Key-Hashed Message Authentication Codes or HMACS
What is Key-Hashed Message Authentication Codes or HMACS?
Expert
Digital signatures provide message-by-message authentication, as well as message integrity. Unfortunately the use of digital signatures requires that parties have a public/private key pair and that a secure mechanism for distributing public keys exists. There is also overhead for computing the digital signature, since slow public key encryption is used. Because of these shortcomings another approach to message-by-message authentication is often used - key-hashed message authentication codes. This approach requires that both parties share some secret information, usually a symmetric key. Most cryptographic systems, systems that provide authentication and confidentiality, provide this. The process involves appending the secret shared information to the message and then computing the hash, which is called the HMAC. The HMAC is sent with the message. The receiver recalculates the HMAC from the plaintext part of the message using its own copy of the shared secret information. If the calculated HMAC is equal to the received HMAC, the message is authenticated.
The advantage of using HMACs is reduced computation and not needing to maintain a public key infrastructure. However, HMACs do not provide for non-repudiation as both sides know the secret shared information and the receiver could construct a HMAC for a message that the sender did not send. Digital signatures must be used if non-repudiation is required.
State what are the trailers and header and how are they generally added and eliminated?
How does OSPF find out an inter area shortest path?
Explain the term GPRS or General Packet Radio Service?
How does WSDL describe a web service? Illustrate your answer with the WSDL contract given in the lecture.
Name the two protocols which are mainly used in the Java RMI technology?
Describe the reasonable expectations for the VPN? Briefly state the expectations?
4 channels, two with a bit-rate of 300 kbps and two with a bit-rate of 250 Kbps are to be multiplexed employing multiple slots TDM with no sync bits. a. Find out the size of a frame in bits? b. Determine frame rate? c. Compute the duration of a frame? d. Find out the data rate?
Which among OSI layers are network support layers?
What is meant by the term data communication?
Explain why Bluetooth 2.0 is much better?
18,76,764
1924384 Asked
3,689
Active Tutors
1427918
Questions Answered
Start Excelling in your courses, Ask an Expert and get answers for your homework and assignments!!