The exact substitutions and transformations performed by the algorithm depend on the

Symmetric EncryptionSymmetric encryption, also referred to as conventional encryption or single-keyencryption, was the only type of encryption in use prior to the introduction of public-key encryption in the late 1970s. Countless individuals and groups, from JuliusCaesar to the German U-boat force to present-day diplomatic, military, andcommercialusers, have used symmetric encryption for secret communication. It remainsby far the more widely used of the two types of encryption.A symmetric encryption scheme has five ingredients (Figure 21.1):• Plaintext:This is the original message or data that is fed into the algorithm asinput.• Encryption algorithm:The encryption algorithm performs various substitutionsand transformations on the plaintext.• Secret key:The secret key is also input to the encryption algorithm. The exactsubstitutions and transformations performed by the algorithm depend on the key.• Ciphertext:This is the scrambled message produced as output. It depends onthe plaintext and the secret key. For a given message, two different keys willproduce two different ciphertexts.• Decryption algorithm:This is essentially the encryption algorithm run in reverse.It takes the ciphertext and the secret key and produces the original plaintext.There are two requirements for secure use of symmetric encryption:1. We need a strong encryption algorithm. At a minimum, we would like thealgorithm to be such that an opponent who knows the algorithm and hasaccess to one or more ciphertexts would be unable to decipher the ciphertextor figure out the key.This requirement is usually stated in a stronger form:Theopponent should be unable to decrypt ciphertext or discover the key even if heor she is in possession of a number of ciphertexts together with the plaintextthat produced each ciphertext.2. Sender and receiver must have obtained copies of the secret key in a securefashion and must keep the key secure. If someone can discover the key andknows the algorithm, all communication using this key is readable.

Exploring the world of Network Security!

Symmetric encryption , also referred to as conventional encryption , secret - key , or single key encryption , was the only type of encryption in use before the development of public - key encryption in the late 1970s . It remains the most widely used of the two types of encryption . A symmetric encryption scheme has five ingredients as shown in below diagram.

It's a simplified Model of Conventional Encryption.

1. Plaintext : This is the original message or data that is fed into the algorithm as input.

2. Encryption algorithm : The encryption algorithm performs various substitutions and transformations on the plaintext.

3. Secret key : The secret key is also input to the algorithm . The exact substitutions and transformations performed by the algorithm depend on the key.

4. Ciphertext : This is the scrambled message produced as output. It depends on the plaintext and the secret key . For a given message , two different keys will produce two different ciphertexts.

5. Decryption algorithm : This is essentially the encryption algorithm run in reverse . It takes the ciphertext and the same secret key and produces the original plaintext.

There are two requirements for secure use of symmetric encryption :

1. First we need a strong encryption algorithm . At a minimum , we would like the Algorithm to be such that an opponent who knows the algorithm and has access to one or more ciphertexts would be unable to decode the ciphertext or figure out the key . This requirement is usually stated in a stronger form : The opponent should be unable to decrypt ciphertext or discover the key even if he or she is in possession of a number of ciphertexts together with the plaintext that produced each ciphertext.

2. Second sender and receiver must have obtained copies of the secret key in a secure fashion and must keep the key secure . If someone can discover the key and knows the algorithm , all communication using this key is readable .

It is important to note that the security of symmetric enryption depends on the secrecy of the key , not the secrecy of the algorithm. That is , it is assumed that it is impractical to decrypt a message on the basis of the ciphertext plus knowledge of the encryption / decryption algorithm . In other words , we do not need to keep the algorithm secret ; we need to keep only the key secret.

Some examples of where symmetric cryptography is used are: Payment applications, such as card transactions where PII needs to be protected to prevent identity theft or fraudulent charges. Validations to confirm that the sender of a message is who he claims to be. Random number generation or hashing.

I will come up with more related topics such as public key and digital signatures in my next article!

Till then, Ghani Khamma.

What ingredient of symmetric encryption performs the various substitutions and transformations on the plaintext?

What ingredient of symmetric encryption serves as the scrambled message produced as output that depends on the plaintext and the secret key?

What are the two approaches used to attacking a cipher?

What are the basic functions used in classical encryption techniques?