0
votes
1answer
33 views

Possibility for same Private Key Generation in identity-based encryption

In private key generation of IBE scheme, private key is generated as follows: $SK_{ID}=s.H(ID)$ Suppose two servers use the same curve domain parameters. If PKG on server A generates private key ...
3
votes
1answer
64 views

Deriving AES key and HMAC key from shorter master key

I am working in .NET and as far as I can tell the only choice for key derivation is PBKDF2-HMAC-SHA1. SHA1's output size is only 160 bits. But I am implementing authenticated encryption and thus ...
0
votes
0answers
23 views

key hierarchy management and master key

I have this equation, $E_{K_{as}}(E_{K_{bs}}(K_{ab}))$ which means $K_{ab}$ is encrypted by $K_{bs}$ then whole packet is encrypted by $K_{as}$. I think the key structure is $K_{as}$ is the master ...
0
votes
1answer
31 views

The role of the dealer in visual cryptography

In visual cryptography schemes (VCS), there is special person called dealer. The dealer sets up the system, and the only one who knows about secret image. After encryption, the dealer distributes the ...
1
vote
0answers
41 views

Why is Siphash-128 considered “experimental”?

Why is Siphash-128 still considered "experimental"? What does this mean?
0
votes
1answer
43 views

Key Hierarchy and key Encryption

If i have two 56-bit DES keys, and I use these two key to encrypt a 256-bit AES key. Like this $K_{AT}$ encrypts $K_{BT}$ and $K_{BT}$ encrypts $K$ What is the effective security of key $K$? Is it ...
0
votes
1answer
33 views

Passive adversary and active adversary capability?

I am a newbie of this topic. I have trouble understanding what exactly are the capabilities of passive adversary/active adversary in real world and ideal world.
1
vote
2answers
84 views

Verifying Without Knowing Key

Say user Bob sends an encrypted message to a server. People can download the message from this server and later get the key directly from Bob. Is it possible for the server to somehow verify that ...
4
votes
4answers
114 views

How to construct a collision resistant hash function that is not a one-way function?

How to construct a CRHF (collision resistant hash function) that is not a OWF (one-way function)? Not sure but I think it probably needs another CRHF?
1
vote
1answer
45 views

Deriving 256-bit key from PBKDF2-SHA1

I am working in .NET and their PBKDF2 only uses SHA-1. I am using it to, given a user-supplied password and random salt, generate a 256-bit AES key. The plaintext is encrypted with the AES key and ...
3
votes
1answer
45 views

Updating the seed key of a PRNG while maintaining initial entropy?

Consider a seed key ($n$-bit long) is completely random and entropy of random variable is $n$ and PRNG is using deterministic algorithm and that that deterministic algorithm does not add any entropy ...
8
votes
0answers
96 views

Turing's (still?) classified inference engine algorithm?

Does anyone know the algorithm used by Turing's Colossus inference engine, so highly classified that the Brits kept it secret for decades after WW II? Indeed, it may still be classified. Several ...
1
vote
1answer
35 views

Are the definitions of IND-CCA secure and of IND-CCA secure under standard model identical?

Suppose there is a public key cryptosystem based on the discrete logarithm problem and let this cryptosystem be IND-CCA secure under standard model. Does this statement mean that the given ...
1
vote
0answers
20 views

How do I prove the tracing part in a ring signature model?

I have a question about the article “efficient and multi-level privacy-preserving communication protocol for VANET” by H. Xiong et al. I need the ID of malicious vehicle, but I could not prove how I ...
1
vote
2answers
144 views

How to crack unknown 8-bit encryption algorithm?

Can anyone tell me how to crack the encryption of 8 bit algorithm, when you have some clue that CBC mode is used, but the algorithm is secret. You also have some encrypted data (chosen plain text), ...
3
votes
0answers
42 views

Quantifying bit security for smart-vercauteren encryption scheme

I am working on project that requires to compare in terms of security between two encryption schemes, one of them is the SV scheme. However, I dont know what are the steps exactly towards quantifying ...
3
votes
2answers
45 views

Is Schannel supposed to use SHA1 for (EC)DHE params?

I captured a TLS 1.2 handshake on my server (WIN2012.R2/IIS 8.5) and noticed that SHA1 is being used to hash ECDHE parameters despite both the server and client(s) supporting SHA2 signatures. ...
0
votes
1answer
24 views

How to run a (provably probably) secure global referendum?

