1. Explain briefly how the following substitution ciphers can be broken: Caesar cipher, Simple substitution cipher, Vigenere cipher.
Answer
A caesar cipher can be broken by using frequency analysis. Frequency analysis is the assessment of the frequency that letters appear in ciphertext. To break a simple substitution cipher, a more complex frequency analysis is required because you need to assess the punctuation and numbers in the message. To break, a vigenere cipher, you need the keyword with which you can work backards.
2. Define symmetric encryption.
Answer
Symmetric encryption is an algorithm for cryptography that uses the same keys for both encryption of plaintext and decryption of ciphertext. The keys may be identical or there may be a simple transformation to go between the two keys