khoor zruog fubswrjudskb
E=13% T=9.1% A=8.2% O=7.5% I=7% N=6.7% S=6.3% H=6.1% R=6% D=4.3% L=4% C=2.8% U=2.8%
Caesar shifts each letter by a fixed amount. Vigenere uses a keyword for polyalphabetic substitution. RSA uses the difficulty of factoring large numbers for secure public-key encryption. Hash functions produce fixed-size digests where tiny input changes cause completely different outputs (avalanche effect).