Week 10: 1
5-2023 NT219–Cryptography
NT219- Cryptography
PhD. Ngoc-Tu Nguyen
tunn@uit.edu.vn
Week 10: Digital Signature
Week 10: 2
5-2023 NT219–Cryptography
Textbooks and References
Text books
[1] Chapter 13.14
Week 10: 3
5-2023 NT219–Cryptography
Outline
Motivations
Overview digital signature process
Elgamal digital signature scheme
Schnorr digital signature scheme
NIST digital signature schemes
RSASSA-PKCS, RSASSA-PSS
DSA, ECDSA
Public key distribution (X.509 digital certificates)
Week 10: 4
5-2023 NT219–Cryptography
Motivations
How to ensure that the message is the original one?
How to verify that a message comes from the claimed
sender? Authentication?
Integrity?
MAC, HMAC
Alice Bob
agree a session key
(using Diffie–Hellman for ex.)
𝑠𝑒𝑛𝑑 𝑀 ?
𝑀,𝑡𝑎𝑔=𝐻𝑀𝐴𝐶
(
𝐾,𝑀
)
=𝐻(𝐾,𝑀)
𝑀
′
,𝑡𝑎𝑔
𝑀=𝑀′
𝐾
𝐾
Week 10: 5
5-2023 NT219–Cryptography
Motivations
How to ensure that the message is the original one?
How to verify that a message comes from the claimed
sender? Authentication?
Integrity?
MAC, HMAC
Alice Bob
If A and B can not agree a session key ?
𝑠𝑒𝑛𝑑 𝑀 ?
𝑀,𝑡𝑎𝑔=𝐻𝑀𝐴𝐶
(
𝐾,𝑀
)
=𝐻(𝐾,𝑀)
𝑀
′
,𝑡𝑎𝑔
𝑀=𝑀′