Encryption: Symmetric and Asymmetric algorithms

In present days, individuals and incorporation are creating massive amount of digital data in every fraction of time. As the quantity of this data is increased threats to unauthorized access to its  has also been rose up. To cope up with the unauthorized access to data one of the best technique used in present time is encryption. 

What is encryption ?

Encryption is a technique used to convert the contents of plain data/information to be saved or transferred to a cipher text with the help of an algorithm in association to an encryption key. This encryption key is shared with the people who require access to the data. The person who have that key can convert that cipher text back to original text using that key with the help of the reverse algorithm. Converting the cipher text back to original text is called decryption.

How encryption is different from password security?

Using a key to access the data secured by encryption technique seems similar to securing the data with the password but under the skin both vary a lot in their purpose and technique. The password security is usually the first line of defense to protect the data from unauthorized access. But the password security can never be considered full proof. In that case encryption is fallback technique and can also be the only line of defense in absence of any password security.if somebody get access to the stored data by somehow bypassing the password security or eavesdrop the unsecured data being communicated through a channel. In that case even if someone gets the access to the data and if it is encrypted it would make no sense to that person unless he gets the key to decrypt it. 

Manipulation Techniques used in Encryption

All conventional encryption algorithms are based on two kinds of manipulation of the data: Substitution and Permutation.

Substitution: Each element of the plaintext is mapped into another element using in association with a key. For example, the letters in word apple are mapped to its 3rd next letter ending up with the cipher word crrng. So the key here can be considered as 2. The encrypt function of algorithm should add 2 to each letter of plain text to produce a cipher key. While the decryption function should reduce 2 from each letter in cipher text in order to reverse it obtain to plain text.

Permutation: The elements in the plaintext are rearranged. Permutation is also called transposition. For example, every pair of letters in word apple are swapped withto its 3rd next letter ending up with the cipher word palpe. So the key here is swapping each pair of letters in the world. So the key here can be considered as 2. The encrypt function of algorithm should swapping each pair of letters in plain text to produce a cipher key. While the decryption function should do the reverse in cipher text in order to reverse it to obtain plain text from it.

The examples given here are just the basic one. In actual encryption algorithms keys can involve a number, a word, or just a string of random letters which are 64 bit,128 bit, 256 bit long or now even 512 bit and 1024 bit which makes it almost impossible to guess.

Symmetric and Asymmetric Algorithms

Apart from the manipulation technique the encryption techniques are best classified on the basis of key(s) used for encryption and decryption of data.

Symmetric and Asymmetric

Symmetric Encryption

Symmetric Key Encryption algorithms use the same key to encrypt and decrypt the information. The person who wants to send the information or store the information in a secret way encrypts it using a secret key which he shares with only to receiver or to whom he want to provide access to that information in case of stored information.

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The advantage of this technique is that generating the keys for encrypting the information is fairly simple and the algorithms are very inexpensive and easily available.

The drawback of this technique is that the if some unauthorized person gets access to shares symmetric key he can decrypt the information and get access to that. Because of this drawback these algorithms are not much suitable for transferring data on a network unless the symmetric key is also secured with some other technique. However it is sufficient to use these algorithm to store the information securely in encrypted form for personal use only when there is no need to share the key with other people.

The common algorithms which use the symmetric encryption key technique are AES, DES and Blowfish etc.

Asymmetric Encryption

Asymmetric Encryption technique algorithms also called Public Key Encryption algorithms use separate keys for encryption and decryption. The receiver who wants to receive information generate two keys using asymmetric algorithms: Public Key and Private Key. The Public key is shared with the senders from whom the receive wants to receieve the information. The senders encrypts the information with the public key and sends it to receiver. The receiver uses its private key to decrypt the information.

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The advantage of this encryption technique is that only the receiver know the private key to decrypt the information. The Public key can only be used to encrypt the information but can not be used to decrypt it. So the people who have the Public key to encrypt and send the information cannot decrypt the information sent by other. Only receiver can decrypt it with its private key.

The Asymmetric Encryption algorithms are widely used to send the data over HHTPS and FTPS secure protocol using the Digital Certificates and Public Key Infrastructure.

The most commonly used Assyetric encryption techniques are RSA, DSS and ECDSA.

If you are curious about how two different number can be encrypt and decrypt the same information.You can read an article on how to generate the keys here.

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