Encryption algorithms

Earlier I was talking about SMS Banking and One Time Passwords. So I guess it is the best time for me to refer to encryption algorithms as well. This might not be a familiar topic to a person who is not involved with technology much. Therefore I would try to write as simply as possible.


Simply said, encryption is used to convert data (including passwords) into a format which would make it harder or almost impossible for intruders to view. It is especially important when data is being sent over insecure platforms (E.g.:- Internet, outside networks other than your own). There are several encryption methodologies. Some are specifically used as password encryption algorithms.


The purpose of using encryption algorithms are, 

• Authentication - means, proving one's identity before granting access.
• Privacy and confidentiality - ensuring that outsiders cannot read data intended for specific parties.
• Integrity - ensuring that the message has not be modified in any way before it arrives to the intended recipient.
• Non-repudiation - ensuring that a message is truly originated from the sender.

The most popular encryption algorithms can be listed and described as follows.

Symmetric Algorithms

This uses a single key to encrypt and decrypt data. These encryption algorithms are usually fast. So they are well suited for encrypting blocks of messages at once. 

E.g.:- 

• DEA (Data Encryption Algorithm) - specified within the DES (Data Encryption Standard)
• 3DES (Triple DES) - a more reliable version
• AES (Advanced Encryption Standard) - has even become a government standard in USA
• FEAL - developed in Japan
• SKIPJACK - a top secret algorithm developed in USA for highly secured data

Asymmetric Algorithms

Asymmetric algorithms involve a pair of relative keys that encode and decode messages. 

One key is used to encrypt data into ciphertext and the other key decrypts it back into plaintext.  The encryption method involves multiplying two large prime numbers to generate a larger number that is almost impossible to revert to the original form. Asymmetric algorithms are also called as Public-key cryptography.

However, asymmetric algorithms tend to be slower than the symmetric method. Therefore, they aren't recommended for encrypting large amounts of data like the symmetric encryption method. 

So what is the advantage of such a scheme than the symmetric method?

It actually happens to be the utilization of two keys. Of the two keys, one key is used as a public key and this public key can be made publicly available, according to its name. This enables anyone to encrypt private messages. Yet, the message can only be decrypted by the party that owns the relative private key. So the real advantage of such an encryption algorithm happens to be in proving the actual origin to ensure to overall integrity of communications.

Hash Algorithms

What happens here is that it converts data of arbitrary length into a smaller fixed length(alos known as message digest/fingerprint). Such algorithms are one-way functions. Hash algorithms are often generated by the DES algorithm to encrypt online banking transactions and other communications where messages can't afford to be corrupted and more commonly used in password encryptions.

E.g.:-

• MD5 - a 128 bit message digest function
• SHA - considered more secure than MD5 since  it produces a digest of 160 bits