The truth behind the secret archives stems from a mistranslation of Latin. The actual name of the Vatican archives is Archivum Secretum Apostolicum Vaticanum. 'Secretum' in Latin does not mean 'secret' as some may suppose. It is more accurately translated to mean 'personal' or 'private'.
The archives are made up of the private letters and historic records of past popes over the past four centuries. The archives were established by Pope Paul V. The Pope had a sense of the historic importance of papal correspondence and knew that such documents should be preserved. However, the 17th century was firm in the mentality that common people should not be privy to words exchanged by kings and popes. So the archives were kept under lock and key.
It was not until 1881 that Pope Leo XIII allowed researchers to view some of the archive's contents. However, it was not a simple matter for one to view the documents and the procedure has not changed much over the last 200 years. First of all, journalists, students, and amateur historians are not given access. Once an interested party has proven that he or she is a serious enough scholar, credentials are granted that must be renewed every six months. To enter the archives, "scholars enter through the Porta Sant'Anna, pass Swiss Guards, walk through the Cortile del Belvedere, and present credentials"
Once admitted, scholars must request which specific documents they wish to review. They are only allowed to request three per day. So instead of being able to browse the contents of the archive, they must select articles from catalogs in which items are handwritten in Italian or Latin. These catalogs are quite imposing considering that the archives contain "50 miles [80km] of shelving and documents dating back to the eighth century" (Keyser, 2015). "If in just a few minutes they realize that what they're seeking isn't in the requested folders, they're forced to pack up for the day - a challenge for scholars on a deadline or those who have traveled long distances" (O'Loughlin, 2014). Computers are allowed but not photography so scholars spend most of the sessions in reading rooms typing up notes.