Cryptography is the practice and study of hiding information. In todays environment, cryptography is considered a branch of both mathematics and computer science, and is affiliated closely with information theory, computer security, and engineering. Cryptography is used in technologically advanced applications, including areas such as the security of ATM cards, computer passwords, and electronic commerce, which all depend on cryptography.
Cryptography has long been of interest to intelligence gathering and law enforcement agencies. There has historically been a history of controversial legal issues surrounding cryptography. In some countries the use of cryptography is restricted. Until 1999, France significantly restricted the use of cryptography domestically. In China, a license is required to use cryptography. Many countries have tight restrictions on the use of cryptography. In the United States, cryptography is legal for domestic use, but there has been much conflict over legal issues related to cryptography, export controls and civil liberties.