Public & Private Key Encryption Explained
Encryption is a concept that has become commonplace with the proliferation of home wireless networks, where one wants to keep information from being understood by everyone. Actually, encryption has been around for centuries. One of the earliest examples is the Caesar Cipher, named after Julius Caesar. This substitution encryption process had an individual take the alphabet and shift the characters over a certain number based off of an algorithm. Thus, if the result was five characters to the right, an "a" would be treated as "f", "c" a "h", etc. While this algorithm may not be currently used, public and private key encryption are two methods commonly used now.
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Basics of Encryption
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Encryption takes a series of algorithms, or mathematical statements, to scramble data from its original format into one undecipherable. The initial information is called plaintext, which has encryption applied to it and results in ciphertext. Ciphertext cannot be understood under normal conditions without the reverse, or decryption, applied to the ciphertext. When reversed, one is left with plaintext.
What is a Key?
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In cryptography, a key is the information needed to take data from one format to another. In the case of the Caesar Cipher, the key would be the knowledge that you have to shift five characters right in the alphabet to decode a message. With modern encryption schemes, a file contains information needed to encrypt or decrypt information.
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Private Key Encryption
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Private key encryption, or symmetric encryption, is where one key will encrypt and decrypt information. The benefit of this approach is that the process is very fast as a single key is used for both ends of the encryption chain. The concern is protecting the key from others as a single point of potential security failure. Key management is a primary concern when using private key encryption.
Public Key Encryption
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Public key encryption, or asymmetric encryption, is a solution to the perceived problem of key management found in private key encryption. There is a pair of keys used, a public and private key. The public key is widely distributed to anyone who wants to privately communicate with the other party. That party has the private key, which is paired to the public key. While the public key is widely available, the private key is never shared.
Although public key encryption deals with the key management issue found in private key encryption, it is typically slower than private key encryption. This is due to the fact that there is additional overhead with multiple keys that need to be managed.
Examples of Private and Public Encryption
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DES, or Data Encryption Standard, is an example of a modern-day encryption scheme. In most applications, especially transacting business via the web, public key encryption is commonplace. When you go to Amazon.com to make a purchase, you are using what is called SSL, or Secure Sockets Layer, to encryption the session between yourself and Amazon. This process uses public key encryption.
In adddition, there are hybrid approaches to encryption. A popular example of this is the use of PGP, or Pretty Good Privacy, which uses a combination of private key and public key encryption.
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