0
votes
1answer
72 views

Doubts about Authenticated Data Structures logic

I am studying the theory of authenticated data structure, like Merkle Tree and I have a doubt: why use them? I explain better: why to be sure, for example, that a cloud provider didn't modify my files ...
5
votes
0answers
77 views

Rule 30 Cellular Automaton for Cryptography

Steven Wolfram of Mathematica uses a pseudorandom number generator based on Rule 30 for applications in Mathematica software but I would like to know if a pseudorandom generator based on Rule 30 is ...
4
votes
1answer
64 views

What is the difference between MACTripleDES and TripleDES?

I was asked to encrypt/decrypt a string using MACTripleDES. Is there any difference between MACTripleDES and TripleDES? If, where exactly is the difference between both?
2
votes
3answers
96 views

2 Part Encryption

Can anyone tell me if an encryption / decryption scheme like the following exists? Encrypted1 = SomeCryptoFunction(Data, Key1) ...
7
votes
3answers
2k views

Where can I get information on how to implement AES?

I want to write AES from scratch without using the built in libraries of java. I know there are hundreds of AES programs (and websites) out there but I can't seem to find a site that gives me the ...
5
votes
2answers
63 views

Protocol to identify zone of potential agreement without revealing reservation prices and having to trust third parties?

A wants to buy a company from B. Before A and B enter negotiations, they want to make sure that there actually is a zone of potential agreement. Obviously, they don't want to communicate their ...
4
votes
0answers
84 views

Adding parameters to sponge's capacity

Is it safe to XOR parameters like domain, length of the message or block counter into sponge's capacity or that gives attacker control over capacity? For example NORX XORs domain into capacity. Does ...
1
vote
0answers
26 views

Simple RSA Key Generation example [duplicate]

I have two prime numbers: p = 37 q = 41 And I need to find whether any of these prime numbers, 5, 7 or 11, can be used as a valid encryption key e? My working ...
1
vote
0answers
36 views

how to change math.random() implemented in javascript to securerandom [closed]

In Javscript code in one of our application,I am trying to change Math.random to secure random.I am not sure ,how to change.can anybody help?
1
vote
1answer
52 views

Finding collisions for the DES F-function

It's known that for a given subkey, the F-function of the DES is not injective (see Is the DES F-function injective for a given subkey?). I am interested in efficiently finding collisions for this ...
6
votes
1answer
399 views

How do you construct a practical full-domain hash function?

I am looking for practical constructions for Full Domain Hash. I have read Random Oracles are Practical by M. Bellare and P. Rogaway, the construction suggested on page 8, under "Uniformity: a ...
3
votes
1answer
194 views

Homemade Randomized RSA

Considering the following encryption scheme where RSA is used to encrypt a plaintext m and then we choose a random r and compute: $$A = r + m^e \bmod N$$ and $$B = r^e \bmod N$$ So the ciphertext is ...
5
votes
1answer
61 views

Question about lower bound and upper bound key collision

I'm reading this article and I have a doubt in the page 7. First I going to describe the required definitions and next I formulate my question. Let be $$F(n)=\{f_k: \{0,1\}^n\rightarrow \{0,1\}^n| ...
8
votes
1answer
359 views

Uniformly distributed secure floating point numbers in [0,1)

Is there any way to generate cryptographically secure uniformly distributed floating point numbers in the interval [0,1)? For example, in Javascript, there is ...
5
votes
0answers
98 views

Proof that perfect privacy implies that the number of keys is at least the number of messages

I was reading a proof to the statement: Perfect privacy implies that $|K| = |M|$ where I am pretty sure that $K$ is the set of keys and $M$ is the set of messages. The proof is the following, ...
1
vote
0answers
113 views

Which crytographic standard were RC5, CAST5 and Blowfish based on? [closed]

Which crytographic standard were RC5, CAST5 and Blowfish based on? A. AES B. RC2 C. 3DES D. DES
0
votes
0answers
14 views

Known plaintext, ciphertext, encryption method (AES CBC) and IV (static) [duplicate]

