cryptographic hashes

Question 1

unkeyed hash function

Answer 1

function from all possible messages to finite set of possible message digests

Question 2

family of keyed hash function

Answer 2

four-tuple
X possible messages
Y finite set of possible authentication tags
for each k, there is a hash function

Question 3

message digest code

Answer 3

unkeyed hash function

Question 4

compression

Answer 4

maps x to y of fixed length

Question 5

computability

Answer 5

h(x) is easy to compute

Question 6

Message digest strengthening

Answer 6

addition of length-block x_(r+1) containing the binary representation of b