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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Why is authentication needed between Alice and Ticket Granting Server in Kerberos Protocol

Being the messages of the protocol: With KAS = Kerberos Authentication Server, TGS = Ticket Granting Server, B is a service and T1 T2 T3 T4 are timestamps. I was wondering why is the "...
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Why does a nonce prevent a replay attack?

I have a question about a cryptographic nonce. I understand the use of a nonce, however there is one particular part that I don't understand. Please consider the picture below. I don't really ...
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Crypto AES for authentication

Is it secure to use authentication strategy like this: store key in database - crypto.randomBytes(32) store IV and encrypted data in user cookies - ...
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If we have chunk encryption for AES-Rijndael-CBC, should we hash Authenticate/tag each single chunk with a hash vs whole file?

was frustrated by which one to pick and my brain could not guess which one is better Authenticate the whole file as one with a hash vs authenticating each ciphered text. So very quickly: i have super ...
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Unilateral Authentication hash type for verification

The scenario: Alice wants to exchange information with Bob on an encrypted channel proxying through Pete (Pete can't read the info sent between Alice and Bob), but doesn't want Bob to know who she is, ...
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Is the first Nonce exchange between Alice and Bob in Needham-Schroder key exchange protocol redundant?

For the Needham-Schroder protocol, assuming Alice and Bob are both able to guarantee each other's public keys (e.g. through a Certificate authority), the protocol is 1) A sends to B: $E_{publicB} [...
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TLS client authentication from static client image

I'm trying to implement mutual authentication for a TLS connection between a server (ONOS OpenFlow controller) and multiple clients (OpenFlow switches). I'm restricted in that I must create a single ...
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How is Diffle Hellman with RSA immune to man in the middle?

Alice and Bob want to exchange keys, Alice sends his half (the public key of the ephemeral key pair) signed with his private key and makes the public key available. Eve is bridging the connection so ...
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CHAP vs EAP-MD5

I started studying EAP authentication framework and I don't understand why was the EAP-MD5 developed. Why not just use the CHAP protocol ? To me they seem the same. Can you explain to me ?
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Counters in HOTP

In the HOTP (HMAC-based One-time Password algorithm ) algorithm the client and the server can have different counter values. Es. if an attacker tries to crack the password with no success. How HOPT ...
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Non Repudiation - Message Authentications methods

According to a definition given by my professor: Message authentication methods verify that the message is from the right sender, however they don't guarantee non-repudiation. To me this sounds ...
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Where are labels of a Labeled data used in homomorphic message authenticator stored?

In a fully homomorphic message authenticator, Alice can authenticate some large data $D$ using her secret key $s$k. She chooses a label $\tau$ for it, and the authentication algorithm authenticates ...
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Key exchange and authentication using libhydrogen

I have been able to exchange session keys on two devices using Libhydrogen's Key exchange using the N variant method. I also want to authenticate both devices to have some protection against the Man ...
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Is there a reason to use multiple hashing algorithms in a single system?

I came across an authentication system Here that uses multiple hashing algorithms to hash data in different stages of the authentication. My question is what's the rationale behind this? If a hashing ...
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Lightweight provably secure design [closed]

Is it possible to device lightweight (i.e. without asymmetric crypto and PKI; and without third party Trent) provably secure (in the exact security sense) scheme? Were there any attempts? Is it ...
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Existence of MAC implies existence of OWF

I'm having trouble understanding how the existence of a MAC implies the existence of an OWF. If the MAC protocol is $(\operatorname{Gen}, \operatorname{MAC}, \operatorname{Ver})$ such that for any ...
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Question about PKI-based non-deniable authentication by Canetti et al

In Universally Composable Authentication and Key-Exchange with Global PKI, Canetti et al. proposed a non-deniable authentication functionality as well as a protocol that GUC-emulates it. My question ...
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Digital signature forging on a server, after entity authentication [duplicate]

Lets assume there is a guy called Ben, he contacts some server for a ticket number and the server returns a random number to him. Ben then signs that number and sends it back to the server, which ...
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Is using HMAC signature as a long-term password secure?

I'm considering implementing an authentication service without storing users' passwords/hash. I want to use a key derivation function with a corresponding username...
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Unconditionally secure message authentication, how does it work? [duplicate]

The definition of an unconditionally secure cryptosystem is that it cannot be broken even with infinitely computational resources and time. The one-time pad (OTP) is an example of an unconditionally ...
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How does Gilbert, MacWilliams, and Sloane's solution to “perfect integrity” work?

Gilbert, MacWilliams, and Sloane defined a solution to "perfect integrity" in Codes Which Detect Deception, unconditionally secure message authentication, not vulnerable to any cryptanalysis on its ...
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Why do one-time pads not provide message authentication?

It is often said that one-time pads do not provide message authentication. But, if you and I have a one-time symmetric key, and I send you a message, and it is not complete gibberish, is that itself ...
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HMAC based Key exchange

Alice and Bob need to share public keys to sign/verify ephemeral keys. They have a secret key $K$. Alice generates a 32 bytes random number $A$, computes $\operatorname{HMAC-SHA256}(K, M||A)$ and ...
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Is it necessary to have a certificate when we use TLS

When we say a communication is secured by the latest version of TLS, can we say that Man-in-the-Middle attack is not possible? Do not consider the situations that we can down grade the communication ...
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How are AEAD, GCM, CBC, Poly1305, EtM, MtE and E&M related?