I know the plaintext, the ciphertext, the encryption method (AES CBC) and the IV -- which is static. While not able to perform a chosen plaintext attack per se, I can obtain many known ...
0
votes
2answers
135 views

NIST tests for AES [closed]

How to do the benchmarking of a self implementation of AES algorithm using NIST test suites? I am unable to find enough material on the internet regarding this.
4
votes
0answers
38 views

Finding differentials and space complexity

Most of article about differential cryptanalysis present the generic method, the way to find sub keys. But I can't find a clear explanation about how to find the differentials used in examples. In ...
2
votes
0answers
59 views

Convert messages to elliptic curve points [duplicate]

Let $E$ be an elliptic curve; $\alpha,\beta$ two points of $E$; and $a$ a private key such that $\beta=a\cdot\alpha$. We choose random integer $k$ and plain text $x\in E$. Encryption and decryption ...
5
votes
1answer
188 views

Zero knowledge proof of shared secret

Alice holds a secret $a \in X$. Bob holds a secret $b \in X$. Is there a protocol that lets them compute $f(a, b) = \begin{cases} 1 & \textrm{if } a = b \\ 0 & \textrm{else} \end{cases}$ If ...
3
votes
1answer
535 views

How to prove that a function is not pseudorandom?

I am currently enrolled in a cryptography course, which uses the book by Katz and Lindell. I'm struggling with the exercies which ask for proofs, like the following one: Let G(k) be a PRG with ...
6
votes
2answers
121 views

Effect of $L_n[1/4,c]$ integer factorization on RSA-2048

Using the L-notation, integer factorization of an integer $n$ has the best known complexity of $L_n[1/3,c]$ using general number field sieve. Would discovery of an algorithm with complexity ...
10
votes
2answers
3k views

AES Key Length vs Block Length

This answer points out that certain key and block lengths were a requirement for the AES submissions: The candidate algorithm shall be capable of supporting key-block combinations with sizes of ...
21
votes
6answers
2k views

Is it feasible to build an index of prime factors?

Would it be possible to break an RSA key, in for example 1 week of time, if the cracker have already spent X number of years building an index of primes by performing every permutation of existing ...
2
votes
1answer
101 views

Multiple levels of encryption

Is it feasible to have data encrypted at different levels of hierarchy I'd like to encrypt an xml database (such as used in www.keepass.info) whereby two or more keys can exist. For example: Key #1 ...
2
votes
1answer
104 views

Is secure lattice based cryptography in future?

Lattice cryptography is a post quantum cryptography that work on two NP-hard problem in below: Find shortest nonzero vector from origin and Find minimum distance of a arbitrary point out of lattice ...
0
votes
0answers
26 views

Finding Private Key $d$ using RSA [duplicate]

I'm a RSA n00b when it comes to the mathematics for RSA. After spending some time reading, watching lectures, etc. I pretty much have everything down, except for how to figure out the equation for ...
2
votes
1answer
40 views

Winternitz Signature in standard model

I am studying the Winternitz signature and I describe its algorithms in the next W-OTS Key Generation. Select the parameter $w\geq 2$ that is the bit size of the partitions of the message to be ...
4
votes
2answers
726 views

What does “Worst-case hardness” mean in lattice-based cryptography?

In the wiki page of Lattice-based Cryptography the "Worst-case hardness" is defined as below: Worst-case hardness of lattice problems means that breaking the cryptographic construction (even with ...
5
votes
1answer
120 views

Proof of RSA security dependent on public key exponent

I am writing a (high-school) paper on the public key exponent's (in textbook RSA - no padding is discussed!) significance in terms of time and security. The time part is done; as for the security ...
6
votes
2answers
930 views

Could an HMAC be used as a hash?

MD5 is considered broken and SHA-1 is closely following, but HMACs built around either are still considered relatively secure. It makes me wonder if MD5 and SHA-1 HMACs can be used as secure hashes. ...
2
votes
4answers
4k views

How can a Vigenère cipher be broken if the message is short?

