All Questions
Tagged with symmetric protocol-design
24
questions
1
vote
0
answers
41
views
In Kerberos, is the "Authentication Server" the only "Trusted Third Party"? Or is "Ticket Granting Server" also a "Trusted Third Party"? [closed]
I know that AS (Authentication Server) is a TTP (Trusted Third Party) because it generates keys for two entities (for the client and the TGS).
But what about TGS (Ticket Granting Server)? It also ...
- 51
0
votes
2
answers
692
views
Designing a simple challenge-response symmetric mutual authentication protocol
I am designing a protocol that 2 devices will use to mutually authenticate over an unreliable, unsecure channel. The system must be fast and low-power, so symmetric cryptography is a requirement. I ...
- 101
0
votes
1
answer
524
views
What's the utility of the last two messages of Needham Schroeder Symmetric key protocol
The protocol works like this
But I can't understand what's the utility of message 4 and 5, what do they protect from?
They do not protect from replay attack if Ks gets compromised because B won't be ...
2
votes
1
answer
915
views
Key derivation for AES-GCM using HKDF?
I have a system comprising N >1000 nodes. At each node I would like to use HKDF to derive a unique 256-bit key, Kn (for the nth node), from a pre-shared master key, K0, and a locally-generated random ...
- 21
2
votes
1
answer
349
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Detect MITM with hashed session-key — Is my protocol secure?
I have the following setup:
An app ("client") wants to communicate securely with a device I created ("server").
The client has the public key of the server (and a hashed password) preinstalled.
I use ...
- 23
4
votes
3
answers
618
views
Role of session identifier in Otway-Rees protocol
According to Wikipedia, Otway-Ress protocol is as follow:
The protocol can be specified as follows in security protocol notation, where Alice is authenticating herself to Bob using a server $S$ ($M$...
- 41
0
votes
2
answers
140
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Signing an exchanged symmetric key that is asymmetrically encrypted
Consider the following implementation:
Bob wants to communicate long-term with his team over an unsecured channel. Bob and all members of the team generate individual public/private keypairs (ex. ...
- 591
3
votes
3
answers
256
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DIY message level security?
This might be in danger of being too elementary a question for this community but I'm hoping for expert help:
Assuming that TLS is not enough to protect messages transmitted between a client and a ...
- 139
4
votes
1
answer
2k
views
end-to-end encrypted chat app with symmetric + public key encryption, TLS and cert pinning
A big drawback of end-to-end encrypted messaging services is that, as soon as you lose your device, you lose all your messages. Your private key is gone after all. I was wondering though, wouldn't it ...
- 43
6
votes
1
answer
197
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How to use a stream cipher to sign a message?
Are there known constructions which allow to sign a message M
(let's say it will be sent as clear text) using a stream cipher C
and a symmetric secret key K?
So, we have M, C, K and we want to send M|...
- 385
9
votes
1
answer
2k
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What is the original SKID3 protocol?
While searching for a mutual authentication protocol I often stumbled upon SKID3. However I encountered different variations of it.
The basic structure is the following:
(1) $A \rightarrow B: r_A$
(...
- 161
1
vote
0
answers
84
views
Encryption with a known plaintext
I'm building an application where users can be a part of groups, and can obtain and distribute URLs from the group page that allow anyone who clicks on them to join said group. Groups should not ...
- 11
1
vote
1
answer
255
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Key management protocol for end-to-end security on Advanced Metering Infrastructure
I am currently working on a research on end-to-end security implementation for Advanced Metering Infrastructure (AMI). Pardon me if I a bit off topic or not asking the right question as I am ...
- 11
1
vote
1
answer
218
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Basic question about design of program with data encryption
I need to store encrypted files on a hard disk. The actual code side is not important for me now (I plan to use C# and AES-GCM encryption from Bouncy Castle library, please tell me if you think that's ...
1
vote
2
answers
1k
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Are SSL/TLS used for maintaining data confidentiality?
In SSL/TLS, we use symmetric and asymmetric keys to encrypt the data. Does that mean that the keys are used to encrypt the data (preserve the integrity) or provide a secure channel for the data to be ...
- 217