Latest Crypto related questions

Score: 1
Belphegor avatar
What is ECDH used for in BLE Authentication?
in flag

I am currently new to the world of BLE and I came across this article which mentions ECDH.

In the diagram in part $3$, it generates the DHKey/shared secret (I am assuming this is the correct terminology based on google search) , but then once it's generated the diagram never references it ever again. What exactly is the point of it in this diagram? I know the shared secret is used to encrypt the l ...

Score: 0
How does biometric authentication add protection to encryption schemes?
us flag

I'm wondering since at least 2 offline password management services,Passkeep and Keepass both use biometric authentication in addition to the master password. You need to possess the physical device to login to those 2 services,but if the attacker already posseses the device how would biometric authentication protect the user from accessing the key and encrypted data or whatever sensitive data they migh ...

Score: 0
Senshi avatar
Pseudonymization hashing using public key
be flag

I have logs containing sensitive data (mail addresses, usernames etc.) that need not only be made GDPR compliant, but in general be secured as best as possible, so anonymization/hashing would be an easy solution. However, at the same time I need to be able to correlate the information for monitoring purposes (e.g. identifying attacks). For that, the plaintext values are not relevant, but I need the pseu ...

Score: 1
Star Seller avatar
Security of anonymous group credential issued over multiple user secret keys plus a common/public system message
gl flag

In a group signature scheme based on Pointcheval-Sanders (PS) single-message signature, the anonymous credential $(\sigma_1,\sigma_2)$ issued by the group manager (GM) with secret key $sk = (x,y) \in \mathbb{Z}_p^2$ and public key $pk = (\tilde X,\tilde Y) \leftarrow (\tilde g^x,\tilde g ^y )$ to a user $\mathcal{U}_i$ with a single secret key $sk_i \in \mathbb{Z}_p $ is computed as $(\sigma_1,\sigma_ ...

Score: 1
user avatar
Why do we need both bitmasks and keyed hash in SPHINCS+
va flag

I think one of them is related to multitarget attacks and the other is related to collision attacks. But I cannot find how hash based crypto related to hash collisions.

1-) Consider the following Lamport one time signature scheme

  • Assume a 128 bit hash function $H$ is used
  • Randomly choose $p_i$ and $r_i $ for $1\leq i \leq 128$
  • $SK=\{(p_i,r_i)\}_i$ is the secret key and $PK=\{(H(p_i),H(r_i))\}_i$ ...
Score: 1
IS there a way to do zk proof on string?
eg flag

For example: "I am a very secret person".

I'd like to show someone that this string includes 'secret' without revealing the rest of the string. Is there anyway?

Score: 1
Dominic van der Zypen avatar
Inverses of the operation $(a,b) \mapsto a \oplus b\oplus ((a \land b) \ll 1)$ for fixed bit length
br flag

Background. In their paper about the cryptographic scheme NORX, the authors use a fast approximation of + by bitwise operations (taking fewer CPU cycles than proper addition) using the formula $$a+b \; \approx \; a \oplus b \oplus ((a \land b) \ll 1)$$ where $\oplus$ is bitwise XOR and $\land$ is bitwise AND, and $\ll$ is left-shift by 1 position. (The purpose of $((a \land b) \ll 1)$ is to simulate th ...

Score: 1
zxcv avatar
"randomized" indistinguishability vs "deterministic" indistinguishability
cn flag

Let $X$ be a measurable space. For each $n\in\mathbb N$, let $P_n$ and $Q_n$ be probabilities on $X$. We say that $(P_n)_{n\in\mathbb N}$ and $(Q_n)_{n\in\mathbb N}$ are statistically indistinguishable iff for all measurable set $E\subseteq X$, the function \begin{equation} n\mapsto |P_n(E) - Q_n(E)| \end{equation} is negligible.

But what if we allow "randomness"? Let's say that $(P_n)_{n\in\ ...

Score: 0
How to ensure files on client computer haven't been tampered with by client?
ro flag

I'm designing a program that clients can download to the computer. This program needs to sync with my online server on a regular basis to confirm that the client's Activation Code hasnt expired and they're paying their bills. However, I want the program to be able to run for a period of up to 5 days without having to connect. This would allow the client to use the program for a time if they lose their i ...

Score: 4
I don't see how a ECDH is useful
ph flag

I'm having a hard time understanding the usefulness of using an ECDH over traditional asymmetric encryption. Both parties have to exchange public keys to compute the ECDH, so why wouldn't they just encrypt their messages with the public keys they just exchanged?

The only use case for ECDH I can think of is if Alice loses her original message after sending it to Bob, with ECDH she can still decryp ...

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