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How is a nonce generated?
Types of nonce values A random nonce is produced by stringing arbitrary numbers together while a sequential nonce is produced incrementally. Using the sequential nonce method guarantees that values are not repeated, cannot be replayed and do not take up unnecessary space.
What is client nonce?
The client nonce is there to protect the client against a replay attack. Without the client nonce, an attacker could intercept the initial request for a nonce by CS, and respond with an old nonce that the server used previously.
How does a nonce prevent replay?
There are two ways to prevent replay: First, secure network protocols can require the exchange of freshly generated random strings, or nonces. Old messages cannot contain subsequently generated random data, and will therefore contain the wrong nonces if replayed.
Why is nonce required?
2 Answers. The purpose of a nonce is to make each request unique so that an attacker can’t replay a request in a different context. It doesn’t matter if the attacker gets the nonce: in fact the point is that because the data includes a nonce, it won’t be useful to the attacker.
Do you need to store a nonce in a database?
You can store nonces in any way you want, e.g. in a database; also note that you don’t need to store past nonces longer than their validity time. In fact, a nonce should be timestamped, and valid only during a limited time since its creation.
How big of a nonce do you need to store?
In this case and if the nonce is sufficiently big (say, 12+ bytes) there is no need to check against previous nonces as you will never encounter a repeat in your life. You can store nonces in any way you want, e.g. in a database; also note that you don’t need to store past nonces longer than their validity time.
Is it true that nonce is supposed to be random?
First of all, As nonce is supposed to be random is not, strictly speaking, true. Nonce in general is only required to be unique. It is, however, often convenient to generate nonce as (pseudo-)random bytes.