1
vote
1answer
33 views

Can I always derive a key pair from password+salt with libsodium?

I'm using libsodium to create public/secret key pairs from a password and salt combination by using crypto_pwhash_scryptsalsa208sha256 to generate a seed and ...
6
votes
1answer
62 views

Is the 'nonce' in bitcoin really a nonce?

Is the 'nonce' in bitcoin really a nonce? Reading definitions of nonce and salt it seems the number is used as a salt but the same value can occur in multiple blocks; there's no requirement or indeed ...
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 ...
1
vote
0answers
54 views

Calculating the discrete logarithm

I'm given a prime number $p = 1217$ I'm also given the following equations: $$ 40 \equiv \log2 \pmod{64} \\ 63 \equiv \log3 \pmod{64} \\ 13 \equiv \log5 \pmod{64} \\ 13 \equiv \log2 \pmod{19} \\ 10 ...
-1
votes
0answers
32 views

AES-CMAC in Java Card

Hello I am new to the world of Java card programming. Is there a proper way of doing an AES CMAC encryption? After researching I've hit a roadblock wherein I cannot find any example or samples of Java ...
1
vote
2answers
145 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), ...
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.
0
votes
0answers
10 views

ACM 2004 World Finals, problem D: how can I solve this using a brute force method? [migrated]

https://icpcarchive.ecs.baylor.edu/external/29/2996.pdf How can I solve this using a brute force method in Python? I want to use a nested for-loop for the parameters I'm just not sure where to go ...
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
1answer
66 views

A simple client/server authentication protocol

Some days ago I asked for a help to find and correct the problems of an authentication protocol. I closed the post because I was convinced I can correct it but, unfortunately I'm having some troubles. ...
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 ...
4
votes
2answers
233 views

Why does the modulus of Diffie–Hellman need to be a prime?

I read a lot about Diffie-Hellman, but there is one thing I dont understand: why does the modulus p need to be a prime? What if it would not be a prime?
7
votes
2answers
165 views

Can the Smart-Vercauteren Homomorphic Encryption be implemented as a practical fully homomorphic encryption scheme?

Smart and Vercauteren proposed a homomorphic encryption scheme (PKC 2010) following Gentry's principles. ​ Though their scheme can achieve fully homomorphism theoretically, they admitted that "for ...
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
votes
0answers
24 views

Pairing on BN curves, GMP code

Is it possible to write a small implementation of tate pairing using BN curves using GMP. It does not need to be efficient. I just want to understand the steps. Thank you.
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 ...
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 ...
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 ...
1
vote
0answers
41 views

Why is Siphash-128 considered “experimental”?

Why is Siphash-128 still considered "experimental"? What does this mean?
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 ...
9
votes
0answers
97 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
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 ...
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 ...
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 ...
3
votes
1answer
115 views

The exact definition of a symmetric encryption

I have doubts for the definition of the decryption algorithm $D(.)$. I think I've already seen that the decryption returns a plaintext $M$ on input the key $K$ and $C=E_K(M)$. I have also seen that ...
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 ...
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
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 ...
6
votes
2answers
88 views

Possible problems in using a hash algorithm to construct a stream cipher

I'll define an example hash-based stream cipher as such: $H: \{0,1\}^* \rightarrow \{0,1\}^{256}$ is the hash function. $K=\{0,1\}^{256}$ is the secret key. $N=\{0,1\}^{128}$ is the nonce. ...
0
votes
2answers
65 views

SHA1 collision for first 32 bits for two different message

Is it possible to create a program to find the collision of 2 different message but with same first 32 bits using sha1 hashing? I tried using a while loop but it run endlessly as though no match is ...
3
votes
1answer
105 views

Why should $a,b < N$ for Montgomery Reduction?

In Montgomery reduction, when calculating $a \times b \mod N$, it is required that $a \lt N$ and $b \lt N$. I think $0 \le T \lt N \times R$ is enough for the Montgomery Reduction. Rationale: Let ...
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 ...
2
votes
1answer
108 views

Using e-ID Number for Encryption and Digital Signing

I want to use e-ID number for performing Encryption/Decryption and Digital Signing - and in order to do so, I've opted a PGP-oriented approach which goes a bit like this. Generating PGP key-pair ...
-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 ...
-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 ...
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 ...
10
votes
1answer
413 views

Compact digital signature for noisy data

The question asks for a signature scheme, with a public verification procedure, that is tolerant to minor alterations of the signed data during its transmission [possibly in analog form over some ...
2
votes
2answers
238 views

How secure is a client-side javascript encrypter?

A friend of mine needed help with her website and asked how to send me her login information securely. I've never known how to do this, so I figured now was the time to learn. After some googling, I ...
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 ...
2
votes
1answer
171 views

What is the meaning of IND-CCA secure under standard model? [duplicate]

I notice that in many research papers (viz. "Universal hash proofs and a paradigm for adaptive chosen ciphertext secure public-key encryption" by Cramer and Shoup) the authors showed that their ...
3
votes
2answers
57 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.
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 ...
2
votes
1answer
208 views

How long does it take to decrypt an RSA/ECB encrypted message?

I am working on assignment where I have specific scenarios and I am little bit struggling with this one. Alice sends and email to Bob.For this e-mail, she uses the following method of encryption: ...
8
votes
1answer
102 views

How do voters verify a Helios (v3) election result?

So from my understanding of verification specification version 3, a Helios election proceeds as follows: A voter retrieves the system's public key to encrypt their vote & submit it. The voter ...
-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 ...
3
votes
2answers
515 views

Encryption of 8 bit of block data

I'm looking for a cryptographic algorithm that allows encrypting only 8 bits of data in a block. Is there any such algorithm that is considered secure? The reason I'm asking is because I have to ...
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 ...
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 ...
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 ...

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