What is a plaintext? What is a ciphertext?

When discussing encryption we frequently use two terms: plaintext andciphertext. The plaintext is the original message that the sender wants to securely deliver to the receiver. The ciphertext is the message that is actually transmitted over the insecure channel. Before transmission, the sender transforms the plaintext into the ciphertext-​this is encryption. When the ciphertext is received, the receiver must transform the ciphertext back into the plaintext-​this is decryption. To be secure, encryption and decryption must require that the sender and receiver possess some secret information or key. The goal of most encryption systems is to ensure that the ciphertext cannot be decrypted-​transformed back into the plaintext-​without that secret key. This prevents an adversary or anyone able to eavesdrop on the connection from recovering the original message plaintext.
Credits: Talking: Geoffrey Challen (Assistant Professor, Computer Science and Engineering, University at Buffalo). Producing: Greg Bunyea (Undergraduate, Computer Science and Engineering, University at Buffalo).
Part of the www.internet-c... online internet course. A blue Systems Research Group (blue.cse.buffa...) production.