How do we encrypt? Explain modern symmetric cryptography.
Explain the digital signature scheme. Explain the cryptography...
How do we encrypt? Explain modern symmetric cryptography.
Explain the digital signature scheme. Explain the cryptography
tools. What is digital signature? What is steganography? Explain
the protocol for secure communications.
Topic: Encrypt-then-authenticate scheme, Cryptography
Let ΠE = (GenE, EncE,
DecE) be an encryption scheme and ΠM =
(GenM, MacM, VrfyM) be a MAC
scheme.
(b) Prove that Π is unforgeable for any encryption scheme
ΠE (even if not CPA-secure) and any secure MAC scheme
ΠM (even if not strongly secure).
Topic: Encrypt-then-authenticate scheme, Cryptography
Let ΠE = (GenE, EncE,
DecE) be an encryption scheme and ΠM =
(GenM, MacM, VrfyM) be a MAC
scheme.
(a) Formalize the construction of the
“encrypt-then-authenticate” scheme Π = (Gen, Enc, Dec) given
ΠE and ΠM
Suppose we use the ElGamal signature scheme with p = 65539, ? =
2, ? = 33384. We send signed messages (m, r, s): (809, 18357, 1042)
= hi and (22505, 18357, 26272) = bye. (a). Show that the same value
of k was used for each signature. (b). Use this fact to find this
value of k and to find the value of “a” such that ? ≡ ?? (???
?).
Suppose we use the ElGamal signature scheme with p = 65539, ? =
2, ? = 33384. We send signed messages (m, r, s): (809, 18357, 1042)
= hi and (22505, 18357, 26272) = bye. (a). Show that the same value
of k was used for each signature. (b). Use this fact to find this
value of k and to find the value of “a” such that ? ≡ ?? (???
?).
Suppose we use the ElGamal signature scheme with p = 65539,
?=2,?=33384. We send signed messages (m, r, s): (809, 18357, 1042)
= hi and (22505, 18357, 26272) = bye. (a). Show that the same value
of k was used for each signature. (b). Use this fact to find this
value of k and to find the value of “a” such that ?≡?? (??? ?).