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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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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Benefits of HMAC-based server authentication [migrated]

Context and assumptions: TLS 1.2 or 1.3, server authentication only Client uses HMAC to authenticate itself to the server, using a PSK key Client is a library, not a web browser, which doesn't allow ...
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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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How can I prove "single-use authorization" from multiple parties without revealing identity?

I've been trying to create a distributed authorization protocol where identities are not revealed. Let me explain with an example. Let's assume we have 4 actors, Alice, Bob, Charlie, and Dan. Alice is ...
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IS zk-SNARK not suitable for constructing anonymous authentication scheme?

zk-SNARK was a powerful tool for privacy-respecting e-cash. However, recent years, in the literatures about anonymous authentication scheme, such as group signatures, anonymous credential, blind ...
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Service match-up over encrypted channel by hashing service description and session ID?

I'm trying to set up a 'view anywhere' telemetry service over a WebRTC RTCDataChannel with on one end a browser and on the other end an embedded system using libdatachannel. The encrypted peer-to-peer ...
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Public signature of challenges as authentication

Assuming you trust a client's public signature keys, a simple authentication protocol would be to send a long random string challenge, and get the client to sign it Since most of authentication still ...
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Authentication in Lattice PQC candidates

I am looking into Authentication in lattice cryptography. Specifically in the NIST KEM finalists. I was specifically looking to see if there was a GCM (Galois counter mode) equivalence in the lattice ...
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Algorithm for anonymous but associated communications from a set of verified communicants?

Let's say that I'm selling a product, and I want to get authentic feedback from my customers. However, I have the following two constraints: My customers must be able to give [at least some of] their ...
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What's the difference between H(m) $\oplus$ H(key) and H(m || key) in MAC construction?

We all know that HMAC has the form of $H(ikey || H(okey || M))$. I'm wondering what if we replace the H(okey || M) into H(okey) $\oplus$ H(M)? In other words, is $$H\Big( ikey \mathbin\| \big( H(okey) ...
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AKE using Noise_NNpsk2 vs Noise_NKpsk2

I am working on an implementation based on the Disco library, which itself is based on Noise and strobe framework. The goal is to do bilaterally entity-authenticated key agreement with perfect forward ...
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Why if i change some characters of a Public key on authorizedKeys the login still works

This question is similar to: [1] Why does my SSH private key still work after changing some bytes in the file? But in this case (on Windows) after editing the authorized_keys file and changing some ...
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What is the main difference between anonymous authentication and using an anonymous credential?

What is the main difference between anonymous authentication and the use of an anonymous credential? And when we should use them?
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Authentication tag length and post-quantum security

The recommended hash length for post-quantum security seems to be either 384-bits or 512-bits. 512-bits gives 256-bit collision resistance, and 256-bit security is obviously ideal for post-quantum ...
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HKDF Bit Security

I've always understood the bit security of hash functions to be related to their output size (eg. collision resistance). However, I recently came across a table from a Wickr blog post that lists HKDF-...
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How secure is Encrypt-And-MAC?

From this popular Crypto.SE thread, the general feeling is that Encrypt-Then-MAC is the most secure. From the first answer, the poster says that Encrypt-And-MAC provides integrity of the plaintext. If ...
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Diffie Hellman with Smartwatch

I am trying to reverse engineer the Handshake wit a Smartwatch by sniffing the BLE traffic. There is what I figured out and were able to reproduce: The manufacturer-app requests a random number from ...
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Converting Letters into Numbers for Creating an Authenticator

In Section 2.2 of DJB's Polynomial Evaluation and Message Authentication, he describes the construction of the first provably secure authenticator, which was the work of Gilbert, MacWilliams, and ...
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Is it safe to send a hashed password over HTTPS or what is the most secure method of authentication?

My rudimentary understanding of HTTPS and the Diffie-Hellman key exchange is that the client and server can establish a secured connection by generating the same key based on their private secrets and ...

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