There are three basic encryption methods: hashing, symmetric cryptography,
and asymmetric cryptography. Each of these encryption methods have
their own uses, advantages, and disadvantages. All three of these
encryption methods use cryptography, or the science of scrambling data.
Cryptography is used to change readable text, called plaintext, into an unreadable secret format, called ciphertext,
using a process called encryption. Encrypting data provides additional
benefits besides protecting the confidentiality of data. Other
benefits include ensuring that messages have not been altered during
transit and verifying the identity of the message sender. All these
benefits can be realized by using basic encryption methods.
The first encryption method, called hashing, creates a unique fixed length signature of a group of data. Hashes are created with an algorithm,
or hash function, and are used to compare sets of data. Since a hash
is unique to a specific message, any changes to that message would
result in a different hash, thereby alerting a user to potential
tampering.
A key difference between a hash and the other two encryption methods is that once the data is encrypted,
the process cannot be reversed or deciphered. This means that even if a
potential attacker were able to obtain a hash, he would not be able to
use a decryption method to discover the contents of the original
message. Some common hashing algorithms are Message Digest 5 (MD5) and
Secure Hashing Algorithm (SHA).
Symmetric cryptography, which is also called private-key
cryptography, is the second encryption method. The term "private key"
comes from the fact that the key used to encrypt
and decrypt data must remain secure because anyone with access to it
can read the coded messages. This encryption method can be categorized
as either a stream cipher or a block cipher,
depending upon the amount of data being encrypted or decrypted at a
time. A stream cipher encrypts data one character at a time while a
block cipher processes fixed chunks of data. Common symmetric encryption
algorithms include Data Encryption Standard (DES), Advanced Encryption
Standard (AES), International Data Encryption Algorithm (IDEA), and Blowfish.
Asymmetric, or public key, cryptography is the last encryption
method. This type of cryptography uses two keys, a private key and a
public key, to perform encryption and decryption. The use of two keys
overcomes a major weakness in symmetric key cryptography in that a
single key does not need to be securely managed among multiple users.
In asymmetric cryptography, a public key is freely available to everyone
while the private key remains with receiver of ciphertext to decrypt
messages. Algorithms that use public key cryptography include RSA and
Diffie-Hellman.
