a random number that is only used once. It is generated at the beginning of a communication by one communication partner and has to be sent back by the other one in order to prevent replay attacks.

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3
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0answers
54 views

Why isn't Amazon using a NONCE for REST Authentication?

When you look at Amazons RESTAuthentication you can see that it doesn't use a nonce: Authorization = "AWS" + " " + AWSAccessKeyId + ":" + Signature; Signature = Base64( HMAC-SHA1( ...
0
votes
1answer
54 views

How does (Py)NaCl work exactly?

At the moment, I deal with PyNaCl (Docs) and have a question about it: My situation is that I want to create a server that interacts with clients. Both the server and the client will have a long-term ...
1
vote
1answer
29 views

Is it ok to append the nonce/iv to the ciphertext when using AES GCM?

I want to use AES GCM to encrypt data at rest. When retrieving the data, I want to make sure that the key is valid and the data has not been tempered with. Can I store the nonce/iv along with the ...
3
votes
1answer
88 views

Replay attack example for validating nonce?

I am trying to validate a JWT token received from Windows Azure. I am following the documentation here: https://azure.microsoft.com/en-us/documentation/articles/active-directory-v2-tokens/#validating-...
1
vote
1answer
27 views

Synchronized nonce

If two parties (Say A and B) have a shared secret key (K), is there any way for each party to use the shared secret key to generate nonce(N) sequence which is equal on both sides without having to ...
1
vote
2answers
825 views

Purpose of nonce validation in OpenID Connect implicit flow

The OpenID Connect specification requires implicit flow clients to generate and validate a nonce: String value used to associate a Client session with an ID Token, and to mitigate replay attacks. ...
1
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1answer
54 views

Generation of a shared nonce that cannot be pre computed [closed]

Is there any system out there currently, which can generate a nonce, which all nodes on a distributed network can agree and calculate the same nonce at the same time, but one an attacker cannot pre ...
2
votes
3answers
158 views

Verify password hashed with nonce when the password is already hashed on the server?

I found this picture in the Wikipedia nonce article: To avoid sending the password in clear text and prevent replay attacks, the password is hashed together with one random number from the server (...
0
votes
1answer
69 views

libsodium nonce and captcha validation

so, I want to implement server which validates registration with captcha. First I thought about storing captchas in a server, but then I thought it would be hassle on caching, memory, what if I need ...
2
votes
1answer
54 views

Risk associate with nonce and hash found in url

I have came across a url with nonce and hash in placed which is an account activation link sent via email. The example is as followed: http://example.com/competition/?r=user/activateaccount&...
1
vote
2answers
233 views

how to store and retrieve nonce in practice

As nonce is supposed to be random and used only one time, when receiving a nonce, I need to check it with all past nonce records. That means I need a database to store every nonce I had before. Of ...
2
votes
3answers
223 views

How to create a secure nonce for WSSE

I need to connect to a REST API using a WSSE header for authentication. Since WSSE still uses the weak SHA1 I believe a good nonce is important. I found very different implementations: * http://www....
1
vote
1answer
42 views

how to test for csrf if the web application is not using tokens and there are no users defined for that application?

I am testing an application that doesn't use anti-csrf tokens for its requests. There are no users defined for this application as well. Well, in that case, how to carry out testing for csrf in this ...
1
vote
1answer
406 views

Login from a desktop application to a web application

I have a desktop application and a web application. The user is loged in on the desktop application. With a click on a button or something the browser should open and the user should be logged in. ...
13
votes
3answers
2k views

Why does the SSL/TLS handshake have a client and server random?

In the SSL handshake both the client and server generate their respective random numbers. The client then generates a pre master secret and encrypts it with the server's public key. However, why can't ...
2
votes
1answer
152 views

3rd Party Authentication protocol

I have a hardware device (H), phone (P) and web server (S). I would like P to be able to send commands to H, but only if it is authorized to do so. Permissions are stored on server. Technically I ...
2
votes
1answer
145 views

Is it necessary to encrypt nonce in cryptographic communication?

Server and client have a pre-shared key K. Assuming that that pre-shared key is safe, so nobody other than server/client can encrypt/decrypt. Client sends a nonce N to server, server then sends back ...
0
votes
2answers
817 views

HMAC: How unique does a nonce need to be if the Date is also part of the signature?

In a HTTP scheme where the HMAC-SHA256 signature is sent as part of the Authorization header, and the message input contains: The request method URL Post data Nonce Date HTTP header How unique ...
-3
votes
1answer
216 views

Authentication protocol based on hash function [closed]

Is it possible that Alice can authenticate Bob without using any secret information except her password, i.e they don't share any thing else. If so, how can I authenticate Alice and ensure the ...
4
votes
2answers
2k views

What's the point of the nonce in CTR mode?

Does having a nonce in CTR mode actually improve security (vs. just using 1, 2, 3, etc. - basically a constant nonce of 0)? As far as I can tell, the best-case scenario security-wise is that the ...
9
votes
1answer
952 views

Is it possible to implement a nonce without storage?

I am looking at implementing an authentication module using OAuth 2.0 Client and I am trying to avoid having any server state. I was going thorough a few other questions when to use nonce? Is it ...
4
votes
2answers
2k views

nonce in SSL/TLS 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. Why do we need the unix timestamp? As the ...
9
votes
3answers
934 views

According to RFC 5246, are nonces in TLS useless (in terms of security) and if yes, why aren't they only random data?

