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1500 questions
30
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How was the special DES key 0E329232EA6D0D73 found?
The DES key 0E329232EA6D0D73 has the unusual property that decrypting a ciphertext block consisting entirely of zeros gives a plaintext block consisting of eight repetitions of the same byte (0x87).
How was this key originally found?
prim
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What is the recommended number of iterations for Argon2?
I've recompiled my operating system ("LionBSD" based on FreeBSD) to use Argon2i as the default password hashing algorithm in crypt/libcrypt.
I'm wondering what the recommended number of iterations would be?
As an example, OpenBSD uses 8 iterations…
fizk
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What is the effect of the different AES key lengths?
How does a changing key length affects the ciphertext, not only in case of AES, but in general? I know that the key spaces become much larger and the number of rounds in case of AES changes, but is security really that much enhanced that if I choose…
tom
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Why can't I reverse a hash to a possible input?
I'm going to provide “proof” why a hash function can be reversed, and I hope you can tell my why I'm wrong
So, a hash function can be implemented as a series of logic gates. All logic gates can be implemented using only NOT and OR gates. (I'm fairly…
Shelvacu
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How to determine the order of an elliptic curve group from its parameters?
Let $\quad E:\; y^2 = x^3 + ax + b \quad$ be an elliptic curve defined over a finite field $\mathbb F_q$ where $q = p^n$, $a,b \in \mathbb F_q$ and $p \neq 2, 3$. By Hasse's theorem we know that the order of $E(\mathbb F_q)$ is in the range…
user110219
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How strong is the ECDSA algorithm?
Some cryptographic algorithms are as strong as the size of their key is, while other have some weaknesses that limit their strength (such as SHA-1). How strong is the ECDSA algorithm, and does that strength depend on anything (for example, the curve…
ThePiachu
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Which attacks are possible against raw/textbook RSA?
The PKCS#1 standard defines multiple padding schemes for signature generation/verification (EMSA-PSS and EMSA-PKCS1-v1_5), and encryption/decryption (EME-OAEP and the less safe EME-PKCS1-v1_5).
Which attacks are possible on signature…
Maarten Bodewes
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How secure would HMAC-SHA3 be?
It would be possible to implement the HMAC construction with (draft) SHA-3, leading to HMAC-SHA3-224, HMAC-SHA3-256, HMAC-SHA3-384, HMAC-SHA3-512 (the last 3 digits are the output size $\ell$, where $\ell/8$ is the $L$ parameter in HMAC). All that's…
fgrieu
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Can someone explain the ECB Penguin?
I've seen the ECB Penguin used to demonstrate why ECB is not a recommended method of encryption, but I do not understand how this translates to text or passwords.
Aren't the people who create these images comparing apples and oranges?
Josh Bond
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How cryptographically secure was the original WW2 Enigma machine, from a modern viewpoint?
If cryptanalysts today were to crack the original Enigma machine, “how fast” or “how easily” could they do it? What methods would they use?
The original cracking was significantly helped by operator mistakes, like always including the same header,…
vsz
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2 answers
How does a chosen ciphertext attack work, with a simple example?
Can someone please explain - using a simple example - how a chosen ciphertext attack works?
mixkat
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4 answers
Recommended skills for a job in cryptology
First let me apologize if this is an ill posed question. Let me also note that I do not in any way seek a comprehensive answer, simply your thoughts on what makes for a valuable asset to a company like the NSA. I am a Maths student in the US, and I…
Moderat
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What exactly is a negligible (and non-negligible) function?
The mathematical definition of neglible and non-neglible functions is fairly clear-cut, but why they are important and how they are used in cryptography?
Nico Bellic
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Why is asymmetric cryptography bad for huge data?
I've been told that asymmetric cryptography requires that the message to be encrypted be smaller than its key length.
Why is this?
I know about hybrid encryption, which uses symmetric encryption to resolve this problem.
But I still want to know why…
K_X
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1 answer
How are the functions used in cryptographic hash functions chosen?
I'm learning about cryptographic hash functions and I have some questions about the functions used in the compression function.
MD5 uses the following functions:
$f_{1}(B,C,D)=(B\wedge C)\lor(D\wedge \lnot B)$
$f_{2}(B,C,D)=(B\wedge…
Cartman123
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