In data communications, cleartext is the form of a message or data which is transferred or stored without cryptographic protection. It is related to, but not entirely equivalent to, the term "plaintext". The phrases, "in clear" and "in the clear" are equivalent. For example, "The keys in the Foo protocol are exchanged as cleartext." would mean that the keys are not encrypted during transmission.
Cleartext material is sometimes in plain text form, meaning a sequence of characters without formatting, but this is not strictly required as the sense is 'no protection from snooping', not 'no special software required to read'. Thus, "The form letter we wrote is stored on your disk in cleartext, that is -- in Microsoft Word format without encryption. And so is the email I sent -- that's in plain text (i.e., ASCII) form".
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