Top new questions this week:
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One of the approaches in order to prevent Sybil or DoS attacks is CPU-bound PoW. However, because of the influence of Moore’s law, the memory-based approaches are suggested.
As actually there are two ...
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I'm trying to understand how differential analysis works. I'm reading this and this tutorials, but it looks like they do different things. In the first paper author tells us to bruteforce last round ...
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I'm given a large prime $p$ and $c \equiv m^e \pmod p$, and $e = 2^{64}$. Typical RSA rules don't apply here, since $\phi(p) = p - 1$ is even, and $e$ is a power of two, so they share a common factor, ...
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Problem statement:
"Bob is a paranoid cryptographer who does not trust dedicated hash functions such as SHA1 and SHA-2. Bob decided to build his own hash function based on some ideas from number ...
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In the paper for curve25519 is described how the prime was chosen. But I don't understand why the biggest 255-Bit prime was chosen instead of a 256 Bit prime. Can someone explain this to me?
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Now that Keccak has been chosen as SHA-3 we see that there have been defined quite a few related modes, including authenticated cipher modes, the KMAC message authentication mode, XOF's and whatnot. ...
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Let the subgroup $G$ of elliptic curve constructed with point $P$ with prime order $q$ by $G=\langle P\rangle $. The $h(x)$ is a hash function. We want to map the hash of arbitrary message $m$ to a ...
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Greatest hits from previous weeks:
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RSA is not designed to be used on long blocks of plaintext like a block cipher, but I need to use it to send a large (encrypted) message.
How can I do this?
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For example, in RSA, we use this for encryption: $ciphertext = (m^e \mod n)$ and for decryption.
If our message is "hello world", then what number do we have to ...
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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 $...
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When given $p = 5, q = 11, N = 55$ and $e = 17$, I'm trying to compute the RSA private key $d$.
I can calculate $\varphi(N) = 40$, but my lecturer then says to use the extended Euclidean algorithm to ...
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Can somebody explain what the "shared secret" and "password" do when opening/creating a VPN tunnel?
In this specific case I setup a VPN to my Fritz!Box and I had to provide a shared secret (which was ...
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This RFC says the RSA Exponent should be 65537. Why is that number recommended and what are the theoretical and practical impacts & risks of making that number higher or lower?
What are the ...
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Using 7-zip 19.00, on Windows 10 1909, build 18363.592, I encrypted a text file with the contents "hello there" using AES-256 and the password "123". I did this two times, the exact same procedure, ...
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Can you answer these questions?
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There already exist interactive proof protocols with logarithmic communication for proving that a secret multi-exponent $x ∈ Z^{n}_{q}$ for a public multi-exponentiation $P = \textbf{g}^{\textbf{x}} ∈ ...
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Are there any elliptic curves defined over a finite field $\mathrm{GF}(p^k)$ with a subgroup of order $p$ where the discrete log (and preferably DDH) problem is hard? Elliptic curve with prime ...
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I'm struggling to understand the high-level idea of "Verifiable Delay Functions from Supersingular Isogenies and Pairings" (https://eprint.iacr.org/2019/166.pdf) by De Feo et al.
I will ...
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