Symmetric Key Encryption

Symmetric Key Encryption

Hello dear friends! How are doing I hope all of you are fine. Today I have brough you another information system security post. So far we have discussed about many system security details. If you can remember we firstly had a brief intro to encryption. Then secondly we learned about different ciphers. As per that we discussed ciphers can be divided into types. They are block ciphers and stream ciphers or substitution ciphers or transpositions. We do the encryption based on any method above. Ciphers are the algorithm to do the encryption. Apart from those ciphers encryption also done as keys. When encryption is doing based on keys it can divide into two parts. They are public key encryption and private key encryption. So today we are going to learn about one of the types which is symmetric key encryption.

You already know the encryption method we are going to discuss today is based on keys. There are two keys available for the encryption. They are private key and the public key. Private key is shared only among the communicating two parties. Public key can be shared among any one. In private key encryption same key is using to do the both encryption and decryption. This method is also knowing as symmetric key encryption. Private key encryption is faster than the public key encryption.

Usage of Symmetric key encryption

  • Symmetric key is commonly use as session keys for confidential online communications.
    • EX-: Transport layer security and internet protocol security protocols use symmetric key encryption.
  • To do the bulk encryption of email messages and document files.
    • EX-: Secure/multipurpose internet mail extensions uses symmetric key for confidential mail, encrypting file system.

There are many symmetric key algorithms available now a days. Now let’s discuss how those encryption algorithms are working. Symmetric key algorithms are AES,DES and 3DES.

Symmetric Key Encryption – DES Algorithm

Now firstly let’s learn about DES algorithm. DES is a combination of two encryptions. In DES text is encrypting twice. Firstly it is encrypting the plain text message. Then it is again encrypting the encrypted message.

DES Algorithm Steps

  • In the first step the input is dividing into 64 bit blocks.
  • Then those 64 bits in the block get permutated.
  • Permutated 64 bits blocks then break into 32 bits blocks each.
  • 56 bits long key combined with right half and substitute and permutation happens.
  • The result will combine with the left half and create result
  • Initial right block becomes the new left.
  • Like this 16 cycles happens. A cycle begins after 32 bit block creation.

Symmetric Key Encryption – AES Algorithm

The AES algorithm was born on late 1999. It was made by two great cryptographers called Vincent Rijmen and Joan Deamen. AES algorithm also use uses a key to encryption. Unlike DES, AES uses several key lengths to encryption. So it can uses either 128 bits, 192 bits, 256 bits length keys for the encryption. As DES has 16 cycles based on the key length AES has 10,12,14 cycles respectively with the key size.

Differences & similarities of AES and DES algorithms

Introduced at year 1976Introduced at year 1999
64 bit length block size128 bit length block size
56 bits length key is used 128, 192, 256 bits length key is used
16 cycles10, 12, 14 cycles
Substitution, permutation is used for the encryption as mechanisms. Substitution, shift, bit mixing is used for the encryption as mechanisms.
Met confusion and diffusion Met confusion and diffusion
Closed Open
SecretSecret but public comments are acceptiing
Differences & similarities of AES and DES algorithms

Symmetric Key Encryption – 3DES Algorithm

3DES has little bit changes when comparing DES. In 3DES 3keys are using to do the encryption instead of using one. That’s why it is called as triple DES. C = E(K3, E(K2, E(K1,P)). In this method firstly the plain text will encrypted using a key and create the cipher text. After that encrypted text will encrypted again with another key. And again that happens. The encryption happens at three times.


I hope from this you get many details about symmetric key encryption or the private key encryption. From another post we will discuss about public key encryption and other things. Please like and share this article if you like this. Also don’t forget to comment. We will meet again with another interesting topic. Till then good bye!

Audy Ranathunga

Audy Ranathunga, Author of myexamnote is our most experienced author. She has been working as a blog post writer for 4 years. She joined with myexamnote before 1 year ago and she has contribute lots of valuable posts for readers.

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    Sanka Maduranga

    Thank you for sharing your knowledge with all of us.

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