Tagged Questions

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
91 views

Is there need for message authentication if a public key is transmitted and then used to encrypt a symmetric key?

First I'd like to note that I'm really a beginner at cryptography, and while this interests me and while I have researched it in the past few months, there is still a lot of things that simply aren't ...
3
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2answers
73 views

Group membership with unique anonymous claims

Is it possible to accomplish the following scheme? There is a Server (S) and many clients. Each client enrolls with S, exposing its real identity; S saves the real identity information in its ...
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1answer
181 views

What is the best way to share a shared secret key over HTTPS to be used for HMAC authentication?

I am writing an application in Java that will be using SHA-1 HMAC message authentication. From what I understand, a connection over HTTPS is considered secure enough to share a secret key in plain ...
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0answers
83 views

Is MITM possible after key exchange phase done successfully in RSA?

Is MITM attack theoretically possible after public/private key pair exchange is done successfully. Say Alice and Bob have genuine public keys of each other. Is MITM possible further during ...
3
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1answer
314 views

Any use for now-defunct Mt Gox Yubikey?

As everyone is now aware, Mt Gox has declared bankruptcy. As what appears to be the very last thing they did, Mt Gox accepted my $35 and fulfilled my special Mt Gox Yubikey. Having just arrived in the ...
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1answer
211 views

Check the validity of a rsa key pair with only the public key? [duplicate]

I am currently developing a messaging application that uses rsa end to end encryption. The client generates permanent rsa keys, and sends the public key to my server for account management. As it ...
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2answers
423 views

Digital Signature using symmetric key cryptography

Generally digital signature is a public key cryptography concept.But it needs high overhead. So is there any publication or link available where 'digital signature using symmetric key' has been ...
3
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1answer
972 views

Diffie-Hellman Key Exchange with Authentication: Man-in-the-Middle query

I have been reading up on MiTM attacks, and the prevention of them using public key certificates. Recently I learnt about Diffie-Hellman Key Exchange with Authentication, and how it uses signed ...
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1answer
64 views

OTP sequence uniqueness

Is it possible to use Time-based One Time Password (TOTP) algorithms to generate tokens from multiple channels (where a channel is defined as a "user" using a certain shared key $K_c$ for channel ...
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0answers
104 views

Safe and computationally efficient way to verify a curve25519 identity?

A client identifies itself as a curve25519 public key. The server wants to verify the client owns the associated private key. Is there a safe and computationally efficient way of doing so? Which ...
2
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3answers
223 views

How can we sign a contract digitally between two parties?

I'm trying to sign a contract with another party, without using handwritten signatures. I've just read through Applied Cryptography, but there doesn't seem to be a protocol that can solve this ...
0
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1answer
189 views

Unique, anonymous online authentication

Is there a way to authenticate users online without knowing their real identity yet preventing them from registering twice? If not, what is the least amount of information you would need? If it helps, ...
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2answers
91 views

Why is this authentication procedure using Rabin crypto not useful?

A friend asked me the following, pointing out that the method is not very useful (my problem is I do not see why it is not good): Consider a person A which chooses $n$ as the public key for the ...
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1answer
117 views

Encrypting a TCP connection between two unknown nodes

I'm writing an application for controlling computers from a client. I'd very much like it if the connection is secure and only authenticated clients are allowed access. The workflow will be ...
3
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2answers
180 views

Why have Nonce and why encrypt everything in step 2 for Needham-Schroeder?

Here is the protocol outline I am looking at (source: Foundations of Computer Security, Lecture 60: The Needham-Schroeder Protocol) $$ \begin{array}{ccl} 1.& A \to S \colon& A,B,N_a \\ ...
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2answers
484 views

Can a salt for a password hash be public?

