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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Client authentication: only talk to trusted clients?
As a preamble,I acknowledge that it is fundamentally impossible to authenticate
that a networked client is who they claim to be. The question is, given that
it's impossible, what should I do anyway?
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Shamir Secret Sharing for API Authentication
I want to implement authentication for an API and thought about using Shamir Secret Sharing to do so.
My plan is to generate 1 Master Key which is stored in the Database, we then generate about 1000 ...
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Regarding the Digital Signature Algorithm During Client Authentication in TLS 1.2
In TLS 1.2, when client authentication is carried out, digital signatures are utilized. However, at what point is the specific signature algorithm communicated to the server? It seems to me that the ...
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Safe implicit value validation: $H_k(k \oplus m) \sim H_k(m)$?
$H_k$ is a cryptographic hash function that's keyed using a section of key material $k$ (for whatever definition of "keyed" that's appropriate for the given hash function $H$).
Are the ...
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Authenticate the users (in telegram bot) without storing user ids
Might be a bit weird but interesting scenario: I have a telegram bot and I need to authenticate users but I don't want to store any user data(at least openly).
So here's a breakdown:
I need to prove ...
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Reason for two random numbers in DSA?
Why is the signature in DSA the way it is?
I am referring to $r$ and $k$ in the Signing-Algorithm depicted below. Is it really necessary to have both, $r$ and $s$, or would it still be secure if only ...
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What is the use of Secure Protocol Data Management (SPDM)?
By going through the document: https://www.dmtf.org/sites/default/files/standards/documents/DSP0274_1.2.0.pdf
I could get that this spec will be used to verify the identify and attestation of h/w &...
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How two secure elements can safely authenticate each other without a third party?
Assume there are multiple secure elements, and also multiple man-in-the-middle or malwares. How can any two secure elements authenticate each other without a third party and hard coding something in ...
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Tag Management Problem in Authenticated Disk Encryption
1) For authenticated disk encryption, there are extra data such as IV or tag that need to be stored for all the alternative mods that are placed in Table 1. For these data, it will be necessary to use ...
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Understanding the Communication Protocol of Apple HomeKey
I am currently analyzing the communication protocol of HomeKey. Here are two traces between the lock (reader) and the device (card).
First set:
...
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who creates the passkey (and how many will be created)? [closed]
Passkey is nice. The math is nice. The tech is nice. https://security.googleblog.com/2023/05/so-long-passwords-thanks-for-all-phish.html
What I still dont see after sooo many hours: what software ...
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How many bits should change in a password salt?
In https://crypto.stackexchange.com/a/27828/79037, it's indicated that one can "save space" by using something globally-unique, like an application-wide "pepper", together with ...
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Parameters needed for Chaum-Pedersen Protocol
I've came across a Stackexchange question about the Chaum-Pedersen Protocol which is based on the generalised schnorr protocol. As I understand it, it uses discrete logs and cyclic groups of prime ...
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Is it undesirable for authentication to require decrypting a ciphertext?
A couple years ago, I devised some primitives for block ciphers and block cipher modes of operation; I was partly inspired by CAESAR. What these designs all had in common is that the encryption/...
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Man-in-the-Middle attack on challenge-response authentication protocols
Say $B$ is a server and $A$ is a client who wants to login to the server, by proving herself to $B$. In challenge-response authentication protocols, $B$ sends challenge to $A$ and $A$ replies with ...
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Providing tokens for anonymous survey
I want to conduct an anonymous Internet survey (e.g. “What’s your favorite fruit?” with a multiple choice answer) among a given set of people. Double answers by the same participant are not allowed.
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Authenticated Key Exchange of Kyber.AKE
I have some questions about the setting of the one-way authenticated key exchange of Kyber.AKE as defined in section 5 of the paper.
How does $P_2$ authenticate itself to $P_1$? It is not obvious to ...
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Does the order of validations and MAC with clear text matter?
I have a request in which I get a series of data in clear (nothing encrypted) and a MAC / authentication tag.
The question is whether the MAC should be validated first or if the fields are filled in ...
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Securely sign URL using a 50 characters long key
I need to sign a URL to make sure the URL cannot be tampered or forged.
The client has limited capabilities and I cannot use a key which is more than 50 characters long.
Generally I use RSA to ...
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Secure two-factor authentication app for iOS
I'm working on an open source iOS-native (both UX- and implementation-wise) 2FA app. Two of primary goals for the project are ensuring security and simple backups. Addressing these two areas is the ...
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Does having more than one HMAC provide more information to the attacker?
Suppose $N$ many messages has been sent from $A$ to $B$ in this format:
$\operatorname{HMAC}(K, C(i)) \mathbin\| C(i)$.
Where
$C(i)$ is some cipher-text encrypted with some secure algorithm using ...
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How to authenticate multiple IOT devices having unique certificates (ECDSA)?
I'm relatively new to the field of security.
