Encryption is the process of converting data from its normal, readable state, called plaintext, in protected, secure data called ciphertext so that it can only be read by the intended recipient or recipients, who are able to decrypt it using a secret key. Encryption is a practice dating back to ancient warfare, when it was important to send messages that one’s enemies could not access. There are many types of encryption that can be categorized in several ways: the material of the encrypt, the means of encryption, the methodology of encryption employed including the particular algorithm used, and/or earlier or more recently invented/used encryption systems.
There are different kinds of encryption that work all the time on one particular type of material and other types of encryption that the user controls and applies on an as-needed basis. Email encryption applies to all outgoing email from a system. Hard disk encryption — also known as full-disk encryption or FDE, whole disk encryption, hard drive encryption, or disk encryption — encrypts all files of every kind that are found on a computer hard drive. Pages with the HTTPS protocol encrypt all transactions carried out through them, allowing credit card payments over the Internet. In contrast, a user can choose to secure a particular pdf, for example, and — depending on the software program used — require a password to open it and/or to change it or prevent any editing or limit or prohibit printing.
Types of encryption can also be distinguished by being software-generated encryption or hardware-based encryption. For example, hard disk encryption has primarily been carried out by software. However, the group of hard drive manufacturers making up the Trusted Computing Group (TCG) agreed in 2009 to an encryption standard for hard disks, which they named the TCG Storage Specification. When fully enacted, hard disks will automatically encrypt, rather than needing a separate, added software program to accomplish this.
Another way to distinguish kinds of encryption is by how they work. Encryption methodology may be symmetric, meaning they have a single key that is used for both encryption and decryption and which must be sent along with a message to ensure that it can be decrypted by the recipient. On the other hand, it can by asymmetrical, in which case, the sender uses the recipient’s public key to encrypt the plaintext, and the recipient’s computer uses the recipient’s private key to decrypt it. The use of different algorithms, different key lengths, and block cipher or streaming cipher are other distinguishing factors. One could also distinguish types of encryption that are considered outdates — like DES (Data Encryption Standard) and WEP (Wired Equivalent Privacy), from newer, better encryption — like Triple DES and WAP2 (WiFi Protected Access, version 2), which uses AES (Advanced Encryption Standard).