For my understanding salts in password hashes are used to prevent the precompuation of plaintext$\to$hashvalues (rainbow tables). I know from different threads, it is not necessary to keep the salt ...
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0answers
42 views

How to select parameters based on some condition

I am implementing a protocol for authentication where parameters need to be selected with $gcd(\mu,\phi)=1$ where $\phi=(p−1)(q−1)$. What is the best way to select the parameters while implementing
3
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1answer
142 views

How to attack this authentication protocol from “Cryptography: An introduction”

Consider the following protocol (from the book "Cryptography: An introduction", by Nigel Smart): ...
5
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1answer
249 views

What is 'Carry-forward verification' defense against MITM?

Wikipedia article on Man-in-the-middle attack mentions, in the list of defenses against it, some method called "Carry-forward verification", but it does not explain it. I am curious about different ...
2
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1answer
97 views

Proof of shared secret through key derivation

Alice gives a random key $K$ (e.g. 32 bytes long) to Bob through a secure channel. Bob want to prove to Alice through an unsecured channel that he knows the key. Is it secure for Bob to send ...
2
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1answer
170 views

Off-the-record communication

Is my protocol correct? For fun, I tried to design a protocol that would allow off-the-record communication. I'm not sure it works, I have a feeling there might be a problem with it that I'm not ...
10
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1answer
209 views

Shadowed identity in cryptography

I was trying to implement zero knowledge protocol for authentication based on the paper "A Practical Zero-Knowledge Protocol Fitted to Security Microprocessor Minimizing Both Transmission and Memory". ...
2
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1answer
100 views

With Encrypt-then-MAC, and flexible protocols, do I need to authenticate the authentication?

Sorry, the question is not easy to state (or wasn't for me, anyhow). So I'm writing a very flexible format for security. It allows for full choice of cipher, key size, and so on, along with key ...
2
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2answers
101 views

Is this algorithm demonstrating “proof of work”

Is this algorithm demonstrating proof of work? This is a algorithm where a "token" is combined with a time stamp and then a cryptographic hash is generated from the combination, next the objective is ...
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3answers
502 views

How to perform authentication without central server in P2P?

How can one be sure that the man who you're talking with is the one who you think he is? i.e. How can one perform authentication in P2P network without a central trust server or Certificate Authority? ...
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3answers
219 views

Is the following authentication protocol insecure?

I am a student taking cryptography this semester. I was just wondering why can't we use this simple protocol? Alice → Open Connection → Bob Alice ← Cert$_b$ ← Bob Alice → {K$_{AB}$}$_{Bob}$ → Bob ...
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1answer
54 views

What vulnerabilities would open up if PGP authentication didn't have integrity checking?

It is my understanding that PGP has both an integrity check and an authentication check. What vulnerabilities would open up if it didn't have that integrity check? It seems like the authentication ...
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1answer
64 views

Authentication mechanism for low memory, low computing power device

I am looking for an authentication mechanism that works best with low memory, low computing power devices. I came across a paper "A Practical Zero-Knowledge Protocol Fitted to Security Microprocessor ...
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1answer
98 views

A replay attack question

Which of the following protocols is susceptible to replay attack :- 1) A -----> B username, password 2) A -----> B username, h(timestamp,password) 3) A -----> B username timestamp, ...
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0answers
38 views

Why doesn't this authentication protocol work? [duplicate]

I am a student taking a cryptography course so forgive me if this comes off as a silly question. This is an assignment question: Alice ------R--------> Bob Alice <-----[R]B------ Bob Alice ...
3
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2answers
149 views

Why doesn't this dummy mutual authentication protocol provide mutual authentication?

I am a student taking a cryptography course so forgive me if this comes off as a silly question. This is an assignment question: $Alice \rightarrow R \rightarrow Bob$ $Alice \leftarrow [R]B ...
4
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3answers
185 views

Why can an RSA signature be authenticated ONLY with the signer's public key?

I'm an undergraduate Math student currently taking a cryptology course. I have a question about the RSA signature authentication mechanism. An RSA signature can be authenticated with the public key ...
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2answers
249 views

How does Google's “authenticator number generator” work?