I'm working on an IoT system with WiFi-connected nodes (Bio-sensing devices) communicating with a server for centralized monitoring.
I need to authenticate ...
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How do non-"resident" keys work in WebAuthn?
If we look at the WebAuthn specification, then, during the "registration" ceremony, the authenticator generates a new key-pair and a unique user-id. Then the public-key and the unique user-...
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Why does FIDO2/WebAuthn really need to generate a separate key-pair for each site?
I understand that FIDO2/WebAuthn generates a separate key-pair for each web-site (domain), and only allows a specific key-pair to be used for authentication on the same web-site (domain) who ...
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Security of using key size larger than the message digest size in HMAC, with one time pads
I would like to know the security of using key size that is larger than the message digest (output) of a HMAC in one time pad encryption.
One time pads for the message and the key of HMAC are ...
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I understand the authentication procedure, but are replay attacks possible in these scenarios?
Would a replay attack be possible in any of these scenarios? My understanding is that in only images 3 & 4 it is possible.
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Disk encryption and advanced format
As far as I understand, the biggest problem of requesting authentication in disk encryption is that the plaintext and ciphertext are not having the same size -because of tag-. The XTS mode is already ...
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Is it safe to use ECDH shared secret as a simple authentication cookie?
The protocol would look like this:
User creates account and provides username, static public key
User logs in by sending username
Server responds by sending an ephemeral public key
For the duration ...
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UF-naCMA not implies UF-CMA
I am trying to show that UF-naCMA doesn't imply UF-CMA. UF-naCMA is actually defined as UF-CMA but the adversary should send $q \in poly$ messages $m_i$ chosen non-adaptively (i.e. all at the same ...
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Why is ZKP authentication not used in practice?
I have been reading about Zero Knowledge Proof (ZKP) protocols for a while now. Among the applications I have seen the most is authentication (https://ethereum.org/en/zero-knowledge-proofs/#...
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Data Origin Authentication vs Non Repudiation?
I'm looking into how authenticated encryption primitives work and was wondering if non-repudiation is provided with these. Investigating further into them led to the answer being that data origin ...
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Does anonymous authentication based on ZKP have better unlinkability?
I am confused about whether/how ZKP based entity/message authentication scheme can achieve identity privacy, especially unlinkability. The security properties I'm looking for in the scheme is ...
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What drivers are causing an increase in authenticated encryption modes?
So I'm currently working through this cryptography question and so far I have the answer of an increase of hackers due to increase in computational power. But apart from that I don't know what else. ...
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How does TLS 1.3 provide authentication without using the public key to verify that the server has a private key?
In the TLS 1.2 handshake, after checking the certificate, the public key from the certificate was used to encrypt the data to create a symmetric encryption key, hence the authentication took place on ...
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Authenticate people online with simple public / private key scheme or similar
How can I ensure that person X on website A is the same person who contacts me?
Here is my use case.
On website A I post message asking username X to contact me. Someone send me an email - how do I ...
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Base64 or hex to attach auth tokens to URL?
I just came across this question, but it does not really answer my main concern that I have regarding password tokens.
To authenticate a client who is not logged in; I generate two random tokens and ...
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How LastPass decrypts database on web browser?
According to video from Dr. Pound, password managers (LastPass in particular) holds encrypted image of your data on their servers and then with master password you authenticate to get encrypted image ...
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Why is the following not a ZKP for discrete log?
Before looking at the textbook ZKP for discrete log, I tried to construct one myself. This turned out quite different to the textbook one, and I've been wondering what might be wrong with it? (I was ...
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How can a root CA be kept offline and function
Based on many suggestions I have seen around, this, that.etc. Best practice says to keep the root CA offline for very understandable reasons.
But how can it be truly offline? Doesn't the root ca have ...
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Aes-Gcm how to perform decryption authentication without plaintext output in C#
I'm mainly trying to verify large file chunks which are encrypted each alone with a different key/salt/nonce for each chunk then appended to the whole file in the end to form 1 file.
One thing I ...
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Hash Function Vs Signature Vs MAC?
I read: What are the differences between a digital signature, a MAC and a hash?
and Found this amazing answer: https://crypto.stackexchange.com/a/5647
But one question remains:
I know that for huge ...
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How does AES GCM encryption work
Previously, I used AES CBC 256 with 256 bit key and 128 bit IV.
However it seems slow so I decide to switch to AES GCM 256 bit key, 96 bit IV which has some parts I don't understand such as:
Auth tag:...
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Comparison Hash, MAC, Signatures, Certificates
I saw a table comparing Hash/Mac/Signatures in this post.
I was wondering if I can integrate digital certificates into it like this:
Hash
MAC
Signature
Certificate + Signature
Integrity
Yes
Yes
Yes
...
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I don't undertand the meaning of 'Authenticity' property
Considering an HMAC algorithm: it shall guarantee integrity and authenticity. I don't understand what authenticity means: that signature could be generated by anyone having the shared secret key (non ...
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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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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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