Explain the meaning of Symmetric encryption.

Symmetric encryption is the process of encoding and decoding messages using the same key. An important aspect of this type encryption is to ensure that the key is not compromised and that only the sender and receiver have access to the key used to modify the plain text.
Substitution is one technique used in symmetric encryption. The first part of this activity is intended to illustrate symmetric encryption using substitution. The second part of this activity illustrates the block cipher technique using a product technique that emulates the Feistel structure with substitution and transposition.