What Is File Encryption?
Encryption is the process of securing the contents of a file or message by encoding it. An encrypted message looks like gibberish, unless you can decode it using a key to translate those random characters back into real text or data. The Internet has made it simple to share data with others, creating a growing personal need for privacy. Not all encryption schemes are the same, however, nor are they foolproof.
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Private Key
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Private key encryption uses one key to both encrypt and decrypt the data. Advantages of private key encryption algorithms are that they process the data quickly and can be simply encoded into hardware.
But private key schemes have a major failing: Anyone who has the key can encrypt or decrypt the data. Conversely, if you don't have the key, you can't. This means you have to find a means to securely distribute the key to others. As more people have the key, the information becomes less secure.
Public Key
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In 1975 Whitfield Diffie and Martin Hellman invented a solution to the problems inherent in private key cryptography. Their technique, called public key encryption, involves the use of two separate keys that are mathematically related. The public key is used to encrypt data. It can be safely distributed to many people. The matching private key is the only means to decrypt data encrypted with that public key. This combination of keys is referred to as a "key pair."
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Authentication
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Public key encryption can function as a form of authentication. PGP, short for "pretty good privacy," is a widely available encryption program. According to the PGP user's guide, encrypting a message also digitally signs it. A message that can be decrypted using a user's public key must therefore have been previous encrypted by the matching private key. Furthermore, successful decryption indicates that the message was not previously altered by a third party.
Email
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Email is an inherently insecure medium. System administrators can read "spool files" containing en-route emails. Postmasters receive bounced mails in their entirety. Law enforcement agencies can request this content at will. The Electronic Communications Privacy Act grants administrators legal justification to read your mail under three conditions: suspicion of intent to cause harm to the system or another user, monitoring consent by either the sending or receiving party and inspection by the system owner of employee communications. Encryption is the only way to secure privacy for your email communications.
Considerations
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Public key encryption is not a perfect solution. It's much slower than private key encryption, running from 100 to 1,000 times slower than equivalent private key systems because of processing overhead. Use of encryption in international communications is legally problematic. The U.S. government regulates encryption, classifying it as a munition under the ITAR (the Internation Traffic in Arms Regulations). Encrypted data can be exported but only using encryption keys of up to 40 bits in length. Key length is a measure of encryption complexity. Longer keys are more complex. A 40-bit key is not complex enough to prevent the encryption scheme from being breakable.
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References
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- Photo Credit Image by Flickr.com, courtesy of Kevin Dooley
