A substitution cipher replaces each letter of the plaintext with a letter found by moving [latex]n[/latex] places down or up the alphabet. Example: Using a shift of 3, “ABC” becomes “DEF.”
A transposition cipher rearranges the letters of the plaintext. Example: “HELLO” can become “HLELO.”
“THISISATEST”
“HELLO WORLD”
Key distribution problems, Susceptibility to brute-force attacks.
Faster encryption/decryption, Simpler algorithms.
Key pairs consist of a public key (for encryption) and a private key (for decryption). The public key is shared openly, while the private key remains secret.
To verify the authenticity of a message or document.