e-sushi
  • Member for 8 years, 8 months
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Kerckhoffs’ principles – Why should I make my cipher public?
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60 votes

Actually, that wikipedia article you mention in your question already answers your question: It is moderately common for companies and sometimes even standards bodies as in the case of the CSS ...

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Why can't we reverse hashes?
37 votes

Cryptographically secure hashes were specifically build to (among other things) make what you're asking hard! Now, you could try to create an appropriate dictionary of all hashes, hoping to find ...

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How cryptographically secure was the original WW2 Enigma machine, from a modern viewpoint?
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35 votes

What methods would they use? Since WW2, we know the security of Enigma machines was weakened by the reflector, resulting in two problems: No difference between en- and decryption, which means that ...

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Zero knowledge proof protocol example?
29 votes

This is a classical example. Here is the proof system… Bob gives two gloves to Alice so that she is holding one in each hand. Bob can see the gloves at this point, but Bob doesn't tell Alice which ...

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Are there any known collisions for the SHA (1 & 2) family of hash functions?
29 votes

First up, the following table should provide a nice comparison of the SHA algorithms and their status back in 2013, when I fist posted this answer: [38] The theoretical attack on SHA-1 refers ...

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Is it possible to actually verify a “sponge function” security claim?
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28 votes

After spending more than two weeks reading well over 750 pages while checking the following (PDF) documents… Sponge Functions Cryptographic sponge functions Security Analysis of Extended Sponge ...

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Why is SHA-3 a Sponge function?
20 votes

… SHA3 (Bouncycastle) constrains me … Bouncycastle offers the NIST approved, fixed, and standardized output lengths of the keccak sponge function. See, when talking about SHA-3, you're talking about ...

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Cryptography vs Security
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20 votes

The correct answer would be: 1 . “Cryptography is under the security field”. Let me try to explain it a bit… Cryptography Modern cryptography concerns itself with 4 objectives: Confidentiality: ...

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What tests can I do to ensure my random number generator is working correctly?
17 votes

What tests can I do to ensure my PRNG is working correctly? That depends on what exactly you mean by “working correctly”. You can do statistical tests to check for various statistical flaws your ...

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Do any non-US ciphers exist?
16 votes

Plenty of ciphers come out of the USA from government research or selection competitions. AES and DES are examples. Indeed, the US is known from some crypto-related competitions that were/are open to ...

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Is base64 the best two-way hash function to encrypt and transmit a set of integer numbers via the internet?
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16 votes

MD5 – Can I use MD5 as a two-way function? If I can break the data in 64 bit portions, will I be able to recover the original message without a pre-calculated lookup table? MD5 is a hash function, ...

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Did non-military cryptography appear in the 50's and 60's only due to NSA leaks?
15 votes

I won't answer your question up to every detail, as I would have to write a book to answer the pretty broad question to full length. But I'll give you some hints as it would be wrong to let you think ...

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Why is Curve25519 in the GPG “expert” options?
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15 votes

The risk mainly resides in compatibility. See, not all GPG users/systems are updated to the latest version. If you look at the GPG changelogs, you'll notice ECC was first introduced to GPG with ...

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If PGP and GPG both follow the OpenPGP standard, are they 100% compatible in all use cases?
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14 votes

"If PGP and GPG both follow the OpenPGP standard, are they 100% compatible in all use cases?" No, they are not 100% compatible in all use cases, because — depending on the PGP version — there are ...

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Why are cryptography algorithms not exported to certain countries?
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14 votes

Re: "So why limit the export?" The laws you're talking about are generally part of the laws that control the export of weapons and of dual-use goods. Dual-use goods are things that can be used both ...

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Fastest random number generator
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13 votes

The problem with questions that ask for “the fastest” is, that such questions always raise the counter-question: compared to what exactly? Also, your question doesn’t specify if you mean ...

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What changed in PKCS#1 v2.2, and why?
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11 votes

It's merely an update to align the hashing algorithms. There are in fact no real "consequences" which might have any negative impact as the v2.1 schemes are still supported. The positive ...

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Why was the Navajo code not broken by the Japanese in WWII?
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11 votes

Wrapping up my comment as an answer: Imagine you’re a Japanese cryptanalyst in the year 1944. There is no such thing yet called “television”, and you’re still decades away from a wordwide network ...

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How exactly does key whitening manage to increase security?
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11 votes

While it may be confusing, that Wikipedia article is actually correct! Let me try to explain it a bit better… Definition of key whitening Key whitening is an extremely simple technique to make block ...

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The exact difference between a permutation and a substitution
11 votes

Permutation A “P-box” is a permutation of all the bits, meaning: it takes the outputs of all the S-boxes of one round, permutes the bits, and then feeds them into the S-boxes of the next round. A ...

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Cryptographic Challenge: How to Say Something Confidentially to Snowden?
11 votes

First up, I think your question is less something for crypto.SE and would fit better in the security.SE corner. Nevertheless, here goes: ...except his name or identity... That's in itself already ...

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Desirable S-box properties
10 votes

Desirable Properties For simplicity, I’m skipping some of the details here… but the main criteria of a good s-box are: miul It should have balanced component functions, The non-linearity of its ...

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What makes Quantum Cryptography secure?
10 votes

@fgrieu already wrote a little book, so I'll restrict my answer to a minimum to avoid repetitions. Think of this as an extended comment (which indeed wouldn't have fit the comment size limits). What ...

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To what extent is WhatsApp's statement on secure messaging realistic?
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10 votes

So my question is, if they are the ones who encrypt this, then why can't they also decrypt it? Because it’s not them encrypting your message, it’s the App on your device… which is why it’s called End-...

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Why is SHA3 prefixed with SHA despite the fact that it is structurally different from SHA2 and SHA1?
9 votes

SHA… This naming was introduced by NIST (see https://csrc.nist.gov/Projects/Hash-Functions) way back in 1993 during SHA-0 standardization efforts (which ended in SHA-1). SHA stands for Secure Hash ...

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What happens if a SHA-256 input is too long (longer than 512 bits)?
9 votes

If the input message is longer than 512 bits, the input is chopped in “chunks” (read: pieces) with fitting length (512 bits) and those are successively fed to the hash compression function. See, in ...

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What exactly is a “security parameter”?
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9 votes

Quoting the obvious (Wikipedia article about the term “security parameter”.) In cryptography, the security parameter is a variable that measures the input size of the computational problem. Both the ...

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Do I need to use a CSPRNG when creating salts for user accounts?
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9 votes

Answering your question If an attacker have access to a copy of my users database table containing each salt and the related salted password, I can't understand how a CSPRNG would be more secure than ...

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How does Microsoft's BitLocker Recovery Code work?
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9 votes

In my own knowledge, encrypted data can't be decrypted without knowing the key, but BitLocker breaks it. That description indicates you might have misunderstood something there. Bitlocker does not ...

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Is the first version of the Message-Digest algorithm by Ronald Rivest publically available?
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9 votes

Since I have not received any reply from Mr. Rivest's office after bugging them with a total of four emails in four weeks, I have no other option than to give up on hoping I ever receive a reply from ...

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