All Questions
Tagged with protocol-analysis encryption
24 questions
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45
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Order of Enigma's rotors does not increase total number of keys
I have a question about “order of rotors”. I read about Enigma but I do not understand this point. If the machine has 3 rotors, for example 1_2_3, so it has 26×26×26 total keys. If we change the ...
- 27
3
votes
1
answer
1k
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How does SMB authentication work?
When I learned about the inner workings of the TLS protocol and what exactly it protects a connection against, I was surprised to learn that even asymmetric encryption can be defeated by a MITM attack ...
- 161
2
votes
1
answer
262
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Confirming understanding of security protocol modelled in Scyther
In university, I'm currently learning how to use Scyther to model security protocols. Currently I am trying to understand what is happening in an example protocol given to me which is:
...
- 77
14
votes
1
answer
3k
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What is universal composability guaranteeing, specifically? Where does it apply, and where does it not?
I don't have a proper computer science education, so bear with my misunderstandings.
UC is supposed to "guarantee strong security properties". From what I stand, if you have some secure ...
- 352
3
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1
answer
541
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Does using Noise asynchronously weaken its security properties?
Can Noise be used asynchronously without weakening its security properties?
Specifically, there are two users, A and B, who communicate asynchronously by leaving messages for each other on an ...
- 105
-1
votes
1
answer
88
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Which encryption mode is best for transport of random values?
I was wondering which block encryption mode or modes will be most appropriate for transport of random values of one-block length. Block length could be of size 256 bytes and transport is from person ...
- 111
2
votes
1
answer
73
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Are the following asymmetric encryption schemes equivalent?
Consider the scenario where you want a machine to be able to send daily encrypted backups to a storage server.
You'd prefer to not use simply a symmetric key for encryption, because if the machine ...
- 4,790
0
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1
answer
99
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Is function Deterministic or Probabilistic in the malicious security definition?
As you see, according to the attached definitions from "Efficient Secure Two-Party Protocols", the definition of the security in the semi-honest world has two cases for $f=(f_1,f_2)$.(deterministic ...
0
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1
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493
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Basic encrypted custom protocol
I've been suggested to ask here instead of stackoverflow, so here I am.
I'd like to encrypt the data of my application that uses a custom protocol I've created. I know about TLS and other protocols ...
- 13
59
votes
2
answers
12k
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Is the software that uses PGP broken, or is it PGP itself?
PGP is all over the news (even on TV) and there seems to be a lot of confusion about it.
For the time being, people face articles like Attention PGP users: new vulnerabilities require you to take ...
- 18.1k
16
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2k
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Has Telegram security been significantly improved with MTProto 2.0?
Telegram messenger's original encryption scheme, MTProto 1.0, has been shunned by most cryptographers for a number of reasons, like being vulnerable to IND-CCA attack; being unorthodox in general, ...
- 161
1
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1k
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Is the crypto riot.im claims to use safe? [closed]
My friends want to communicate with me using “about.riot.im”, I tried to research them and the protocols they claim to use and I only found their own websites promoting it, so the whole thing seems ...
- 119
-5
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1
answer
116
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Is a symmetric cryptographic code secure if only the sender and recipient know the method used to encrypt? [closed]
I recently designed an encoding method that I'm fairly sure is unique. Is it universally secure, provided that anyone intercepting the message doesn't know anything about how it was encrypted? Could ...
7
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0
answers
363
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Security proof in (Ciphertext-Policy) Attribute-Based Encryption
I am having hard time understanding the security proof in Attribute-Based Encryption, especially in Ciphertext-Policy Attribute-Based Encryption.
To do reduction in CP-ABE scheme, how do I check that ...
- 71
6
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1
answer
2k
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Security of Fernet Construction (wrt non self delimiting tokens and HMAC short key size)
Fernet is a described as a "high level symmetric encryption recipe" (source) that seems to be the default high level encryption scheme in the cryptography python ...
- 4,062
0
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0
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142
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Permuted Hash Table
Suppose we have a hash table, $HT$, consisting of $100$ bins.The hash table uses a hash function $H$ that is public.
We all know that given value $a$ we can compute the address in the hash by $H(a)=j$...
- 1,583
0
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0
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59
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When we use permutation and random long sting to hide a message
This question is modified version of this:
Can we use merely permutation to hide a message?
I have an English name $m=m_1 || m_2 ||..||m_{30}$.
I pick a random string $d=d_1 ||..||d_{70}$
I mix ...
- 1,583
1
vote
0
answers
40
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Security issues with self encryption? [duplicate]
I'm thinking about the scenario of using a set of (potentially untrusted) hosts to store (potentially private) files. Think something like distributed backup where you contribute some disk space and ...
- 111
8
votes
5
answers
3k
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Does frequent key change weaken encryption?
Following scenario:
We are using OTR for communication between Alice and Bob which means after each successfull message exchange a re-keying happens for both parties leading to new AES-keys for the ...
- 131
0
votes
1
answer
679
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Comparing messages given only the ciphertext
Under RSA protocol I was wondering how a message sent could be verified
under the following scenario
Alice has a private (encryption key) and public key (decryption key)
If Bob sends Alice cipher-...
- 101
3
votes
2
answers
106
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Re-sending captured encrypted data
Let’s assume Bob is some algorithmic stock trading machine. Bob takes commands from Alice, who sends messages to Bob.
For example: Alice could be sending a message to Bob to stop trading. But if ...
user28093
2
votes
1
answer
149
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To prove $r \cdot f_1 +f_2 \cdot (s+1)$ is secure
We define the polynomials $r, f_1,f_2,s \in R[x]$. Where $r$ is a random degree 1 polynomial and $s$ is a random polynomial such that: $degree(s)=degree(f_1)=degree(f_2)$, let $R$ be $\mathbb{Z}_p$ ...
- 1,583
4
votes
2
answers
877
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Spoofing protocol nonce
Amy and Betty have a shared key $k$, and the protocol below is to provide a mutual authentication for both Betty and Amy.
A sends B : $n_a$
B sends A : $n_b \;\|\; E(k, n_a)$
A sends B : $E(k, n_b)$
...
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7
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1
answer
647
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Can two people with different one time pads securely exchange a message like this?
Alice has a message, generates a one time pad, encrypts her message and sends it to Bob. Bob generates his own one time pad, encrypts the message again, and sends it back to Alice. Alice then decrypts ...
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