I was watching a Stanford lecture on Vigenère cipher and in it the professor said that – to break the cipher – we assume the length of the key is known. We then break the cipher into groups of this ...
1
vote
1answer
54 views

What is the viability of a hybrid vigenere cipher?

So a vigenere cipher's main weakness is that you can use frequency analysis on each alternated alphabet, and thus crack the cipher with relative ease... But that implies that you know what the ...
4
votes
2answers
78 views

Importance of random number generation in Schnorr's signature

In Schnorr's digital signature protocol (https://en.wikipedia.org/wiki/Schnorr_signature), the signing process (as described in wikipedia) requires the generation of a random bit $r$. I am wondering ...
8
votes
0answers
79 views

K friedman - two texts explanation

I have a question, I read the k friedman test to determine the period of a vigenere cipher text, and I understand something like this: Friedman's K test tries to find out what period of the cipher by ...
1
vote
1answer
95 views

Would it be better to use HKDF or SCrypt for deriving a child key?

Okay so I'm trying to derive a child public key from an EC public key. I've come up with a couple ideas and now I'd like to know which is more secure. Mp: The master key pair, this includes a ...
32
votes
3answers
448 views

How does RSA compute such enormous numbers?

So I have been reading and learning a lot about cryptography lately and in particular asymmetric ciphers such as RSA. One thing that I am curious about but never seems to be mentioned is how the ...
1
vote
1answer
116 views

How “hard” it is to take an e'th root mod p?

I know it's hard to find the $e$th root of a number mod $n=p_1*p_2$, and if it would be possible we could break RSA. But how hard it is to take an $e$th root mod $p$ where $p$ is a prime and ...
3
votes
1answer
118 views

Counting points on elliptic curve over binary field

How to count number of rational points on elliptic curve over binary field?
6
votes
1answer
236 views

What advantages does Keccak have over Blake-2?

Keccak/SHA-3 is new NIST standard for cryptographic hash functions. However, it is much slower than Blake-2 in software implementations. Does Keccak have compensating advantages?
4
votes
2answers
461 views

Can elliptic curve (25519) be used to encrypt file?

This is probably a simple question, but I haven't been able to see it stated anywhere. Is it possible to directly encrypt a file (of any length) with some form of EC using the 25519 curve. I know ...
2
votes
1answer
294 views

Authenticated Encryption of UDP packets

I am working on a UDP based file transfer protocol. Congestion Control, Resending of packages and other UDP challenges are dealt with - speedtests shows that the protocol is up to 10 times faster than ...
-1
votes
1answer
82 views

NIST PRIMES - cryptography

I have a problem, If I have $p = \text{P-192} = 2^{192} - 2^{64} - 1$ with the base $2^{64}$ so, $2^{192} \equiv 2^{64} + 1 \pmod p$ the same that $(p=\text{P-192})$ or $2^{256} \equiv 2^{128} + ...
4
votes
0answers
50 views

What is the correct definition of the blowfish F-function?

The Blowfish cipher uses a so called F-function which uses S-Boxes (S[i], i=0,1,2,3) to ...
3
votes
1answer
103 views

Encrypt-then-authenticate variant used in IPsec

I am trying to understand the variant of Encrypt-then-Authenticate (EtA) that is used in IPsec. For this I have looked at this chapter. What I got so far is that the integrity and confidentiality ...
4
votes
2answers
241 views

Why is 2048-bit RSA always paired with 320-bit ECC?

You may already have noticed that most smart cards ship with 2048-bit RSA support and 320-bit ECC over GF(p) support. You may have already asked yourself "why exactly 320-bit?". Now I remember having ...
4
votes
1answer
68 views

Is it wise to use HOTP (raw bytes) as a key for HMAC?

Assume I have client and server applications with a shared master secret KEY_SECRET already in place. Also assume that the client and server have an implicit shared ...
2
votes
1answer
143 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 ...
2
votes
2answers
72 views

Is the security of an HMAC equally important as the security of the cipher itself?

I'm a little unclear on how hash based MAC works... So I would like to know, is the security of your hash function as important as the security of the overall cipher? Basically, if you can crack the ...

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