hashing and digital signatures

hash

represent data as a short string of text

a message digest, a fingerprint

is it possible to recover the original message from the digest

no its a one way trip

can hashes be used as a digital signature

yes for authentication, non repudiation and integrity

hash functions

take an input of any size

create a fixed size string

message digest, checksum

should you create hashes with the same input and if you do what happens

no creates collision

uses of hashing

verify a downloaed file and for password storage

password storage

stores a salted hash not the password and so we compare hashes during the authentication process instead

salt

random data added to a password when hashing

does every user get thier own random salt

yes

what doesnt work with salted hashes

rainbow tables

are hashes used with digital signatures

yes

how do digital signatures prove integrity

prove message wasn’t changed

how do digital signatures prove authentication

prove the source of the message

how do digital signatures prove non repudiation

makes sure the signature isn’t fake

process of creating a digital signature

verification of digital signatures