Substitution Techniques
The symmetric key cryptographic method employs one secret key for the operations of encryption and decryption. Substitution techniques provide two significant approaches, wherein elements (letters, characters) from the plaintext message are replaced with new elements according to the rules based on the secret key.
- Caesar Cipher: Caesar cipher has since their predictability is so complete and no complexity is invested.
- Monoalphabetic Ciphers: This is where the ciphers use one rule of substitution throughout the message. This may involve replacing letters with numbers, symbols, or another set of letters in another order.
- Playfair Cipher: Implementation of repeated letters or letter pairs can expose patterns, and cryptanalysis techniques exist to exploit them.
- Hill Cipher: This cipher operates on blocks of letters (typically bigrams or trigrams) using a matrix multiplication approach. The Hill ciphers have a limitation on key size and susceptibility towards cryptanalysis for larger key sizes.
- Polyalphabetic Ciphers: This is the type of cipher where any one of the letters in the plaintext is substituted by a different letter to keep frequency analysis challenging. For example, the Vigenère cipher operates with a keyword that would determine the shift value for each letter in the plaintext.
- One-Time Pad (OTP): It is a theoretically impossible cipher where the key is a random string of characters that is exactly as long as the message itself. The key is used for a single encryption and then discarded.
Symmetric Key Cryptography
Symmetrical Key Cryptography also known as conventional or single-key encryption was the primary method of encryption before the introduction of public key cryptography in the 1970s. In symmetric-key algorithms, the same keys are used for data encryption and decryption. This type of cryptography plays a crucial role in securing data because the same key is used for both encryption and decryption.
In this article, we will cover the techniques used in symmetric key cryptography, its applications, principles on which it works, its types and limitations as well as what type of attacks in the digital world it gets to face.