CAST-128 (also known as CAST-5) is a symmetric key encryption algorithm that was developed by the Canadian Institute for Telecommunications Research (CITR) in 1996. It was designed to be a fast and secure encryption algorithm that could be used in a variety of applications.

Here’s a simple explanation of how CAST-128 works:

  1. The sender uses the CAST-128 encryption algorithm and a secret key to encrypt the data. The encrypted data is called a “ciphertext.”
  2. The sender transmits the ciphertext to the recipient over a network, such as the internet.
  3. The recipient uses the CAST-128 decryption algorithm and the same secret key to decrypt the ciphertext and recover the original data.


Some examples of applications that may use CAST-128 include:

  • Network devices: CAST-128 is often used to encrypt data transmitted over networks, such as in VPN connections or secure wireless networks. Many network devices, such as routers and switches, support CAST-128 as an encryption option.
  • Encryption software: CAST-128 is supported by many encryption software programs, such as PGP (Pretty Good Privacy) and GnuPG (GNU Privacy Guard), which can be used to encrypt files and messages.
  • File archivers: Some file archiving programs, such as 7-Zip and WinRAR, support CAST-128 as an encryption option for protecting the contents of archived files.

CAST-128 uses a key length of 128 bits, which makes it resistant to attacks. It is known for its fast performance and is considered to be a strong encryption algorithm. CAST-128 is used in a variety of applications, including encrypting data transmitted over networks and protecting data stored on devices such as laptops and smartphones.

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