Whole disk encryption, as the name implies, refers to the encryption of an entire physical or logical disk. While this is currently done mostly with software, hardware based disk encryption is a growing technology which is expected to surpass software products for whole disk encryption over the next few years. This form of encryption generally encrypts the entire contents of a disk or volume and decrypts/encrypts it during use after a key has been given. This means the data is protected from situations like laptop/disk loss or theft where the data would be encrypted and require a key to decrypt. It would not protect from situations like sending information over the network (e-mail, websites, etc) or from situations where the decryption key was already entered such as the user walking away from their logged-in computer.
When an individual wishes to encrypt a single file or group of files there are several options. Most encryption software has the ability to encrypt files individually using a password or other key. Many encryption programs have the ability to create an encrypted "virtual drive". This is an encrypted file that, when opened with the key, looks like another drive attached to the computer allowing the user to easily open and save files into an encrypted area. Some other applications, like MS Office and OpenOffice, have built-in, single-file encryption features.
This approach can protect against data disclosure on a lost or stolen computer, but only if all of the private information was encrypted. Individual file/folder encryption relies on user education and good practices to ensure that all appropriate information is encrypted.
Depending on how the encryption software is used, this approach can provide protection from data disclosure when transferring information over the network. E.g. an individual file can be encrypted and then sent as an email attachment, assuming the recipient has the ability to decrypt it.
Allowing multiple users to simultaneously access encrypted information is more complicated than a single user. The encryption software must allow the use of either multiple keys (i.e. one for each user) or a shared key (e.g. a shared password). Additionally, the software must deal with multi-user file locking issues (this is usually a problem with the virtual drive approach mentioned in the last section).
This approach can provide an additional layer of protection against the disclosure of highly confidential data on file servers in the event they are compromised. I can also help protect against disclosure on backup media as the files would remain encrypted when backed up.
This approach can get complicated if not all users have the encryption software installed, or they are not configured consistently. This could lead users being unable to access encrypted information or incorrectly believing they have encrypted information when they have not. For these reasons, special attention should be paid to how encryption software behaves and users should be educated to recognize the encryption status of files.
Encrypting information in a database can be done at a couple of levels. The application accessing the database can encrypt information before putting it into the database. This requires intelligence at the application level, but no additional database features. Many databases have built-in encryption functions which applications can use to encrypt data as it is written. This usually requires features at both the application and database level. An encryption application can sit between the application and database, encrypting/decrypting information as it is written and read. This requires buying and installing additional software, but may not require modifications to the application or database.
As mentioned earlier, some applications that aren’t specifically designed for encryption do have basic encryption functions. Most notably, common productivity suites like Microsoft Office and OpenOffice contain file encryption features. Be cautious of the quality of the built-in encryption features, even within the Microsoft Office product line, some versions (like Office 2007) have a good mechanism, others have poor ones (like Office 2000 and earlier) and still others require proper configuration to provide good protection (like Office 2003). These features can be very handy because they don’t require additional licenses, require less training and can be effective for both in transit and at rest encryption. Additionally, they can work well for file exchange since the recipient is more likely to have the ability to decrypt the file. In short, built-in encryption functions can be convenient options, but you should research their effectiveness before using them.
There are a couple of different levels to encryption with email, first is encrypting just an attached file and second is encrypting an entire message. Encrypting an attached file can be accomplished using any single-file encryption process that "sticks" to the file. Naturally, the recipient must have a way of decrypting the file. There are only a couple of commonly used email message encryption technologies, most notably S/MIME and PGP. While S/MIME support is integrated into many email clients, it requires users to have trusted certificates which can be complicated to properly deploy. Using PGP to encrypt email requires installing software, but there are both free and commercial options.
Both of these technologies also allow for digital "signing" of email without encrypting it. This signing process allows the recipient to be certain a message was not altered in transit, but does not protect the content from prying eyes.
Encrypting information while in transit on a network is one of the most common, and important, uses of encryption. One of the most popular forms of this encryption is Secure Sockets Layer (SSL)/Transport Layer Security (TLS), commonly used to encrypt web traffic in transit. Any web application that transmits or collects sensitive information should encrypt the information using SSL/TLS. There are a number of other uses for SSL/TLS encryption, including securing authentication for email communication between clients and servers. SSL/TLS can also be used for "tunneling" to encrypt other forms of network transmission that don’t have their own encryption features.
Another common network encryption technology is Secure Shell (SSH) which is largely used for encrypted terminal connections (replacing telnet) and encrypted file transfers (SFTP replacing FTP). Like SSL/TLS, SSH can also be used for tunneling.
A more general form of network traffic encryption is IP Security (IPSec), which operates at a more basic layer than SSL or SSH and can be applied to any network traffic. However, using IPSec requires common configuration between the two computers communicating, so it is generally used within a company/department rather than across the internet.
For wireless networks there are other encryption options that only encrypt information between the computer and the wireless access point. For this reason, they only protect from snooping on wireless and not after the information leaves the access point onto a wired network. The two most common forms are called Wired Equivalent Privacy (WEP) and WiFI Protected Access (WPA). WEP is no longer considered a secure protocol. WPA is much stronger, but has shortcomings and an updated WPA2 standard has been released which improves its security.