Questions tagged [authentication]

Authentication is successfully validating that an entity you are communicating with is actually who they claim to be. The entity typically demonstrates who they are by showing they possess a secret that only they could know.

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1answer
159 views

Authentication and integrity

I was trying to solve this problem: Sometimes Alice needs to send a file to Bob, guaranteeing her identity and the file integrity (no confidentiality required); the two parties are sharing a secret w ...
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What is the point of using a cryptographic sequence number if you're not using it as a nonce?

OSPF features the use of Auth Crypto Sequence Number however, from reading the RFC it would appear the sequence number is not being used as a nonce. In addition, ...
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Generating secure short activation code for offline applications

My application is as follows User has a hardware system (with an unique ID) that does not have connectivity but has a keypad for input. To make the hardware operational, the user has to go to central ...
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shared symmetric key

Suppose $R$ is a random challenge sent in the clear from Alice to Bob and $K$ is a symmetric key known only to Alice and Bob. Which of the following are secure session keys and which are not? Justify ...
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Attack on challenge response protocol using shared symmetric key and addition of random nonce [closed]

Consider the following mutual authentication protocol, where KAB is a shared symmetric key. Give two different attacks that Trudy can use to convince Bob that she is Alice.
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What can I do, if my SRP password verifier was stolen?

I've got a system that works like this: ...
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Password vs public key for authentication?

What's the difference password and key in terms of authentication? I think that they are potentially same. But, in practice, password involves some bias since it is created by human. On the other ...
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224 views

Encrypted Hash vs MAC [duplicate]

I (believe I) am aware of the general difference between a hash and a MAC; the former is used for integrity and the latter for integrity and authentication as it also takes a secret key as an input in ...
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Authentication scheme to protect against fake devices

I want two embedded devices (call them master and slave) to communicate with each other. For intellectual property protection, the master must reject fake slave devices (the other way around is a pre ...
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Why is this authentication protocol with a nonce and tree parties not secure?

Why is the following authentication service not secure? C⟶S: $I_C$ S⟶C: $N$ C⟶S: $E(K_{C,A}, N)$ S⟶A: $E(K_{S,A}, \{I_C, E(K_{C,A}, N)\})$ A⟶S: $E(K_{S,A}, N)$ where: C = client S = server A = ...
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Is authentication more computationally expensive than encryption?

newbie in crypto here. I've a application that needs integrity protection. Confidentiality would be nice but has less priority over performance throughput. So I test "openssl speed" on my laptop, and ...
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merkle tree motivation

Here author seems to give overview of merkle trees. However, I have one problem. As in the article author claims you can use merkle trees to verify authenticity of data, e.g. if piece of data is ...
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Why exactly is a root hash used in relation to hash lists?

Wikipedia has an rticle about hash lists, although I find it technically not very detailed. For example: We could solve same problem by sending (authenticated) hash of each data block, together with ...
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216 views

ABE (attribute based encryption) vs ABS (attribute based signature)

I want to know if there is any shortcoming that ABE cannot achieve and that the ABS complete it. I mean why the ABS is included if the authentication and the authorization are already ensured by the ...
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PKI Challenge Response: why is $h(r) = x$ enough to protect against chosen text attacks?

I think the question was asked somewhere else but not answered very precisely. Quoting from the "Handbook of applied cryptography": Identification based on PK decryption and witness. Consider ...
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How does the authd protocol work?

So far, I have been able to research on what it is: authentication; authorization; using resource authd. I still have not come across a definitive answer or ...
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Plausibly deniable authentication for agents on multiple teams

Here's a problem that I've been thinking about: An individual, Alice, wishes to authenticate herself. She may wish to authenticate to Bob (who is on the blue team) that they are both on the blue team....
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Any Idea on this identification scheme's problem?

I was looking at the exercises of Cryptography theory and practice and I could not find the answer to this question anyone has an idea?
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Is symmetric encryption with a key containing the userId passes as authentication?

The scenario: There is a web application where ownership check is time expensive so during the development all users were able to access all other user's objects (let's say apples) by changing the ...
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Primitive root in a finite field

Wen-Her Yang and Shiuh-Pyng Shieh proposed two password authentication schemes by employing smart cards, one is timestamp-based and the other one is nonce-based. Their scheme consists of 3 phases: ...
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SCRAM Iteration Count Attack

I'm not sure if this questions belongs here or in the Information Security Stack Exchange, but here goes... With SCRAM (RFC5802), is there anything that prevents an attacker masquerading as the ...
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One-Time MAC's data block length and q

When 128-bit long data blocks are unavailable for one-time MAC: Could 64 bits be used instead? Should $q$ then be >=64 bits? E.g. $2^{64}+5$ Can this be scaled even further downwards to 32, 16, … ...
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Understanding the big picture with regard to how anonymous credentials work

I'm trying to learn about anonymous credential systems. I started with Lysyanskaya's thesis, which gives an outline of how to build an AC system given some particular primitives (signature scheme, ...
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Is it possible to personalize eToken PASS?

I am wondering if it is possible to personalize an eToken to PASS with the following method: On the server side we configure a physical device eToken to PASS when it belongs to Mr. Bob. So when he ...
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Possibility to combine keys for asymmetric signature creation

There is an asymmetric algorithm which signs with a private key and verifies with a public key. Private and public keys are created in pairs. Assume we have 2 pairs of private and public keys. Is ...
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CBC-MAC 8 octet ICV compatable with 16 octet block size?