I am using OpenSSL 1.1.1 to implement a TLS 1.3 communication module so I tried to learn how data integrity and authentication is ensured. I read a lot about AEAD, GCM, CBC, Poly1305, EtM, MtE and E&...
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How secure are public hashed passwords (with a salt)?

I'm working on a blockchain-based distributed application which stores Client information. I'm thinking of alternate ways to authenticate ...
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What is used as a KEY and MESSAGE when using HMAC within a PBKDF2? [duplicate]

I was studying WPA2 and it's security when I came across this problem. I know that WPA2 uses PBKDF2 to generate a Pairwise Master Key. It does something like this; ...
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Is there a human readable easier version to represent PGP Private keys?

I'm working on a distributed application, and we need a way to authorize clients. Every client has a PGP keypair associated with them, and we require them to enter their private key (which is not ...
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Authenticating without sending password to the server, and store data encrypted with password derived key on server

I am trying to think of a scheme that would allow a user to authenticate to a server, whithout sending the password to the server, and to also derive a symetric key on the client (that also never gets ...
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What security is provided by a certificate? [closed]

I've been working on the topic of certificates for a little while, and here is what I understand: A certificate is basically a public key + some data about the owner of the certificate + a signature ...
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How many AES 128-bit keys does a MIFARE PLUS tag have?

I know that the question is a bit silly but I dont know how many keys can a MIFARE PLUS tag store in it. Provided that I have a MIFARE PLUS S tag with 4k memory room and the key length is 128 bit, ...
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Authentication and encryption using a simplex communication channel

Is it possible to authenticate a client with encryption on a simplex communication channel without the use of authoritative root certs?
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Privacy and warrants to obtain information

How could a site issue a `warrant'*, a document which: 1) Others can verify was issued from that site 2) Contains a date stamp, a named site and instructions which can be presented to a third site by ...
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Pen and Paper Authentication

What is the best way to prove that you wrote the encrypted message on a piece of paper? As most of us know, many conspirators have died because of false message implants, Mary Queen of Scots, for ...
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Understanding hybrid cryptography's concepts: signing and CA

After learning about symmetric encryption, public-key encryption, one-way hash, digital signature and digital certificate, I was tasked to think of an imaginary hybrid cryptosystem. I was thinking ...
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Why does 3-way authentication need the 3rd nonce to be stored?

In the following 3-way authentication protocol: A -> B: $N_a$ || B || Signature_KprivA B -> A: $N_a+1$ || $N_b$ || A || Signature_KprivB A -> B: $N_b+1$ || Signature_KprivA ($N_a$ and $N_b$ are ...
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Hashing a hash for authentication

I currently use Argon2 to derive a key (I will use a salt which I will save in a file as plaintext for when I later need to derive a key again) from a given password which I will use to encrypt a file ...
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Entity authentication protocol by encryption

I'm not a cryptography expert, so excuse me if the question seems very trivial. I need to know if this protocol is secure against a MiTM attacks and ensure a safe entity authentication method. We ...
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Where shall we use an authenticated encryption mode?

I learned from Wikipedia that authenticated encryption modes include OCB, CCM, EAX, GCM, and so on. Does this mean that when we want to use authenticated encryption we shall use these modes? But these ...
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Digital Signature Password verification

I currently have this TOFU protocol: First connection: Client generates salt and inputs a password Client saves salt Client hashes password with argon2 and salt Client generates Ed25519 keys Client ...
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How does the offline authentication work?

In these slides, offline and online PUF-based authentication protocols are explained in minute 16:30 and 17:30, respectively. I understand the way the online protocol works. Basically, the server ...
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What is the security concept in printer cartridge?

Based on this datasheet or this patent, one of the usage of PUF is printer cartridge identification and authentication. I was wondering why printer cartridge needs identification and authentication. ...
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How can I get select messages ciphers for salsa20poly1305 for unit tests?

In order to avoid memory errors, I always write safe C++ wrappers with strong type-safety for any C encryption library I use. To test my wrapper of ...
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How can I follow the validation and verification recommendations of the NaCl (sodium) secretbox library?

I was advised to use crypto_secretbox_xsalsa20poly1305 due to its simplicity and because it's safe against timing attacks. I'm reading the secretbox tutorial, and ...
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How to Understand Authenticated Key Exchange?

I am reading some articles about key exchange. I know classic key exchange, such as Diffie-Hellman key exchange. This type of algorithm is vulnerable to man-in-the-middle attack. However, when using a ...
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How to implement correctly a “secure” authentication protocol? [closed]

Due to my lack of knowledge in this matter I am facing some problems to identify which features are sign of a bad implementation of a symmetric authorization application. As I am concerned the system ...
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Why CBC-MAC encrypts at each step

Considering CBC-MAC as: $\qquad H_0 = IV = 0$ $\qquad H_i = E_k(P_i \oplus H_{i-1})$ $\qquad MAC = H_n$ What are the properties that makes this "safer" (less ...
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How simple hash provide message authentication?

This structure provides message authentication. My question is if someone finds the key he can simply change the message and compute new hash according new message and send it to the receiver. If so, ...
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Timestamps, sequence numbers, and nonces for replay attack

What are the best practices or standardized methods to prevent replay attacks in a simple server client setup (preferably where the server is stateless) ? When should timestamps, sequence numbers, ...
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AES, CMAC and “3 pass authentication protocol” Explained

I am struggling a bit to understand how authentication systems are properly used in NFC tag environments so I'm posting this thread to clarify some concepts.(In advance, this is not my field, so ...