The following question is extremely broad and speculative, for which I apologize, but it strikes me as exceedingly important, so I will ask it nonetheless. Suppose an event of global significance ...
-1
votes
0answers
27 views

How to perform collision attack [duplicate]

If I have a table that has many HASHs for some data, is it possible to guess some data by using collision attack i.e. if I used brute-force on the output of 32-bit hash algorithm and find matching ...
6
votes
2answers
94 views

Is there a theorem to determine the elliptic curve parameters based on the group order?

By Hasse's theorem we know that range of the group order of the elliptic curve. And similarly, there exist a theorem on the admissible order of elliptic curves. Suppose by the theorem on the ...
7
votes
3answers
175 views

Generating random non-repeating numbers from a small group

I read this Q&A which gave a clever solution: feed an incrementing index into a block key cipher as a way of producing non-repeating random numbers. The problem is the block size of all the good ...
1
vote
0answers
22 views

Are the prime numbers used for RSA encryption known? [duplicate]

I read that one reason why RSA is secure is because it uses a huge number that's called the modulus which is the product of two prime numbers. For maths reasons the prime numbers being prime numbers ...
-1
votes
0answers
34 views

Which are similar encryption techniques as honey encryption?

I was reading about this technique called "Honey Encryption." Can someone suggest encryption techniques similar to honey encryption? To know more about honey encryption please refer the link ...
4
votes
2answers
120 views

Integer factorization still hard with Hamming weight hypothesis?

Consider the following problem: Factorize a $n$-bit integer $c$ knowing that it is the product of two integers with known Hamming weight $h$. Is there a way to prove that this is still hard? I have ...
0
votes
0answers
19 views

Can you have partial cryptographic obfuscation (without a trusted setup)?

Cryptographic Obfuscation is a powerful cryptographic technique. My question is, can you do it partially? Instead of obfuscating an algorithm completely, you can have an algorithm with a couple of ...
3
votes
1answer
34 views

Two or more initialization vectors with the same key

I'm studying about WEP and I'm in doubt. It seems that because it uses a initialization vector of 24 bits, which is relatively short, is easy to determine which key was used to encrypt the data. But ...
-1
votes
0answers
45 views

Meaning of “random n/2 bit prime length prime p”

iam trying to solve a homework for the subject "system security" at university. For my question iam referring to this document: Solution to the Millionaire's Problem Could you please tell me why in ...
5
votes
1answer
47 views

State of the art low memory arbitrary-domain PRP?

I am wondering what the state of the art is on low memory arbitrary-domain PRPs. That is, I'm looking for an algorithm that implements bijective function $PRP : \mathbb{Z}_n \times \{0, 1\}^b ...
0
votes
0answers
19 views

If one has hash = hash(salt + password) and one knows N pair of hash and salt is it easier to attack the password?

For example: $hash = md5($salt + $password) I know N pairs $hash $salt 60d0c34a37a71b279edaae4ffdcba86d 1 1d79c99d01f51f8e8b4c6505e8f6728e 2 ... Is it possible ...
1
vote
1answer
41 views

Security implication of deriving key with fixed salt for files authentication

Context: I need to calculate MAC for a collection of files just for future integrity and authentication verification. This is the conceptual order of steps: Derive a 64 bytes key from user input ...
0
votes
0answers
25 views

How is Extended Euclidean Algorithm related to Approximate-GCD problem?

I had a doubt regarding the connection between the Extended Euclidean Algorithm and the Approximate-GCD problem. Are there any relations? i.e., the hardness of A-GCD is derived from EEA. Is there any ...
3
votes
2answers
55 views

How to implement 1-out-of-n OT from 1-out-of-2 OT?

How can I implement a 1-out-of-$n$ oblivious transfer protocol from 1-out-of-2 OT protocol which is resistant against passive corruption? Assume we can access 1-out-of-2 OT $n$ times.
0
votes
1answer
44 views

Security of DGHV Encryption

In DGHV Security How to get reliable oracle for least significant bit and then uses binary GCD algorothm that uses reliable oracle to find secret key p.Also what is oracle. Is this a turing ...
-1
votes
0answers
41 views

Is the following obfuscation weak in security or not?

