Terminology

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A message sent unencrypted is said to be in cleartext or plaintext. A message sent encrypted is said to be in ciphertext.

The US government used to restrict the strength of encryption it allowed to be included in software for export - beyond a certain strength, encryption is regarded as of military value. In January 2000 these restrictions were mostly removed. Nevertheless a lot of encryption software still exists that was designed in that period to be exportable. The term "export cipher" means an algorithm and key length designed to be exportable under these regulations.

The information given here is believed to be correct at the time of writing, but remember that typical computer power and legal requirements are constantly changing.

The word "cipher" is often used to mean an encryption algorithm. A particular algorithm with a particular key length is often referred to by the algorithm's abbreviated name followed by a hyphen and the key length. For example, RC4-40 means "Rivest Cipher 4 with 40-bit keys".

Short keys are usually called small or weak keys.