I have two-factor authentication enabled on my Google account, and I have this app on my phone which generates a number I have to type when I'm logging in to Google-Mail. But I don't understand how ...
2
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1answer
199 views

Is this new server API authentication protocol secure?

I need a secure protocol to authenticate client side users with my server which has an API. I am devising something more secure particularly to resist active MITM attacks where an attacker may modify ...
2
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1answer
114 views

Authentication of machine before installation (to stop piracy) [closed]

I have a web-software project which needs a bit of protection in form of authencitation… This web based software runs on an intranet. There is no access to the internet from these terminal machines. ...
1
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1answer
69 views

Why send a challenge with CHAP?

I have been reading about the Challenge-Handshake authentication Protocol (aka CHAP). Why send a challenge to the user and ask them to hash that challenge with the symmetric key and send that hash ...
0
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1answer
87 views

Biometric authentication [closed]

I see in some “Authentication schemes with biometric” papers that those authors wrote a phase as password and biometric update phase. My question is that why we may needs biometric update phase? Is ...
3
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1answer
146 views

What does this Authentication protocol achieve and what information is shared?

I'm having trouble with the following question from my class: "What is the purpose of the protocol, and how does it achieve this purpose and what shared information does A and B end up after ...
3
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1answer
458 views

OpenPGP/X.509 bridge: how to verify public key?

I'd like to use OpenPGP authentication over TLS, but lack of implementations made me use a temporary solution: an OpenPGP/X.509 bridge certificate. The approach is very similar to the approach used ...
2
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1answer
112 views

Genuine encryption from only one source?

Is there any technique so that if I encrypt data, the ciphertext would be genuine and if someone else tries to encrypt the same data the ciphertext could be determined as fake or just invalid? I want ...
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1answer
377 views

Schnorr Identification Scheme under active adversary

According to the paper “GQ and Schnorr Identification Schemes: Proofs of Security against Impersonation under Active and Concurrent Attacks” by Mihir Bellare and Adriana Palacio, the Schnorr ...
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2answers
107 views

Self authenticating tamper resistant first meetings

I'm not sure what the precise words I am looking for are so I apologize if there is a better way to phrase this. What I am thinking of is ways to transfer an identity in a way that it is tamper ...
2
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2answers
351 views

Please punch holes in this authentication scheme

Folks, I am undertaking a crypto course in Uni. Our professor asked us to try and design some authentication schemes which are resistant to active attacks. This was just a in class exercise to get us ...
2
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1answer
229 views

Verifying Self-signed SSL Client Certificates

I have a service and I want to authenticate my clients using SSL client certificates. Now I want the key exchange process to be as simple as possible, kind of like SSH: You generate a keypair and ...
3
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1answer
114 views

What security differences are there between E(p',“well-known-plaintext”) vs. hash(p') where p'=KDF(p)

I am using a KDF to derive a key, p' from a password p. I would like to know if the password is correct before using the derived ...
2
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0answers
139 views

Integer factorization based password authentication

After looking at this security issue at DjangoProject, I started to think in a password-based authentication that places the burden of PBKDF2 (or whatever is the hashing function) on the client. So I ...
2
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2answers
286 views

Storing Credentials for a Third Party

(Originally posted to SOF, but I got no answers) I am designing a small application for use inside my company. My application needs to connect to a third party website on behalf of my application ...
5
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1answer
111 views

Authentication protocols for authenticating devices to a server

The requirement is to authenticate 1000s of devices to a server when the devices try to contact the server. The problem I face is that all authentication protocols require some kind of shared secret ...
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2answers
194 views

What security flaw exists in MAC authentication scenario?

What security flaw exists (if any) in the solution of this non-encrypted authentication scenario? An unencrypted message passes one-way from computer A to B. Its transmission is viewable by the ...
2
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1answer
113 views

Can an encrypted nonce be used for authentication?

Would a scheme like the following work to allow authentication of a sender: A nonce is appended to data, and the result is encrypted. The encrypted pack is sent to the other party. The sender then ...