IDEA (International Data Encryption Algorithm) is an encryption algorithm developed at ETH in Zurich, Switzerland. It uses a block cipher with a 128-bit key, and is generally considered to be very secure. It is considered among the best publicly known algorithms. In the several years that it has been in use, no practical attacks on it have been published despite of a number of attempts to find some. IDEA is patented in the United States and in most of the European countries. The patent is held by Ascom-Tech. Non-commercial use of IDEA is free. Commercial licenses can be obtained by contacting Ascom-Tech.