Cryptography Stack Exchange
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1500 questions
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4 answers

How can C rand() be exploited if a secure seed is used?

I've just started doing a research project on CSPRNGs and I would like to know what kind of vulnerabilities a regular PRNG has with a secure seed. For example, if I generate a random number using LavaRnd to seed srand(), then generate some big key…
Jacob H
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What is the difference between signatures and VRF?

For example we have asymmetric signature scheme(RSA or ECC based) and VRF(also can be RSA/ECC based), both of them can be verified using public key of the signer/hasher and also are unique for each message. So what is the difference?
Kesha
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2 answers

Why do we keep designing new static s boxes?

As I understand s box properties, they primarily need high non linearity and low auto correlation. But most importantly for this question, they're not secret. There are many questions on this site asking for help in generating them. And new…
Paul Uszak
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What's the difference between polylogarithmic and logarithmic?

I can't imagine one that is not polylogarithmic but logarithmic. $O(\log N)$ satisfies both. What about $O(\log^{3}N)$, $O(\log^{100}N)$, and $O(\log^{10000}N)$ ? Let's say $N=10^{10}$
mallea
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12 answers

Are one-time pads crackable in theory?

I've been taught that one-time pads are the only perfect encryption since the only way to recover the message is by knowing the key. For example, for a target bitstring of 100 bits, I cannot scan all bitstrings of 100 bits and XOR each with the…
yters
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17
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5 answers

Creating your own encryption and decryption algorithm

I'm very uneducated when it comes to cryptography. I have tried to find an answer to my question, but what I've read doesn't quite cover what I'm asking. I have thought up my own encryption algorithm (which I'm sure is nothing new) and I would like…
user1575550
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What is the key size currently used by RSA and Diffie-Hellman for secure communication over Internet?

What is the key size that RSA and Diffie-Hellman are using now that can guarantee secure communication over Internet and will not be able to break by the best available algorithms (NFS & FFS or any others) in feasible time?
Tanmay Sharma
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4 answers

How is the quality of a password calculated and what does it mean?

While using Keepass and using it to generate random passwords, I always have noticed the "quality" section but truthfully have never known what it actually means. So my questions are; How much entropy is enough? How much is overkill? How does…
Shackrock
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How does one calculate the scalar multiplication on elliptic curves?

I found this example online: In the elliptic curve group defined by $$y^2 = x^3 + 9x + 17 \quad \text{over } \mathbb{F}_{23},$$ what is the discrete logarithm $k$ of $Q = (4,5)$ to the base $P = (16,5)$? One (naï­ve) way to find k is to…
Keith Lau Si Keit
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Can double-encrypting be easier to break then either algorithm on its own?

As was pointed out in Martin Bonner's comment I cannot prove this, but it seems intuitively impossible. An encryption function is supposed to obscure the plaintext to the point where no information can be obtained about it. If the underlying…
Shelvacu
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2 answers

Is bcrypt better than GnuPG's iterated+salted hashing method?

GnuPG has slow hash built-in in form of iterated+salted S2K. Does it have disadvantages in comparison with bcrypt or scrypt? Is GnuPG's slow hash method easily automated in GPUs?
Andrei Botalov
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1 answer

S-box design criteria and random sboxes

What are the disadvantages of using random s-boxes? In AES, the s-boxes had to obey certain mathematical rules, which? And why? What security does using hidden s-boxes (GOST) or generating them from the key (Khufu) add?, and how do these secret and…
Devros Exrix
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3 answers

Information about RSA key pair generation with backdoor?

Someone posted an article on Reddit a few days ago, and I haven't found much about it except for links back to the same page. And for a brief summary, essentially, it's possible to introduce a backdoor during RSA key generation. For example, to…
Daffy
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2 answers

Status of Algebraic Eraser key exchange?

Algebraic Eraser™ is a relatively new asymmetric key agreement protocol (also designated the Colored Burau Key Agreement Protocol), based on a simultaneous conjugacy search problem in a braid group. An initial exposition is: Iris Anshel, Michael…
fgrieu
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Is there a standardized tree hash?

SHA-1, SHA-2, and the standardized version of SHA-3 are all sequential. This is impractical for hashing very large files distributed across machines. Any sequential hash can be straightforwardly converted into an efficiently parallelized hash…
Geoffrey Irving
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