Encryption software turns readable text into unreadable cipher by applying algorithms that can only be reversed by the passphrase or key. There are secure forms of encryption and insecure forms, as weak algorithms can be broken by the same computer power that generates strong algorithms. The current standard adopted by the US Government is the Advanced Encryption Standard (AES), based on 128-bit blocks. The former standard known as the Data Encryption Standard (DES) is based on 56-bit blocks and is now considered insecure.
The AES standard was pulled from a larger pool of algorithms that were developed by Joan Daemen and Vincent Rijmen of Begium. Their encryption software is known as Rijndael. Two examples of competing encryption software in this category include Twofish and Serpent.
Encryption software like AES, Twofish and Serpent rely on a single shared password or key to encrypt and decrypt data, and for this reason they are known as symmetric schemes. This type of encryption software is used to secure stored data. It can also be used to encrypt an entire volume or hard drive. To use the drive, one must mount the volume using a passphrase. When one dismounts the drive, the volume returns to its encrypted state.
Asymmetric encryption schemes use a key pair to encrypt and decrypt data. This type of encryption is often used in email and other forms of communication. The key pair includes a private key and a public key that are linked or associated. The public key can be freely given to anyone to be used to encrypt data sent to the owner of the public key. Once something has been encrypted using the public key, only the private key of that key pair, held in confidence by the owner, can decrypt the data. Asymmetric encryption software is considered more secure than symmetric schemes because the decryption key is not shared.
In secure email conversations, both parties use encryption software to generate their own key pairs, then exchange public keys. Now each person can send encrypted mail to the other, and upon arrival, that person uses his or her private key to decrypt the mail. These operations can be done seamlessly by email plug-ins used with encryption software. Pretty Good Privacy® (PGP) is encryption software that works with some popular email programs, and the open-source version of PGP known as GnuPG can also be used with the Enigma™ plug-in in Mozilla® Thunderbird® for automatic encryption and decryption.
There are a plethora of encryption programs available online, many free. If you are looking for something to secure your stored data or for volume encryption, AES-type programs work well. If looking to encrypt your email, asymmetric programs based on key pairs provide the best security. In the latter case, differing programs might work with one another in certain cases, but it’s probably easier for people new to encryption to use the same encryption software to ensure compatibility.