40-bit encryption
40 bit encryption is symmetric encryption using a key of 40 bits (5 bytes). This leads to a total of 440 possible keys, which sounds like a large number (it is over a hundred times the world's human population). However, it is possible to break this degree of encryption quite rapidly, in fifteen minutes with dedicated, albeit inexpensive, hardware, or a few weeks on a single mid-range home computer.
40 bit encryption is common in some very old software, when programs implementing significantly stronger algorithms could not be exported from the United States legally; however, it is now considered completely outdated, and some web servers will not communicate with a client which does not implement 128 bit encryption.