In cryptography, encryption is the process of encoding a message or information in such a way that only authorized parties can access it and those who are not authorized cannot.
Encryption does not itself prevent interference, but denies the intelligible content to a would-be interceptor.
Unencrypted data, often referred to as plaintext, is encrypted using an encryption algorithm and an encryption key. This process generates ciphertext that can only be viewed in its original form if decrypted with the correct key. Decryption is simply the inverse of encryption, following the same steps but reversing the order in which the keys are applied.
Today's most widely used encryption algorithms fall into two categories: symmetric and asymmetric.
Fig: - Encryption operation.
Encryption was almost exclusively used only by governments and large enterprises until the late 1970s when the Diffie-Hellman key exchange and RSA algorithms were first published -- and the first personal computers were introduced. By the mid-1990s, both public key and private key encryption were being routinely deployed in web browsers and servers to protect sensitive data.
Encryption is now an important part of many products and services, used in the commercial and consumer realms to protect data both while it is in transit and while it is stored, such as on a hard drive, or flash drive (data at rest).