Cryptography is the science of encoding and decoding data securely.
Encryption is a process by which data readable to anybody (known as plaintext) is converted by a mathematical process into a form that can only be decoded and understood by the holders of a particular key (known as ciphertext). This key usually takes the form of a large numerical value, although it may be represented by a word or phrase for ease of memory and transmission.
Two broad types of encryption are:
- Symmetric-key cryptography
- Public-key cryptography
With the symmetric-key version, the same key or password is used to encrypt and decrypt the data. With a public-key or asymmetric cipher, one key is used for encryption and another for decryption. The encryption key is often publically available, while the decryption is held private by the recipient.
Decryption reverses this process so that formerly encrypted data may be accessed as plain data.