A "nonce" is an arbitrary number or string used only once within the context of a specific cryptographic scheme. Nonces are used e.g. in authentication protocols to prevent replay attacks, as well as in stream ciphers (including CTR mode) to avoid keystream reuse.

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Why does spiped use both nonces and ephemeral keys?

Colin Percival's spiped utility uses a pre-shared key and Diffie-Hellman with ephemeral keys to provide forward secrecy. The protocol is summarized in the ...
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nonce of AES-GCM in SSL

It seems that the nonce of AES-GCM in SSL has 3 parts: salt, 4 bytes, generated in handshake, not changed in whole session nonce_explicit, 8 bytes, chosen by the sender and carried in each SSL ...
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106 views

credit card number encryption using aes-ctr mode

I want to encrypt credit card numbers. I want to apply AES-CTR mode. Is it suitable for that? How can I store nonce and counter values for an individual credit card number? How can I send the ...
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31 views

Determining nonce between unsynced systems

It's my first venture into cryptography, and I'm struggling with how to use a nonce in an encryption standard between two digital radios. The two radios support AES encryption, only requiring a ...
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42 views

Security implications of public nonce

I'm planning to use the crypto_box() functions of Nacl (or, alternatively, the crypto_box_easy() functions of libsodium) to ...
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1answer
72 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 ...
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56 views

Should the nonce passed to GCM be authenticated?

This answer recommends authenticating the IV with HMAC when using AES and then HMAC. Since AES-GCM provides authentication too, should the external nonce passed to GCM be authenticated separately ...
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1answer
85 views

Security aspects of using a global values as nonce and additional data for AES? [on hold]

is it a good idea to use global values as nonce / additional data? What problems can occur? What should be take in account when we deal with such parameters for encryption. Thanks
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75 views

Nonces being used in SSL and MAC to prevent replay attacks

I'm a bit confused in the way nonces are used in these processes to prevent replay attacks. Heres How I think it works during SSL: Nonces are exchanged during stage one of the handshake protocol. ...
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78 views

Using hash of plaintext as nonce in NaCl secretbox- bad idea?

I need a nonce to encrypt my stuff using NaCl secretbox. I will be transmitting the nonce along with the ciphertext, which I have been told is OK to do. It occurs to me that one could simply use the ...
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47 views

Is there (this) a case in which salting is dispensable?

tl;dr this is not a duplicate of "what is a salt/why use salt?" question. Instead it is specificly asking when salt may not be necessary for hashing securly? (i.e. when the data being hashed is ...
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I don't care about replay attacks. What should I do with the nonce in nacl?

My system forwards encrypted and/or signed messages on a gossip network. Replay is part of the design. What should I do with the nonce? I'm tempted to just set it to the same number always. Is this a ...
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what is SALSA20 Nonce and its requirements [duplicate]

what is the source of nonce in SALSA20 algorithm. basically who provides the value of nonce in SALSA20 algorithm
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Can adding nonces make challenge response authentications weaker?

In a custom protocol we want to replace an aged tiger32 based challenge response authentication. I suggested that we use something existing, so threw HMAC into the room. As per wikipedia it works as: ...
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1answer
75 views

Counter Mode: how to choose the nonce part of the counter? [duplicate]

Suppose: The "counter field" is about: NONCE || CTR-VALUE. I have multiples messages $M_a, M_b, M_c, \dots$ Each message can be divided into x-bits blocks ($M_{a1}, M_{a2}, M_{a3}, \dots$). Each ...
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Streaming mode of operation that is more resistant against nonce reuse

Is it possible to create a streaming mode of operation where the reuse of a nonce does not destroy confidentiality? In this question it would be allowed for the streaming mode to leak if ciphertexts ...
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2answers
222 views

OCB nonce usage

I've just come across this piece of code in Bouncy Castle's implementation of OCB Mode: ...
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454 views

Is there a standard way to use a nonce with HMAC?

Many protocols use HMAC on messages that include a nonce, but they don't seem to do it in a consistent way. For example, in OAuth the nonce is in the middle of an URL-encoded key-value string, like ...
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1answer
117 views

Strategy for random CTR initial counter values

Alice has a secret key which she uses to encrypt messages in CTR mode. CTR mode is critically vulnerable to counter reuse, and Alice has a problem: she has terrible memory and no pen to write anything ...
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Difference between a nonce and IV

I know the generic difference between a nonce and an IV. I am specifically looking for a clarification on these terms as used in the "Evaluation of Some Blockcipher Modes of Operation" by Phil ...
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1answer
358 views

CVE-2014-1295 (Apple's Secure Transport and Triple Handshake Attack)

Apple is releasing some updates today. They have not published the bulletins yet, but they are available here: https://gist.github.com/FredericJacobs/11189734. In the writeup for CVE-2014-1295: ...
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2answers
252 views

IV/Nonce in CTR&GCM mode of operation

We know reusing IV can compromise our secrecy. I have some questions aiming to clarify the use of an IV/Nonce in CTR/GCM: Is it OK to use the same key for encrypting plain-texts in authenticated ...
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1answer
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Why does the crypto_box functionality in NaCl library exposes the nonce to the programmer

The idea of crypto_box API in NaCl library is to shield the programmer away from the technical details and provide an easy to use functions for encrypting and encrypting messages. Given what I've ...
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Making counter (CTR) mode robust against application state loss

Counter (CTR) mode, which is a block cipher mode of operation, has some desirable qualities (no padding, parallel encryption and decryption), but at the cost of failing badly when non-unique counter ...
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CTR mode nonce with aggressive key rotation policy

I'm writing a small encryption library which will be required to use the shortest possible amount of overhead for describing ciphertexts. I want to use CTR mode with a 6-byte random nonce. Normally ...
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2answers
599 views

Encrypted counter as IV in CBC mode encryption using same key

I'm currently working with a secure transport protocol that defines the IV to be a counter (incremental nonce) to be encrypted with the same key. This is a followup to a protocol that did not provide ...
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495 views

AES-SIV security

I am invesigating the AES-SIV (rfc 5297) based block cipher. The construction of the S2V is lying on the AES-CMAC and dbl and XOR operation. Given a AAD the size of L and in the 128bit block ...
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248 views

Why restrict nonce/IV and counter to specific sizes?

When setting up a nonce/IV and counter (e.g. for AES-GCM-128), why are the nonce/IV and counter restricted to specific sections (e.g. random nonce/IV in first 8 bytes and counter in last 8 bytes)? ...
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What are the requirements of a nonce?

Sometimes I read that a nonce has to be a random number but I disagree. A nonce just can't repeat itself. You could increase in by 1 every time if you are sure it would never repeat.
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Is it safe for the ChaCha8 nonce to be deterministic?

ChaCha8 takes a 8 byte nonce (or IV) that should not be the same twice for the same key. Generating this nonce randomly makes me very very nervous for collisions. Is it safe to generate this nonce ...
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Unique GCM/CCM initial counters without recipient side message counters

I am implementing the encryption layer for a communication protocol. The bulk encryption method used is either AES-CCM or AES-GCM. Due to implementation details, encryption of packets is usually, but ...