Age verification system
An age verification system, also known as an age gate, is a technical protection measure used to restrict access to digital content to those to are appropriately-aged. These systems are used primarily to restrict access to content classified (either voluntarily or by local laws) as being inappropriate for users under a specific age, such as alcohol and tobacco advertising, internet pornography or other forms of adult-oriented content, video games with objectionable content, or to remain in compliance with online privacy laws that regulate the collection of personal information from children (such as COPPA in the United States).
In the United Kingdom, the Digital Economy Act 2017 will require websites publishing porn commercially to employ an age verification system, with the British Board of Film Classification tasked in enforcing the provisions. The implementation of this rule was delayed indefinitely, in order to allow the BBFC to draft and receive approval for official guidelines regarding the age verification requirements.
The most basic form of age verification is to ask users to input their date of birth on a form. However, this depends on an honor system that assumes the validity of the end user (which can be a minor who fraudulently inserts a valid date that meets the age criteria, rather than their own), and has thus been described as ineffective.
Credit card verification
More sophisticated age verification systems require users to provide credit card information. However, this depends on an assumption that the vast majority of credit card holders are adults, because U.S. credit card companies did not originally issue cards to minors. Additionally, a minor may still attempt to obtain their parent's credit card information, or defraud users into divulging their credit card number to an individual to use for their own purposes, defeating the stated purpose of the system.
In 2005, Salvatore LoCascio plead guilty to charges of credit card fraud; one of his schemes had involved using credit card-based age verification systems to charge users for "free" tours of adult entertainment websites.
MindGeek, a major operator of porn websites, operates an age verification provider known as AgeID. Active in Germany since 2015, it uses third-party providers to authenticate the user's age, and a single sign-on model that allows the verified identity to be shared across any participating website.
In the United Kingdom, in response to concerns surrounding the data privacy of online age verification systems (which could be subject to mass processing by firms such as MindGeek, also acknowledging the implementation of the European Union's General Data Protection Regulation), the BBFC suggested that a system of gift card-like vouchers, purchased in person with ages checked by the retailer (similarly to other typically age-restricted purchases) would provide a more anonymous and secure solution to age verification 
The adult-oriented video game franchise Leisure Suit Larry took a different approach, requiring players to answer trivia questions that, in the opinion of franchise creator Al Lowe, a child presumably would not know the answer to.
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