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Security Fundamentals & Crypto · Foundational

Plaintext

Readable, unencrypted data that is input to an encryption algorithm or output from decryption.

Definition

Plaintext (sometimes called cleartext) is the original intelligible message. Strictly, cleartext refers to data never intended to be encrypted, while plaintext is the input to a cipher, though the terms are often used interchangeably. Protocols that send credentials in plaintext, such as Telnet and FTP, are considered insecure.

Example

A password sent over Telnet travels as plaintext that any packet sniffer can read.

Exam tip

Replace plaintext protocols (Telnet, FTP, HTTP) with encrypted alternatives (SSH, SFTP, HTTPS).

Related terms