In cryptographic operations, encryption is the process of transforming information (referred to as plaintext/data) using an algorithm (called cipher) to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information (in cryptography, referred to as cipher text). In many contexts, the word encryption also implicitly refers to the reverse process, decryption (e.g. “software for encryption” can typically also perform decryption), to make the encrypted information readable again (i.e. to make it unencrypted).
Computer encryption uses the science of cryptography. As the human-based code is too easy for a computer to crack, most of the encryption systems belong to the one of two categories.
While in public-key (or asymmetric) encryption technique, uses one key (private key) to encrypt a message while another key (public key) to decrypt the message. Public-key encryption uses the combination of a private key and a public key. The private key is kept secret and is only known to the person who encrypts the message, while the public key is freely disseminated which helps to verify the message. To decode an encrypted message, receiver uses the public key of the sender and his own private key.
In symmetric-key encryption technique single key is used to encrypt and decrypt the message. When there is a need to encrypt large amounts of data symmetric-key encryption techniques are used.
Encryption and decryption processes are very important for all kind of digital signatures including PDF digital signatures.