$q=$large prime number secret key=$(x,z)$ $f(x,z)=(x/z)* y$ , to hide $y$ $x \leftarrow (1,2,3,...,q)$ $z \leftarrow (1,2,3,...,q)$ $y \leftarrow (1,2,3,...,q)$ Is the obfuscation function $f(x,z)$ ...
1
vote
1answer
49 views

Differences between OWP and OWF and their IND-CPA security

I am learning about one way permutations and one way functions and am not sure of the differences if there are any. Also in the random oracle model are they both IND-CPA secure?
1
vote
0answers
46 views

Given a public-key encryption and signature scheme, define a new primitive

I'm new to cryptography and am currently working on the following question: Say you are given a public-key encryption scheme $\Pi_e=(\mathcal{K}_e,\mathcal{E},\mathcal{D})$ and a signature scheme ...
1
vote
1answer
29 views

Would A5/1 with a much larger state be a good choice of stream cipher for hardware?

Would A5/1 with a much larger state be a good choice of stream cipher for hardware? Assume that a reasonable choice of MAC is made such as GMAC, with the first 128 bits of the stream cipher output ...
0
votes
1answer
51 views

Is AES-CTR or ChaCha20 vulnerable to a time-memory trade off?

Is AES-CTR or ChaCha20 vulnerable to a time-memory trade-off attack? According to this paper it seems to be, which would put AES-CTR at a clearly breakable $2^{64}$ security level (for AES-128-CTR). ...
0
votes
1answer
105 views

Two-party equality computation

Alice and Bob each secretly chooses an integer between 1 and 10, a and b. They want to know (with high probability) whether or ...
0
votes
1answer
32 views

Subscript R notation for the finite fields

I'm trying to understand the notation used in the literature for Pairing-based cryptography. I know (and I hope I've understood it well) from Wikipedia that $\mathbb{Z}_p$ is the finite field of ...
-1
votes
1answer
51 views

can pdfcrack software crack a 128 bit encrypted pdf file

One day ago,i downloaded a pdf that requires password then i search a software to decrypt the password that's s/w called pdfcrack Then i install pdfcrack and run a cmd in terminal pdfcrack -f ...
0
votes
1answer
28 views

Is it possible for the Rho method against an Elliptic Curve to take more than the sqrt of the total state space?

Is it possible for the Rho method against an Elliptic Curve to take more than the sqrt of the total state space? It the reason why this is not generally done because of a meet-in-the-middle attack?
3
votes
2answers
60 views

A bijective hash function

Suppose: $H: \{0,1\}^{n} \rightarrow \{0,1\}^{n}$. $H$ is bijective. It is difficult to derive $x$ from $H(x)$. Is this type of function possible? What would the strength of it be? I realize that ...
1
vote
1answer
25 views

Multiplexed stream cipher

Consider the stream cipher that consists of 3 LFSRs, with the output of one coming being used to determine which of the other 2 is used that clock cycle. Both the IV and the polynomials are secret. ...
3
votes
1answer
43 views

(How) Can we use HOTP for file encryption?

I recently went through the list of available KeePass plug-ins and noticed one that advertises support for HOTP as a means to derive the database key. Now I trust the developer of this plug-in who is ...
1
vote
1answer
27 views

Encryption strength when using a PBKDF

Suppose: $m$ is a positive integer. $n=2 \times m$. $H: \{0,1\}^{*} \rightarrow \{0,1\}^n$. $p$ is a password. $s$ is a salt. $K=\{0,1\}^n$ is the derived key. $PBKDF(p,s)$ derives a key from $p$ ...
-3
votes
1answer
88 views

How to Perform Computation on AES Encrypted Data

I have this code that successfully performs symmetric encryption using AES algorithm. How can I go about performing computation on it to achieve somewhat homomorphic encryption? ...
3
votes
1answer
68 views

How to prove hardness of approximate-GCD problem?

I am trying to prove the security of my system using the hardness assumption of the approximate-GCD problem using contradiction, i.e. If the attacker is able to break in our scheme, then attacker ...
3
votes
2answers
539 views

Why can't we use the first block of AES-CBC as MAC

As per topic, why can't we use the first block as MAC instead of using the last block? what's the rationale?
0
votes
1answer
36 views

Robust combination of two Password Based KDFs

I am researching some different constructions for combining two Password Based Key Derivation Functions in a robust manner to prevent weaknesses in a single algorithm from reducing the security of the ...

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