, this proof could be a friend, family member or colleague attesting to the item's provenance, perhaps by having witnessed the item in its creator's possession.
With autographed sports memorabilia, this could involve someone attesting that they witnessed the object being signed.
A vendor selling branded items implies authenticity, while he or she may not have evidence that every step in the supply chain was authenticated.