Latest Crypto related questions

Score: 2
DiamondDuck avatar
What are some use cases for signature scheme that can only sign finite amount of time?
hu flag

From one-time hash-based signature, one can convert it into 2^d time signature by using Merkle hash tree.

However, it seems to be a trick that enables multi-time signing.

My question is: is there any use case for a signature scheme that can only be used to sign for a fixed number of time (punch/redeem card)?

Score: 0
storing private key on the client-side (with and without Web Cryptography API)
pk flag

I'm trying to understand what are my options(and best practices) regarding storing private key on the client-side.

There's a Web Cryptography API that can generate pair of keys with non-extractable abilities. I don't know exactly what it means, but I couldn't find a way to use it with my own pair of keys(private/public) anyways - is it even possible?

How can I implement something similar to it by mys ...

Score: 1
John Pham avatar
Question about Harden and Normal Key derivation
vn flag

I am reading about Hardened and Normal child key in chapter 5 of the book "Mastering Bitcoin" by Andreas, along with this detailed thread and BIP-32. Here are some of my understanding about these two procedures:

k: private key // K: public key // i index // c chain code // H HMAC hashing result // Hleft the first 32 bits of the hash result. // n order of Elliptic Curve. // G starting point of Ellipti ...

Score: 1
zxcv avatar
How to prove reduction from decision to seach LWE?
cn flag

I am new to cryptography, and trying to understand the concepts of LWE (learning with errors) formally. I will state my understanding of the definitions, which might be incorrect.

Definitions According to My Understanding

Let $R$ be a finite unital commutative ring equipped with a probability $\mu$ (whose $\sigma$-algebra is discrete). $R$ is said to satisfy the worst-case search LWE assumption i ...

Score: 3
Will Hashing Multiple Times Be More, Less, Or Similarly Secure As Hashing Once
br flag

Will Hashing Multiple Times Be More, Less, Or Similarly Secure As Hashing Once?

Flushing out this question:

  • I saw this claim:
    • List item: Don't do this: hash = sha512(password + salt); for (i = 0; i < 1000; i++) { hash = sha512(hash); // <-- Do NOT do this! } however if you are going to double hash then do this hash = sha512(password + salt); for (i = 0; i < 1000; i++) { hash = sha512( ...
Score: 1
Yang avatar
1-out-of-2 OT, chosen 1-out-of-2 OT and Random 1-out-of-2 OT
cn flag

I'm studying some concepts about Oblivious Transfer(OT), and would like to know what is the 1-out-of-2 OT, chosen 1-out-of-2 OT and Random 1-out-of-2 OT, and wonder the relation and difference between these concepts, thank!

Score: 1
Is it secure if a secret key is used in the function of a functional encryption?
uz flag

In my scheme, two functional encryptions FE1 and FE2 are used. The function f1 corresponding to FE1 is as follows:

f1_y(x)
{ hardwired msk2
  output  sk2 = FE2.KeyGen(msk2, (x, y))
}

where msk2 is the master key of FE2.

Then, the user obtains the private key sk1_y=FE1.KeyGen(msk1, y). For any ciphertext c=FE1.Enc(x), the user can obtain a new private key sk2 = FE1.Dec(sk1_y, c).

Is it secure that  ...

Score: 2
Sheldon avatar
What's the meaning of without loss of generality in cryptography?
nl flag

What's the meaning of without loss of generality in the cryptography (Zero Knowledge Proof)?

Without loss of generality, suppose we want to check if a 1 = a 2 . In the following description, j ∈ { 1, 2 } .

Reference: Zero-knowledge test of vector equivalence granulation of user data with privacy.

Score: 2
How to prove the security if a circuit is obscured by an IO,where the key generattion algorithm of a functional encryption is used in the circuit?
uz flag

I want to design a scheme, where there is a circuit C0 which is obscured by an indistinguishability obfuscation (IO). In C0, a master key of a functional encryption (FE) is hardwired. Given an input z to C0, it outputs a secret key using the key generation algorithm of FE. C0 is as follows:

C0(z)
{ hardwired: msk
  output sk = FE.KeyGen(msk, z) 
}

Then, C' = IO(C0) is given to the user. With C', the u ...

Score: 3
js wang avatar
About simulating abort in multiple party computation
cn flag

I am new to the simulated proof and am a little bit confused about the abort in the simulation.

When the real-time protocol abort, I assume that the ideal process should also abort? Does this mean that the simulator would first observe the result of real-time protocol, then decides what to run to reach abortion?

Sorry, it may be a little bit vague in my description; here is a example:

When the simulato ...

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