Question 1

How can you identify which cipher was used to encrypt a message?

Accepted Answer

Cipher identification involves analyzing the ciphertext for patterns. Classical ciphers like Caesar show frequency distributions similar to the original language. Vigenere produces repeating patterns detectable with Kasiski examination. Modern symmetric ciphers like AES produce output indistinguishable from random data. Block ciphers produce fixed-length blocks, while stream ciphers match input length. The format, character set, and context all provide clues.

Question 2

What is the difference between classical and modern ciphers?

Accepted Answer

Classical ciphers (Caesar, Vigenere, Playfair) operate on individual letters or small groups and are vulnerable to frequency analysis. Modern ciphers use complex mathematical operations on binary data — symmetric ciphers like AES use the same key for encryption and decryption, while asymmetric ciphers like RSA use a key pair. Modern ciphers are computationally secure when properly implemented.

Cipher Identifier

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