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1500 questions
30
votes
2 answers
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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30
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4 answers
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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30
votes
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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29
votes
1 answer
ElGamal with elliptic curves
I've searched some information on ECC, but so far I have only found Diffie-Hellman key-exchange implementations using ECC, but I don't want to exchange keys, I want to encrypt & decrypt data like in ElGamal.
I know that ElGamal with elliptic curves…
CriticalError
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29
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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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29
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1 answer
How does HOTP keep in sync?
My understanding of HOTP is that each password is unique and based on a counter.
$$PASSWORD = HOTP_1(K,C)$$
Where $C$ is an incremental counter.
What I wish to know, is how you keep the client and server in sync? Looking at current systems…
mrwooster
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29
votes
1 answer
When to use Argon2i vs Argon2d vs Argon2id?
I've read the manual, and multiple articles / StackExchange posts about this topic, but still can't decide which implementation of Argon2 is best for my use case.
I want to securely encrypt passwords in a database in an unshared environment.
After…
J.D.
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29
votes
1 answer
What data is saved in RSA private key?
What data is saved in RSA private key in openssl? How to view it?
Wikpedia says these variables are saved.
Smit Johnth
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29
votes
5 answers
Other than password hashes, are there other uses for non-reversible crypto
Hashing is useful for checking that an input matches expectations without giving away the stored expected version - so confirming passwords etc.
But are there other use cases? In general, cryptographic storage so data is retrievable seems to be the…
Rory Alsop
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29
votes
2 answers
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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29
votes
5 answers
Why do wireless keyboards only use 128-bit AES? Why not 256?
I've looked for 256-bit AES encrypted wireless keyboards, and apparently they don't exist. Can anybody explain why this is from a cryptographic point of view?
Why wouldn't they just opt-in to the highest standard of encryption, instead of settling…
Jon
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29
votes
1 answer
What is hardened SHA-1, how does it work and how much protection does it offer?
From the shattered website:
You can use the online tool above to submit files and have them checked for a cryptanalytic collision attack on SHA-1. The code behind this was developed by Marc Stevens (CWI) and Dan Shumow (Microsoft) and is publicly…
Maarten Bodewes
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29
votes
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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29
votes
6 answers
Why not authenticate full-disk encryption?
Common FDE software (TrueCrypt, BitLocker, dm-crypt) doesn't authenticate ciphertext stored on the disk. The commonly cited reason is "it would take too much space", reasoning that you would need an authentication tag for every sector and that would…
matejcik
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29
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7 answers
Why is OTP not vulnerable to brute-force attacks?
I saw this question on the book Understanding Cryptography.
At first glance it seems as though an exhaustive key search is possible against an OTP system. Given is a short message, let’s say 5 ASCII characters represented by 40 bit, which was…
Vladmostov
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