Plaintext
In cryptography, plaintext is information a sender wishes to transmit to a receiver. Cleartext is often used as a synonym.
Plaintext has reference to the operation of cryptographic algorithms, usually encryption algorithms, and is the input upon which they operate. Cleartext, by contrast, refers to data that is transmitted or stored unencrypted (that is, 'in the clear').
Overview
Before the computer era, plaintext most commonly meant message text in the language of the communicating parties.
Since computers became commonly available, the definition has expanded to include:
messages (for example, email messages)
document content such as word processor and spreadsheet files
audio and video files, digital photographs and any other multimedia
files containing other files such as Zip files or ISO images
ATM, credit card and other banking information
sensor data
any other data that a person wishes to keep private
Much of this data is not directly meaningful to humans, being already transformed into computer manipulable forms.
While the original definition implied that the message could be read by a human being, the modern definition emphasizes that a person using a computer could easily interpret the data.
