UNIX Password System Uses DES encryption as if it were a hash function 一 Encrypt NULL string using password as the key Truncates passwords to 8 characters! low-order 7 bits of each character is used to form the 56-bit DES key -Artificial slowdown:run DES 25 times Problem:passwords are not truly random -With 52 upper-and lower-case letters,10 digits and 32 punctuation symbols,there are 948~6 quadrillion possible 8-character passwords -Humans like to use dictionary words,human and pet names 1 million common passwords 44 UNIX Password System  Uses DES encryption as if it were a hash function ─ Encrypt NULL string using password as the key ● Truncates passwords to 8 characters! ● low-order 7 bits of each character is used to form the 56-bit DES key ─ Artificial slowdown: run DES 25 times  Problem: passwords are not truly random ─ With 52 upper- and lower-case letters, 10 digits and 32 punctuation symbols, there are 948 ≈ 6 quadrillion possible 8-character passwords ─ Humans like to use dictionary words, human and pet names ≈ 1 million common passwords