I know the common usage of nonces in security (which is well described in this topic). However, when checking the SSL/TLS protocol, we can notice, according to the RFC, that nonces as ClientHello....
2
votes
1answer
186 views

IKEv2: Why is it important “that each side sign the other side's nonce”

I am currently diging deep into the IKEv2 protocol. In the description of the Authentication (RFC5996, p. 48), the following statement is given: "It is critical to the security of the exchange that ...
1
vote
3answers
94 views

Secure Custom Registration Links

I'm working on a website that allows a current user to invite another individual to be friends by typing in the non-user's email address. The non-user would then receive a custom registration url by ...
1
vote
1answer
554 views

Is this where a nonce comes into play?

I'm reviewing a website a friend developed, and was looking for general errors and concerns. In reviewing I noticed he is very heavy on ajax calls using JSON to a RESTful API that he maintains on a ...
1
vote
2answers
664 views

Is it safe to use Diffie-Hellman public keys as nonces to protect against replay attacks?

I have an interesting case regarding protection against replay attacks. Under the assumption that Alice and Bob have used Diffie-Hellman key exchange to establish a secure temporary session, would it ...
0
votes
1answer
337 views

How to use a token to differentiate between a valid logged in user and an attack?

Let us take the example of my already being logged in to, say, LinkedIn. When I access LinkedIn on a new tab, it automatically logs me in (using cookie info). Now, suppose I visit a forum and through ...
2
votes
1answer
365 views

Is it insecure to ask for the current nonce from server?

I'm developing an embedded application that delivers information through HTTP to my web server. These deliveries are secured by a hash H(secret : data : nonce) where the secret is shared between ...
6
votes
3answers
2k views

How can salted, hashed password storage be combined with a plaintext, nonce and hash based authentication?

My understanding is as follows: To securely store a password (e.g. in a database), you use a hashing algorithm designed for this purpose (designed to be slow, e.g. bcrypt), and you use a unique salt ...
7
votes
1answer
389 views

Encrypting short identifiers?

I am developing a webapp that does not reveal record count, because it hides the primary key. I am looking for a better way to do this. My favorite idea is to encrypt the ID itself with a block ...
6
votes
1answer
1k views

Prevent cross domain form submission with nonce?

I haven't done much in web security before but am now in need to prevent a form from being submitted from anything but my own domain. I know how to lock this down in an .htaccess file but the ...
3
votes
1answer
507 views

Are man-in-the-middle attacks against p2p systems realistic?

I'm implementing a DHT based on Kademlia following this paper. The protocol described in this paper uses nonces to protect against man-in-the-middle attacks. The disadvantage is that latency gets ...
5
votes
2answers
2k views

Do Client Nonces enhance the security of HTTP Digest Auth?

As far as I understand the answer at http://security.stackexchange.com/a/3024/13447, client nonces are meant to prevent attackers from amortizing the costs of brute-force hash computations by being ...
9
votes
2answers
7k views

when to use nonce?

I have trouble understanding nonce. I read a very good answer related to nonce by @Thomas Pornin, but it is too complicated for me as I am new to cryptography. From what I know, nonce is used to ...
5
votes
3answers
3k views

optimal way to salt password?

A good way to salt password? I have read a few answers related to salting password. But I started to get confused. I came across few functions people used to generate salt like: mcrypt_create_iv() ...
22
votes
2answers
9k views

When using AES and CBC, is it necessary to keep the IV secret?

If I encrypt some data with a randomly generated Key and Initialization Vector, then store all three pieces of information in the same table row; is it necessary to encrypt the IV as well as the Key? ...
8
votes
1answer
2k views

Is it possible to have stateless server nonces in HTTP Digest

When implementing a HTTP Digest server, there's the issue of nonces. Server nonces (as opposed to client nonces) must be issued by the server may be re-used by clients as long as the server allows ...
1
vote
3answers
978 views

Three Message Authentication Protocol

I have a protocol where "A" initiates communication with "B". "B" then sends a challenge to check if "A" is really "A". "B" does not remember sending the challenge so "A" has to respond by sending the ...
6
votes
3answers
1k views

chosen plaintext attacks against MD5 and SHA1

According to http://tools.ietf.org/html/rfc2617#section-4.9, having the server chose a nonce but not having the client chose a nonce opens up Digest Access authentication to chosen plaintext attacks. ...
1
vote
1answer
763 views

Nonce construction for CTR mode (Mcrypt)

Edit: I'll put up this more clearly. By the most simplest form, I'm asking that if I AES encrypt in CTR more with Mcrypt (using PHP), can I create the "IV" by just simply reading 16 bytes from /dev/...
9
votes
1answer
4k views

SSL replay attack when client/server random is missing

Hey studying the SSL protocol, I'm wondering how can someone be able to do a replay attack if the server nonce is missing? All the material I find says that nonces prevent it, but theres no examples ...
51
votes
4answers
25k views

What is the use of a client nonce?

After reading Part I of Ross Anderson's book, Security Engineering, and clarifying some topics on Wikipedia, I came across the idea of Client Nonce (cnonce). Ross never mentions it in his book and I'm ...
11
votes
1answer
3k views

TLS replay attack - requirements of the serverHello nonce

As you all know, the SSL/TLS protocol requires both client and server to exchange (in clear text) a random number or nonce. This is presumably used to prevent replay attacks. It is not clear to me ...
21
votes
3answers
7k views

How long should a random nonce be?

NIST provides good guidelines on the length of keys and hashes for various algorithms. But I don't see anything specifically on the length of a random or pseudo-random nonce (number used once). If ...