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What is the purpose of nonce?
Definition(s): A random or non-repeating value that is included in data exchanged by a protocol, usually for the purpose of guaranteeing the transmittal of live data rather than replayed data, thus detecting and protecting against replay attacks.
What is the purpose of the client and server random nonces in the TLS handshake?
The server has its own random number that it sends during the handshake, and the server’s random number protects the server from replay attacks, so there’s no need for this. (The client also sends a random number, which protects the clients from replays. So, both endpoints’ interests are protected.
How does nonce prevent replay attack?
Nonce is a randomly-generated, cryptographic token that is used to prevent replay attacks. Without nonce, when a UsernameToken is passed from one machine to another machine using a nonsecure transport, such as HTTP, the token might be intercepted and used in a replay attack.
What is nonce value?
A nonce is a random or semi-random number that is generated for a specific use, typically related to cryptographic communication or information technology. Typically, a nonce is some value that varies with time, in order to verify that specific values are not reused.
Is there a ” client nonce ” in SSL / TLS?
There is no “client nonce” in SSL/TLS. There are some “used only once” numbers created by the client, like the IV for the symmetric encryption or the “client random” for the TLS handshake. In the following I will assume that you mean client random instead.
What is a nonce in a SSL handshake?
In SSL/TLS handshake, a nonce is always sent by the client to server and vice versa. The nonce basically consists of a random number and unix timestamp.
How does the client send a nonce to the server?
The client initiates a connection to the server. The server generates and sends a nonce snonce back to the client. The client generates another nonce cnonce, and sends it plus a hash of its credentials, the server nonce and the client nonce ( hash (snonce + cnonce + password)) to the server.
How does the nonce help protect the client?
Here the client nonce acts as a salt for the hashed password. The client nonce also contributes to protect the client from a badly implemented server. Suppose the server did not generate a random nonce but instead a constant that Mallory could easily find by observing traffic.