I'm trying to use DTLS in Preshared key mode for CoAP which necessitates using CipherSuite TLS_PSK_WITH_AES_128_CCM_8 I'm trying to start with the CBC-MAC but I'm not sure how to get an 8 octet ICV ...
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What is the benefit of zero knowledge identification (Fiat Shamir) over a standard digital signature?

Let's say there is a public key $v$. Peggy has to prove to Victor that she has the corresponding private key $a$. Of course she doesn't want to disclose $a$ to Victor, but just to prove that she has ...
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understanding NTLM authentication

The flow is like this. Client sends GET to Server Server responds with 401 UNAUTHORIZED and the authentication protocol: NTLM Client re-sends the request including authentication information. I don'...
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Diffie-Hellman based password challenge response scheme

A very commonly used (examples: HTTP digest auth/CHAP/Kerberos) authentication scheme is something that looks like: Setup. Client and server both know a password $p$. Authentication. Server sends ...
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Why not generate the authentication key from the key and nonce in GCM?

In Galois/counter mode, the authentication key $H$ is leaked if two distinct messages are encrypted using the same nonce. If someone did end up doing that, then they would need to rekey to get a new $...
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RSA public key verification based on a secret

I'm attempting to develop my messanging app with encryption evolved. For now I came up with algorithm for authorization and message exchange. P.S. conneciton between server and client is over https ...
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Why would we want parallelizable authentication?

I believe that parallelizable authentication schemes are superior from an aesthetic perspective and because most non-recursive calculations (e.g., CTR, ECB, PMAC, etc.) are better than recursive ones (...
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152 views

mutual authentication using MAC

I have the following protocol for mutual authentication ($V=$ verifier, $P = $ prover, $r_V$ and $r_P$ random values, $h_k$ a keyed hash function) $V\rightarrow P:r_V$ $P\rightarrow V:r_P,h_k(r_V,r_P)...
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How much less secure is an algorithm that gives feedback that the password is one character off?

If we had a stupid login procedure (SLP for short) like in this comic; it gives feedback on login, if the submitted password is one character off. Would a longer password be less secure? What would ...
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Is using ECDSA with AES-GCM viable?

I'm pretty new to the whole cryptography scene, so please forgive me if I make any incorrect statements. I have a 16MB image that I'm encrypting and authenticating using AES-GCM. I obtain a 16MB ...
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Attribute Authentication in Attribute Based Encryption (ABE)

When a data user requires access it asks the key issuer to generate a key for it using the specified attributes. How does the key issuer authenticate that the data user actually acquires the ...
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Why are finite groups used in cryptography?

Most of the cryptographic schemes I know are all based on group theory, e.g. they use finite groups. Can someone explain why is that the case? And why not base the schemes on elements and operations ...
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Why is SIV a thing if MAC-and-encrypt is not the most secure way to go?

The question that I am asking is exactly what I ask in the title.
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Does ElGamal authentication exist?

Are there any natural ways to transform ElGamal encryption system or ElGamal signature scheme into an authentication protocol?
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Security implications of using hash as a MAC

What are the security risks, if I use a hash function $H$ such that $Y=H(K||M||N)$ where $K$ is a secret key, $M$ is a message, $N$ is a nonce and $||$ is concatenation operation (where the length of $...
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Authentication over the phone?

Are there any known good methods of performing authentication over the phone in a way that's not susceptible to replay attacks? The specific scenario that comes to mind is having an automated call ...
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Should the identity of a sender be verified using additional means, or does a MAC suffice?

This question is aiming at clarification related to message authentication codes (MACs). Wikipedia’s Message Authentication Code article states: In cryptography, a message authentication code (MAC)...
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Security of Carter-Wegman polynomial authenticators, and their concatenation?

Carter-Wegman polynomial authenticators For a given finite field $(\mathbb F,+,\times)$ of $f$ elements, define a Carter-Wegman polynomial authenticator for a message $M=m_1\|m_2\|\dots\|m_l$ of $l$ ...
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What are the different uses of MAC and Digital Signature?

I know both of them can be used for Integrity and Authentication. In which practical cases is preferred a MAC? and a Digital Signature? Thank you in advance
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Use signed email as method for deriving encryption key

I'm trying to create a solution to decrypt a file at rest on a server by sending an email to a given address and receiving a reply from that address. I'm struggling to see if its possible and haven't ...
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Changing password hash and iv on (successful) user login

I've implemented a system for my login page (with php) that will update the password hash and initialization vector (for openssl) on each login. So essentially, every time the user successfully logs ...
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How many bits should a token have to be unguessable (given some computational resources)?

If an attacker may try 10 billion (1E10) random numbers per second. And its attack can last 500 years (500*365*24*3600 = 1.5768E10 seconds). Then the attacker will try 1E10*1.5768E10 = 1.5768E20 ...
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SRP with random, but constant private-value b

In RFC5054, the SRP6a algorithm states that the client and the server should generate random ephemeral private values $a$ and $b$ respectively which are used for further derivation in the handshake ...
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Transferable ownership certificate

Is there a crytpographic way to assert ownership of an asset (let's say a piece of stone)? As an example, a number (public key) could be engraved in the stone, and the owner could keep a private key (...
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Rivest's ring signatures with hashes instead of symmetric encryption

While studying ring signatures, I obviously stumbled on the Wikipedia article about ring signatures. It includes a piece of Python code to demonstrate "How to leak a secret" ring signatures. ...