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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How to use nonces to prevent replay attacks while enabling concurrent requests?

Nonces are often used to prevent replay attacks in networks. Because they are a one time use, any attacker replaying a request would be stopped because the nonce would be invalid. However using nonces ...
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Can asymmetric encryption be used in HMAC, and still ensure the data has not been tampered with? [closed]

Suppose I want to send a message, but not privately; I want everybody to see it, even an attacker in the middle. I would do this by appending a public key to the start of the data, which could be used ...
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Randomness and authentication on short value outputs (48 bits)

I want to implement a client that generates random 48-bit values and send them as broadcast messages. We assume also there is a legitimate receiver getting those values (so, there is some sort of pre-...
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Is it possible to have a Hierarchical Deterministic KD for ECC with child key leak not impacting parent key?

From what I understand, in BIP 32, the knowledge of the parent public key and the child private key provides the parent private key, in a non-hardened path. Indeed, it's only a matter of substracting ...
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Authenticated Diffie-Hellman with no proofs that each one keys are the right keys. Is it possible?

Let's suppose that Bob has only Alice's IP and no more information about Alice's key, nor the digest of Alice's key. They exchange keys and need proof that the received keys are the same keys that ...
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Why EUF-CMA without verification oracle is not equivalent to EUF-CMA with verification oracle?

In the book we have talked about sEUF-CMA-secure with verification oracle being equivalent to sEUF-CMA-secure without verification oracle. The proof idea is simple. One direction is trivial. The other ...
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Is CMAC secure without IV and the same key? (authenticate only)

I am a bit unsure about CMAC and GMAC and maybe someone can help me. As far as I know, CMAC does not use an IV [SP 800-38B ch. 6.2]. Is it then secure if I use the same key for different messages? ......
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Public key cryptography for logins

This is a question sparked purely by curiosity, wanting to understand a little more about cryptography and authentication. Thanks in advance to anybody taking their time to answer. Instead of salting ...
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Is this authentication protocol secure against both eavesdropping and server database disclosure?

Consider the following protocol from the book "Network Security: Private Communication in a Public World" by Kaufman et al. Alice knows a password. Bob, a server that will authenticate ...
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How does PUF authentication work?

I understand that PUFs (physically unclonable functions) produce unique output based on challenge input because of their sensitivity to manufacturing differences, but not how the actual authentication ...
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How does birthday attack on message authentication work?

In Cryptography Engineering: 2.7.1 Birthday Attacks Birthday attacks are named after the birthday paradox. If you have 23 people in a room, the chance that two of them will have the same birthday ...
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How does biometric authentication add protection to encryption schemes?

I'm wondering since at least 2 offline password management services,Passkeep and Keepass both use biometric authentication in addition to the master password. You need to possess the physical device ...
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How to ensure files on client computer haven't been tampered with by client?

I'm designing a program that clients can download to the computer. This program needs to sync with my online server on a regular basis to confirm that the client's Activation Code hasnt expired and ...
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IKEv1 Phase 1, authentication with signature, sending certificates "optionally"

At RFC2409, section 5.1, authentication header is like: HDR*, IDii, [ CERT, ] SIG_I HDR is an ISAKMP header whose exchange type is the mode. When writen as HDR* it indicates payload encryption. IDii ...
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Is there a way to "tag" a key in a way that prevents it from being reused?

Say I have a pair of public and private keys associated with some resource (e.g. a TLS certificate for a website mycoolsite.com). I am free to take those keys and reuse them for a different resource (...
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Is it possible to prove possession of AES-128 key?

My question is kind of related to this topic: Can we prove possession of an AES-256 key without showing it? But I couldn't figure out how to apply it to my problem. Description: Lets say I have a ...
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Proving to a 3rd party an email received in a@domain2.com was truly sent from a@domain1.com

Example: I send an email from address@domain1.com to address@domain2.com Using only the email I received in address@domain2.com, I'd like to prove to a 3rd party that I also own address@domain1.com ...
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Does CMS AuthEnvelopedData type provide message authentication?

I was looking through the S/MIME Message specification (RFC 8551) to find out what security services it offers. Section 2.4.4 of this document describing AuthEnvelopedData content type (which uses the ...
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Hybrid Authentications

Is there a reason why we can't combine private key MAC with digital signature to get a hybrid authentication scheme? Is it because of the computational assumptions that digital signatures have? Edit: (...
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Can we encode with the set of $\{0,1\}$ and its Boolean operations any finite or infinite domain?

Can we encode with the set of $\{0,1\}$ and its Boolean operations any infinite domain that is subset of the real numbers $\mathbb{R}$ or the whole set of real numbers? For example can we encode the ...
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How is MitM attack prevented when complete session is hijacked?

Lets say there is mutual authentication between a client which connects to a server on an otherwise unsecured TCP channel. Both parties create a random challenge and the other side answers with a keyd-...
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Is this kind of mutual Authentication safe?

The following is a real-world problem. In a standardized protocol clients can connect to a server using mutual 4-pass authentication on an otherwise unsecured TCP channel: pass-1: Client send random ...
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Should I use HMAC to create a multiple part HASH token

I have a web API with a custom API authentication system that users each have a SecretKey and a public ApiKey. Using these two keys client(or user) can generate a token for the authentication on the ...
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How to securely store data with an untrustworthy party?

Alice wants to store key:value pairs with Bob. The goal of the exercise is for Alice to be able to use Bob as a reliable data storage service, even if Bob were ...
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What is the link between anonymous credentials and transactional pseudonyms?

