Digital Signatures

Question 1

What 2 problems does Public Key Encryption solve?

Answer 1

Key Management issue.
Authentication (Proving origin of data).

Question 2

What is the formula to calculate the number of keys needed for N parties via symmetric encryption?

Answer 2

(n(n-1))/2

Question 3

What problem does digital signatures solve?

Answer 3

Proving the origin of data.

Question 4

What concepts are needed for the signature process?

Answer 4

Message, public / private key pair, hash function, signature function, signature, verification function.

Question 5

Which 2 procedures are contained within the digital signature process?

Answer 5

Signing
Verification

Question 6

Give the notation for a reversible encryption scheme.

Answer 6

Ee(Dd(M)) = Dd(Ee(M)) = M

Question 7

Give the steps of how a digital signature is created and verified…

Answer 7

1 - Jason runs a message through a hash function to create a digest.
2 - Jason feeds the digest and his private key into a signature algorithm to create a signature.
3 - Jason appends the signature to the original message and sends too B.
4 - B runs the message through the hash function to create a digest.
5 - B runs the digest and Jason’s public key through a signature verification function to verify the signature.