Anonymous credentials are used to prove certain properties of a specific user without revealing any other information, and transactional pseudonyms are used to authenticate a user as the rightful ...
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mutual authentication in STS protocol

STS Protocol is like this: $A \rightarrow B:~ g^x$ $A \leftarrow B:~ g^y, E_K(S_B(g^y, g^x))$ $A \rightarrow B:~ E_K(S_A(g^x, g^y))$ My question is why do we say in STS we have mutual authentication?...
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Understanding MITM in an example authentication protocol

Imagine that we have a protocol like this: B -> A: RB A -> B: {RB,B}K Goal: authenticate A to B K: a shared key between A and B {}K: encrypting by K After receiving {RB, B}K by B, B is able to ...
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What if the other user generate the Session Key rather than KDC for Key Establishment

I m studying for the Key Establishment Using a Key Distribution Center From my understanding, KDC contains all the users' private keys. For example, If Alice wants to talk with Bob, Alice requests to ...
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how high is the possibility of getting a hash collision in text files?

Just for an example, let's say I downloaded "the adventures of tom sawyer" from gutenberg in .txt file format and saved it to my usb thumb drive. And as you can see, usb drive is not an ...
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Can I use SHA256 from BIP39 passphrase for auth credentials?

I am working on an E2E encrypted app. I am using OpenPGP.js and storing public and private keys on the server. The private key is encrypted with a BIP39 passphrase which is stored in browser ...
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Do I need to change IV in AES-256 GCM when I only use encryption for challenge-response exchange with random string?

When I want to use encryption only for challenge-response exchange and not for hiding the contents of an encrypted message, is it still a threat to me not changing IV for new encryption? For easier ...
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Is it safe to use AES-CCM only for authentication - i.e. for sending AAD without encrypted data?

We are employing an AES-CCM 128-bit stream-cipher with 7-Byte Nonces and 12-Byte Authentication Tags in a communication protocol. Up until this point there was no need to use Additional Authenticated ...
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Hashed password used for encryption and for user authentication at the same time

As I am fairly new to cryptography, I would like to understand how to, in a simple way, implement a system that would achieve the following: the user would have to setup a password, which would then ...
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Authentication in P2P networks without central server

I'm trying to understand how to perform authentication in an P2P network without a central server. Given a network with no central trusted unit and a PKI, how can one be sure of the authenticity of ...
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Digital signature with Big Brother

I have read digital signature with Big Brother but don't understand the sequence. One approach to digital signatures is to have a central authority that knows everything and whom everyone trusts, say ...
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Is the collision chance 2^(n/2) of an n-bit tag τ unchanged if reduced to (n/2)-bits using a reduction of τ to some 2^(n/2) order group element?

If $H(k, Μ) = τ$, in the context where $τ$ is an $n$-bit tag produced as a mac on a key, $k$, and a message, $M$, through a keyed-hash function, $H$, is there a function $F(τ) = T$ that transforms $τ$ ...
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Authentication between two servers using PKA

I've run into an small issue regarding authentication between 2 services (One way communication) using public and private key authentication (Elliptic Curve, secp256k1). The services will communicate ...
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Is server-side password strength validation possible with client-side password hashing?

Let's say I wish to setup a classic username & password authentication strategy on a server. All communication is encrypted via TLS. But ideally, I still do not want the server to be able to read ...
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Ensure that a speedrun (or video recording) was done in one continuous hop (and not spliced together from many parts)

In speedrunning video games, one records a game being played and beaten in one continuous attempt. However, what can be done to cheat is to do multiple attempts, and splice together clips of the best ...
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Authentication by Presenting the Symmetric Key over an Encrypted Channel

I have devices which need to communicate with a server over a mutually authenticated and encrypted channel. Authenticating the server is relatively easy, since I can embed the CA certificate in the ...
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Designing a CRAM protocol for mutual authentication in constrained devices

We are currently designing a simple Challenge-Response Authentication Mechanism (CRAM) protocol based on symmetric cryptography that would be used on the constrained embedded devices that would ...
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Is there any “approximate or probabilistic” password authentication method?

I understand that the password-based authorization check procedure requires that you enter a password that is correct, that is, does not allow even a single bit difference. Suddenly I have this ...
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Authenticating Infrastructure SOAP-based API

I have been involved in a discussion the other day regarding the implementation of backend-to-backend authentication. The communications between each backend happen via SOAP (XML) message protocol. ...
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Mifare Classic, authentification protocol question

Thanks to reverse engineering papers on Mifare Classic, one can study the authentication protocol. However, I have a problem understanding how it works. In the above document, after the reader ...
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Using shared secret as Out-Of-Band authentication data in Bluetooth pairing

According to the Bluetooth Specification, the pairing process starts with Slave sending a connectable advertising packet and then the Master initiates the connection. In LE Legacy OOB authentication a ...
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Impact of partitioning oracle attacks on file encryption?

I've just learned about partitioning oracle attacks recently, and I would like to clarify some things that are a little foggy to me right now. According to this thread, The aim is the recovery of a ...
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Consequences of P=NP for Authentication

Let's suppose that P=NP. That is, every problem whose solution can be quickly verified can also be solved quickly, regardless of what that means at a formal level. So, not only does P=NP, but there ...
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Encryption of small data with fixed key and incremental IV

I have a Bluetooth device that sends a small package periodically (without receiving). I want to encrypt and authenticate the data using AES-128. It has an embedded random and unique key which is ...
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How to compose multiple values to MAC authenticate?

If the data I want to authenticate consists of multiple values and I compute a MAC simply concatenating the values, an adversary can "shift" characters within those values without ...
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Is it possible to allow a user to log in if logged out without identifying them?

I have to verify that the user has registered and is currently logged out without identifying the user. Essentially, I am looking for privacy-oriented authorization mechanisms which prevent ...
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